I made myself a snowball As perfect as could be. I thought I’d keep it as a pet And let it sleep with me. I made it some pajamas And a pillow for its head. Then last night it ran away, But first it wet the bed.
In this article your humble servant will introduce a Japanese plane called the Kiwaganna, meaning “skewed rabbet plane.”
This is an important handplane in common use in Japan, and one we sell, although it’s not well known in the West. So for the benefit our Beloved Customers, I will explain of some of the solutions learned over the years from senior Japanese craftsmen, and acquired during many decades of brutal study at the University of Stoopid, School of Hard Knocks (Lower Outhouse Campus), which may prove useful.
What is the Kiwaganna Handplane?
The Japanese Kiwaganna is written 際鉋 in Chinese characters, and pronounced kee/wha/gah/nah. “Kiwa” means “edge” or “verge,” and “ganna” means handplane.
While the design of the Japanese version is unique, as far as your humble servant is aware, many other versions exist around the globe. The Japanese version has a wooden body, a laminated blade, and is significantly lighter in weight and smaller in volume than its counterparts. It is a superior tool, IMHO, but it can be quirky.
This plane can handle a number of tasks, but it specializes in planing a straight-sided groove or rabbet right up to an edge or line with a clean 90˚ inside corner. A common application is planing the tongue around the perimeter of a board to make the bottom of a drawer, or a panel in frame and panel construction. In construction it is used to pare and clean tenons in timbers and fit finish woodwork, among many other tasks.
Craftsmen who use kiwaganna typically own a two-piece set comprised of a right-hand and left-hand version to deal with tight access and changing grain direction. But the right-hand version is the most popular by far.
This plane is of course used by joiners, cabinetmakers, sashimonoshi and furniture makers, but you would be surprised at how popular it is with carpenters and timber framers for cleaning the 90˚ inside corners of joints such as tenons.
In general, a skewed blade in a rabbet plane provides two benefits. The first is that the reaction forces pushing back on the blade include a vector that tends to push the plane towards the line, edge, inside corner or verge being planed to, making the plane more stable in the cut, an important factor where precision is necessary.
The second and most important benefit of the skewed blade is the smoother cut and reduced tearout it makes possible, especially important when planing cross-grain.
Another benefit the skewed blade provides in the case of the Japanese kiwaganna is the point of the skewed blade penetrating the body of the plane and ending flush with the side of the body, making possible a zero-clearance cut to a line without the extra weight and cost of complicated mechanisms and reinforcing plates. It’s a deceptively simple but clever design.
Points to Keep In Mind
While a simple tool, the kiwaganna often proves frustrating to first-timers. Indeed, your humble servant struggled with kiwaganna for far too long before he figured them out. To avoid similar damage to brain and ego, Beloved Customers that wish to become proficient in using this elegant tool will find it useful to understand the following nine points.
1. First, a brief inspection of the body and the cuts made to receive the blade will show that kiwaganna dai (body) are more fragile than that of regular hiraganna planes, so when adjusting the blade, please use a wooden, plastic or rawhide mallet, not a steel hammer.
2. When removing the blade, strike the dai at the same angle as the blade is inlet into the dai to reduce unnecessary stresses. This means you will hit the top corner of the dai on the side opposite where the blade’s point exits. Clip off and round over this corner of the dai with a knife or chisel to prevent your mallet from chipping the dai. Striking the opposite corner can have bad results.
3. The first step in truing/adjusting the blade of a kiwaganna plane is to sharpen and polish the blade and uragane (chipbreaker) well, make sure they fit each other tightly without a gap near the cutting edge, and check that there is adequate and uniform clearance at the mouth so that shavings flow smoothly without clogging. The skewed nature of the blade and chipbreaker make this difficult to judge, so exercise caution. In many cases, the plane will work just fine, and maybe even better, without its uragane. The uragane has a bevel ground into its pointy corner. Make sure this is not touching the dai when inserted properly. Keep in mind that you will need to periodically grind this bevel down after sharpening the blade every few times or it will touch the dai creating a restriction where shavings will become jammed. When you sharpen the blade, you will also need to resharpen the uragane too to ensure they match each other tightly. Not every time, but once in a while. A lot of people fail to maintain the uragane and then suffer emotional anguish when their plane mysteriously stops working. Mystery solved.
4. The right and left side edges of the blade must fit the retention grooves tightly where they exit the top surface of the dai. If the fit is too loose, the blade will be difficult to keep in alignment, but if the fit is too tight the blade may crack the dai during seasonal shrinkage. Older dai are usually safe, but a plane shipped from a wet Tokyo summer to a hellishly dry Arizona may experience problems. This articleprovides more details about fitting the body to the blade.
When shaving the grooves, work very slowly and carefully. Color the blade’s side edges with pencil lead or marking pen ink. Insert it into the grooves and note the high colored areas. Shave these down just a tiny tiny bit with a very sharp chisel, then insert the blade and check. Repeat as necessary. Don’t create a big gap between the walls of the groove and the sides of the blade (versus face and underside of the blade which must be tightly pinched in the grooves), just make sure the blade is not wedged tightly between the grooves.
5. Check that the “ear” of the blade (corner at the cutting edge opposite the pointy corner) is ground back enough so it does not terminate inside the groove, because if it does, shavings will become jammed.
6. Contact between the back of the blade and the block should not be too high-pressure, otherwise the area on the sole behind the mouth may be pushed out making the plane misbehave, a common problem with this plane. You want even pressure to ensure the blade is stable, but remember that it is the grooves pinching the blade that keeps it in place, not pressure on its back.
7. With the blade fitted to the grooves and most of the pressure relieved from its back, insert the blade. Check that it projects evenly from the mouth its full width. This is very important. If it projects further on one side than the other, resharpen/reshape the cutting edge so it projects perfectly uniformly. This uneven projection is almost always the result of the user unintentionally and gradually changing the angle of the skew over multiple sharpening sessions. Besides projecting uniformly from the mouth (when the sole is at the mouth is perfectly flat), the point of the blade must penetrate the dai (body) and be flush with the outside surface of the sidewall. Failure to get these two subtle details right is the most common cause of failure to perform in the Kiwaganna plane.
8. The mouth opening, in other words the gap between the blade and the sole of the dai where it exits the dai, must be narrow, and even in width, but not closed or skewed, otherwise shavings will jamb in the mouth, another common problem with kiwaganna. If the mouth is not even, use an adjustable steel protractor to match the angle of the blade measured from the side of the dai where the point of the blade exits. Remove the blade and mark the mouth with a sharp marking knife so the mouth is exactly the same angle as the blade. When doing this layout, be extremely careful to make the mouth opening of uniform width to match the cutting edge, but keep the mouth as narrow as possible. Use a sharp chisel to cut to this line making the mouth perfectly uniform. Insert a thin knife blade (or sharpened utility knife blade) into the mouth to shave and clean it after chiseling.
9. There is nothing wrong with leaving the sole perfectly flat instead of having hollowed-out areas typically added to standard hiraganna planes. Just make sure it is truly perfectly flat. I have no problem with using sandpaper on float glass to true the sole of a kiwaganna, but a card scraper is a better tool for the job.
Although we addressed them above, let’s review the two critical factors you must juggle to keep a kiwaganna working well. I’m repeating these points not because I doubt Beloved Customer’s intelligence, but only because repetition improves understanding.
First, maintain the angle of the blade’s skew so that it projects a uniform distance from the mouth (with the mouth/sole flat and true). To do this you must pay more attention when sharpening the blade than is normally necessary. If you get this wrong, nothing will go right.
Second, as mentioned above, to cut into the corner of the rabbet cleanly, the point of the sharpened blade must penetrate the sidewall of the dai and be perfectly flush with the sidewall but without projecting out past the sidewall when the blade is projecting the right amount from the mouth and uniformly across its width. If the skew of the blade is wrong, or the dai is warped or worn, this point will end up being either recessed inside the sidewall or projecting outside it. It needs to be flush with the sidewall. If it is not, you may need to either shave material from the side of the plane (not recommended) or grind down the side edge of the blade near the point, a drastic measure. This is seldom necessary, and when it is, the reason is almost always a badly warped dai.
As you can see, this is a juggling act, but so long as you focus on these two points, and maintain the proper skew angle, all the blades will remain spinning in the air as you grin from ear to ear.
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may my kiwaganna planes all warp to resemble mushy bananas.
In this article your humble servant will introduce a standard woodworking tool which I believe to be unique to Japan, although I have no doubt individual craftsmen around the world have produced versions of it for their own use for hundreds, maybe thousands, of years.
I will explain the jobs this tool is used for, how it is used, how to fettle it, and how to sharpen it. I will also share some first-hand business insight regarding why Japanese women make this tool essential to the joiner in both performing traditional joinery in Japan, as well as the sometimes challenging task of getting paid for his work.
Mr. Spock will also make a brief contribution to the discussion.
Definition & Pronunciation
The Sokozarai Nomi (pronounced Soh/koh/zah/rahi noh/me and written 底浚い鑿 ) translates to “bottom-cleaning chisel.”
It is a simple tool consisting of a differentially-hardened steel shaft, with a small, short, sharp foot formed at the end, attached via a tang to a wooden handle, and secured by a conical ferrule.
The Sokozarai chisel is one of three specialized chisels used specifically for joinery work. Cabinetmakers and furniture makers use it too. Two other specialty joiner chisels are the “Mori Nomi,” which translates to “harpoon chisel,” and “Kama nomi,” which translates to “sickle chisel.” Perhaps we will discuss these in a future article.
A larger version of the sokozarai chisel is used for cleaning the bottom of the larger mortises commonly cut in timber frames.
The Role of the Sokozarai Chisel
The sokozarai chisel is used for two purposes. The first is loosening and removing chips from inside mortises. One simply hooks the offending waste with the chisel’s toe and flips it out.
The second role of the sokozarai chisel is to flatten and even plane mortise bottoms. When set up correctly, it will cut shavings from the bottom of mortises cut in softwood planing them flat and clean.
Indeed, in advanced joinery work, a skillful joiner will plan and execute his joints such that the material left remaining at the bottom of a mortise cut into a stile intended to receive the tenon from a rail is less than 1mm thick, thin enough to allow light to pass through. The ability to routinely cut joints like this, without cutting all the way through, is a mandatory skill of the professional joiner.
I suspect that about now Gentle Reader is forming his elegant eyebrow into an artistic and skeptical arc as he ponders why one would go to the trouble of making clean and pretty the bottom of a hole upon which no one will ever gaze, leaving a paper-thin wall of uniform thickness at the bottom admitting light into a space no one will ever see. Can there possibly be method to this madness? Welcome to traditional Japanese joinery.
Consider that a rough, bumpy floor in a mortise prevents the tenon from seating the last few millimeters, but by planing it flat with a sokozarai chisel, those last few millimeters can be converted to useful space to house maximum-length tenons ensuring maximum resistance to withdrawal and bending forces resulting in strong, slender but durable joinery without adding extra weight. This is a big deal in the case of the slim, flexible frame members found in operable traditional Japanese joinery such as shoji, itado and tsuitate screens, joinery that must satisfy the severe eye and meet the high standards of fit and finish expected by many Japanese women, the most unforgiving consumers in the world.
I don’t know when this detail entered common use, but as Gentle Reader is no doubt aware, the older and more common type of mortise and tenon joint found in joinery worldwide is the through single or double tenon with the tenon’s end exposed at the rail where it is often wedged, a technique that is undoubtedly stronger.
On the other hand, the fully-housed tenon made easier to fabricate using the sokozarai chisel has two advantages over its older, less-refined brother the through-wedged tenon. First, it simply looks better and more elegant when new, and is therefore better able to survive the strict final inspection by the lady of the house thereby more reliably earning the reward of final payment. Hallelujah, pass the bottle brother!
Second, it simply looks better to the eye and feels better in the hand as time goes by because, as the stile shrinks during drier months, the once flush end of the through-tenon won’t project past the surface of the stile creating an unslightly, uncomfortable bump, and during the wetter months it won’t recede back into the mortise leaving an indentation in the stile and an uneven appearance.
These details are not based on esoteric imaginings about quality, but are make or break business decisions essential to avoiding complaints from the same unforgiving Japanese women. And of course, in a country where advertising and representations are routinely and intentionally false (sad but true), word of mouth among sharp-eyed quick-tongued women is critical to a craftsman’s success. Please note that I say this as someone who has has been married to a Japanese woman for 43 years, has lived and worked in Japan for over 30 years, and during those 30 years has had plenty of direct commercial experience working with Japanese women as both customers and team members.
Next time we are sharing a cup of hot cocoa around the evening fire, remind me to tell you the story about two stressful days spent inspecting Thassos marble slabs for a new building’s lobby walls in the company of three Japanese women: an Architect, a Quantity Surveyor, and a Project Manager. All the story lacks is a Rabbi and a Priest to make a rib-splitting joke (ツ)。
Using the Sokozarai Chisel
To use the Sokozarai chisel, and assuming you are right-handed, hold the handle in a fist in your right hand with the blade projecting from the bottom of the fist. Lay the back of the fingers of your left hand on top of and crosswise to the long direction of the mortise. Insert the blade of the chisel into the previously cut mortise hole and press the back of the blade’s neck (opposite the cutting edge of the foot) against the outside edge of your forefinger. Then pinch the blade’s neck between your thumb and forefinger. This is the grip.
To remove loose waste, insert the sokozarai chisel into the mortise hole and move it around gathering chips on the chisel’s toe. Then pull the chisel up and out of the mortise quickly to pop chips out.
To cut loose chips still attached in the mortise hole, press the chisel’s foot to the bottom, move it forward until it snags on irregularities, then rotate the handle towards your body using the forefinger of your left hand as a fulcrum to lever waste out.
To shave the bottom, simply move both hands forward with the bottom of the foot parallel with the intended bottom of the mortise. Developing a sense of the chisel’s action will take practice. Shining a flashlight into the mortise frequently at first will help develop these senses.
To check the depth of the mortise, a specialist kamakebiki, essentially a small router plane, is ideal. But you can make a simple depth gauge by sharpening the edges of the head of a nail or drywall screw, driving or screwing it into a small block of wood, then cutting off and filing the point to avoid ouchies. Using this, you will be able to detect bumps and irregularities remaining on the bottom. Indeed, it too can be used to shave the bottom, but it won’t clean all the way into corners unless you grind the head square or rectangular.
For advanced work, make a slightly undersized test stub tenon with shoulders from hardwood the depth of the finished mortise, and anoint the end with cheap dark lipstick or Vaseline with black oil pigment mixed in. High spots remaining at the bottom of the mortise will be highlighted. With practice, you won’t need this test tenon, but you will still definitely need a sokozarai that is sharp enough to plane the bottom.
Next, let’s consider how to prepare a new sokozarai chisel.
Fettling the Sokozarai Chisel
Unlike most other Japanese chisels, the Sokozari chisel is not laminated construction, but is formed of one piece of differentially-hardened high-carbon steel. Differentially-hardened in this case means that the foot and lower 1/4 of the leg’s length are hardest, becoming progressively softer going up the leg until it is dead soft at the tang. This means the cutting blade, (what your humble servant calls the “foot”) of this chisel will become sharp and stay sharp, but the neck is left softer so it will not snap off, and can even be bent a little to adjust the angle of the foot if necessary.
Low-quality sokozarai have both soft shafts and feet.
Flatten and Polish the Foot’s Bottom
The bottom of the foot needs to be flat and polished, but because of this surface’s narrow width and short length, it can be challenging to accomplish without rounding it over or skewing it.
It often helps to grind a hollow into the foot’s bottom the thickness of a nat’s eyebrow to help speed up the flattening and polishing process. If you use a grinder, be very careful to avoid overheating. It should take no more than one or two brief touches to the wheel.
When flattening and polishing the foot’s bottom surface on diamond plates and stones, it also helps to make a guide block. Cut a slot in the side of a small block of hardwood to house the bent shaft with the bottom of the foot located flush with the block’s bottom surface. Lock the shaft into the guide block with a wedge or a clamp to stabilize it.
The jig in the photos above was made by a Most Beloved Customer who does exceptional high-quality joinery work.
An alternate sharpening jig can made by cutting a crosswise groove, similar to the one shown in the photo below, into the top surface of a stick of scrap wood, perhaps 50mm wide, 200mm long and 20mm thick. The bottom surface of the foot should be almost, but not quite flush with the stick’s edge, projecting the thickness of a piece of paper. Secure this jig to your workbench with a clamp or in a vise, press down on the blade with one hand, and move a sharpening stone along the side of the jig over the foot.
This guide block rides directly on the stone as you flatten and polish the foot’s bottom. Don’t let the foot’s bottom get skewed or rounded over. Work slowly and check constantly. This is a one-time operation.
Once the bottom is flat and polished, you should only need to polish the bottom of the foot on your finishing stone.
Adjust and Polish the Cutting Edge’s Bevel
The bottom of the foot is now flat and pretty, but the angle of the cutting edge is usually still far too steep, and the bevel’s surface is rough. This must be corrected.
Modify the cutting edge’s angle by grinding the bevel on a diamond plate. The final angle you chose for the cutting edge will depend on your preferences and the wood you will be cutting. Steeper angles are more durable. Shallower angles cut better, but dull quicker. 20~24 degrees is usually OK. When I was a young man, I knew professionals who took the bevel angle down to 15 degrees.
You may want to make another narrower guide-block clamping 90 degrees across the the shaft to help hold/stabilize the blade during this operation. When you have adjusted the angle to where you want it to be, then polish it on your sharpening stones. Be careful to avoid skewing it or rounding it over. You want sharp, clean corners.
To routinely sharpen/polish the bevel, hold the chisel in one hand with the bevel face-down on the long side of your sharpening stone. While stabilizing the blade and applying pressure on the bottom of the foot with a fingertip, move the sokozarai chisel back and forth in small strokes being careful to avoid rocking it and rounding it over.
Adjust the Foot’s Length
This step is unnecessary for most applications, but I will touch on it just to be thorough.
The length of the foot is fine as-is for most furniture mortises, but for very tiny mortises as in screens, light fixtures, and small casework, the foot may need to be made shorter. It is not unusual for a tategushi or sashimonoshi to own multiple sokozarai nomi with feet and shafts of different widths and lengths and bevel angles to clean the mortises he makes the most.
Please note that the mortise holes for kumiko members installed in shoji screen and most other types of latticework are shallow and do not require the strength of long tenons, so the mortises are usually cut using mori nomi (harpoon chisels) with a hook on the end to pull out waste quickly, and the bottoms are left rougher.
Beloved Customers that have purchased our chisels, and diligent Gentle Readers that have read this blog, are aware that your humble servant insists our chisels not be used to scrape or lever waste out of joints. The reasons for this are my desire for Beloved Customer’s most excellent chisels to remain as sharp as possible as long as possible, and to avoid chipping the cutting edge. They are, after all, refined cutting tools with sensitive feelings, neither thuggish prybars nor pot-metal screwdrivers.
The Sokozarai chisel was invented specifically as a partner to chisels used for cutting the clean mortises essential to Japanese joinery, and to protect the super-sharp cutting edges of those chisels from damage resulting from barbaric treatment. I encourage you to level-up your joinery skills by procuring and using one. You will be glad you did.
And so I wave farewell until the evening we share a cup of hot cocoa around the irori fire. In the meantime, I am humbly grateful for the honor to remain,
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone by using the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may my sokozarai chisels get athletes feet!
By concentrating on precision, one arrives at technique, but by concentrating on technique one does not arrive at precision.
As mentioned in the previous post in this series, in Japan the mortise chisel is called the “Joiner’s Chisel,” because it is specifically designed for precisely and quickly cutting the many small mortises craftsmen in the joiners trade use in making doors, windows, shoji, screens, furniture and cabinetry.
Why must it cut mortises quickly? Simply because a few seconds of time wasted on each one of many mortises cut during the workday by an uncooperative chisel will quickly add up to hours of lost productivity.
Why must it cut mortises precisely? Simply because defects hidden inside mortises with poor internal tolerances tend to accumulate and too often turn what would otherwise be a well-made piece of furniture or joinery into a rickety old Chinese lawnchair.
In this post we will discuss what to look for in a mortise chisel, and how to correct some typical problems. Most of the concepts discussed in this post are applicable to oiirenomi and atsunomi used for cutting mortises as well, although such chisels lack the same shape advantages.
Klipstein’s Law of Thermodynamics
Just in case Gentle Reader didn’t notice, your humble servant has strong opinions about mortise chisels, partly because I was trained by no-nonsense professionals to routinely cut hundreds of mortises in a single sitting, and partly because bitter experience has taught me the truth that sloppy mortises result in both sloppy products and crushing headaches. Nothing like a bunch of tiny errors when making a series of latticework doors to painfully confirm the validity of Klipstein’s Law of Thermodynamics: “Tolerances inevitably accumulate unidirectionally toward maximum difficulty to assemble.”
Because of this hard-earned experience we have given our blacksmiths specific dimensional tolerance criteria for the mortise chisels they make for us. I can’t always clearly hear what they are muttering in response to my pointed insistence, but it sounds something like “frikin prissy pink princess expects too much of a damned chisel.” Your most humble and obedient servant, however, is much too dignified and polite to respond in so many words, but at such times I think they are stubborn old farts that have never used a mortise chisel. In any case, those who use our mortise chisels benefit from the princess impulse in us.
What to Look For
Mortise chisels are used routinely by only the most skilled craftsmen. Despite their simple appearance, mortise chisels are required to cut to tighter tolerances than other type of chisel, but because they are handmade in the traditional manner without the use of CNC machinery, and because perfection is unattainable in mortal endeavors, they are seldom perfect when new, so Beloved Customer should plan on tuning your mortise chisels before doing serious high-volume work. Indeed, it has long been standard practice among Japanese joiners to modify their chisels and planes to their preferences, and correcting the dimensional imperfections of mortise chisels is at the top of the list, not because they tend to have more imperfections than other chisels, but because more precise work is expected of them.
If you recall some of the mortises you have cut before now you may have noticed that despite your best efforts and forehead-splitting concentration, the sides ended up out-of-square with the workpiece’s top surface, or the side walls were raggedly gouged, or even undercut. These defects are not unusual, and may be due to pernicious pixies, your technique, or perhaps a combination of both, but my money’s on the chisel being the culprit.
Please examine your mortise chisel. If it does not meet the ideal standards in the list below (and it won’t), you should make corrections. You’ll be glad you did. There is a link to a document below that illustrates the ideal mortise chisel as well as some typical problems that may prove useful.
The plane formed by the flat lands surrounding the hollow-ground ura depression should be truly flat and without twist over its entire length from cutting edge to shoulder.
The blade’s width should be consistent over its entire length. Alternately, it is acceptable if the blade’s width becomes just slightly and gradually narrower moving from cutting edge to neck. But not too much. On the other hand, a blade that widens towards the neck is an abomination to be avoided like the spotty-bottom footpads at the California Franchise Tax Board.
The blade’s sides should be flat, planar, free of twist, square to the ura, and square to the blade’s top face. Accordingly, a cross-section taken anywhere across the width of the blade should be rectangular anywhere along its length, with all corners 90°. Picky details, but they can make a big difference in the quality of the finished mortise.
The top face (surface where the brand is stamped) need not be straight, but it must be square to the sides at all points along the blade’s length.
Make no mistake, this is a tall order in a hand-forged tool that has never seen a milling machine, planer, or CNC grinder. Few handmade mortise chisels can meet these standards when new, but these details can make all the difference.
Let’s begin the examination part of this job. You will need a 6~12″ straightedge, a small precision square like the Matsui Precision products we carry, and a vernier caliper.
Record Your Observations
Too often the number of dimensional irregularities that require attention are complicated enough to create confusion. This can result in even experienced people making one irregularity worse, or even generating new problems, while attempting to resolve the initial irregularity, like inadvertently creating more knots while trying to untangle a snarled mess of string.
To avoid confusion, I recommend you make a simple orthogonal hand sketch of your chisel to record irregularities. This sketch should show at least four views of the blade including left and right sides, its face (opposite the hollow-ground ura), and an end view looking towards the cutting edge’s bevel. You may also need to make a few cross-section sketches
Record the results of your examination as annotations and red lines on these sketches to help you plan and execute the work of correcting any problems you may find. There are always a few, and you will need to keep track of each one, and its relationship with the others.
Examine and True the Ura
The first step is to check the ura, the polished lands (flat surfaces) surrounding the hollow-ground depression on the chisel’s back. These must be flat and in the same plane (coplanar). This detail is very important.
A straightedge is good enough for a quick examination, but a more reliable method is to use a granite surface plate. A less expensive and handier option is a simple piece of ⅜” or thicker float glass.
To use a glass surface plate, apply marking pen ink or Dykem to the ura’s lands. Smear a tiny amount of finishing stone mud around on the glass plate. With the entire blade resting on the plate, and finger pressure straight down in the middle of the blade’s face, move it in a oval pattern through the sharpening stone mud. The ink or Dykem at the high spots will be rubbed off, but will remain at the low spots. This will show you where and how much material must be removed to flatten the ura’s lands
Then, true the ura using a diamond plate, diamond stone, sharpening stones, and/or the glass surface plate. This step is not so important in the case of other types of chisels, but a mortise chisel must have a reasonably flat ura. Without a planar ura, the rest of your examination may be inaccurate. The article at this LINK contains a more detailed discussion with pretty pictures.
Do this work carefully. If you heavy-handedly remove too much steel, the useful life of the chisel may be dramatically reduced. This is a one-time operation in the life of most chisels.
Examine the Blade’s Width and Taper
Next, check the width of your mortise chisel measured across the ura using a vernier caliper or micrometer or other reliable gauge. Relative width is what you need to check, not absolute inches or millimeters, unless you expect your chisel to cut precisely-dimensioned mortises, something that is seldom necessary in the real world.
Measure the blade’s width at five or six locations along the cutting edge, in the middle, and near the neck before it narrows. Make a sketch of the blade and annotate these dimensions on it
Use the glass surface plate at this time to check the sides for flatness. The black oxide surface skin will be worn away by the sharpening stone mud marking the high points, but don’t let the change in cosmetic appearance bother you.
Ideally, the blade will be the same width its full length. However, it is usually acceptable if the blade is slightly wider at the cutting edge than near the shoulder. But if it is wider at the shoulder than the cutting end, it will bind in the cut, tend to split the mortise, and the finished mortise will be skiwampus. This must be remedied by grinding the blade on diamond plates and polishing on sharpening stones.
But don’t do anything yet since there are more details you need to examine first. Just make a note on your little sketch.
Examine the Blade’s Sides
Use a good straight-edge to check both sides of the blade’s sides. They must be straight. If they curve in or out it will be difficult to convince it to cut a clean straight mortise. If the blade is banana-shaped, it can’t cut a straight mortise anymore than a politician can tell the truth while his heart beats (it’s rumored that some have hearts).
If the blade’s sides are not straight, they must be corrected by carefully grinding and polishing them. But hold your horses there Hoss, don’t do anything drastic yet, just make a note on your little drawing: there’s still more to check first.
Next check the sides of the blade across their width. They must be either flat (best) or hollow ground (acceptable). If they bulge outwards the blade will bind and can never cut a clean precise mortise, so corrections are absolutely necessary.
Mark any irregularities on your sketch.
Right Angled Sides
The sides of the blade should be at right angles (90°) to the ura lands. If not, the chisel will skew left or right during each cut, a common problem with most chisels. Gentle Reader has no doubt experienced this.
Slightly less than 90˚ may be acceptable (but less than ideal) if both sides are the same angle. If, however, one side is 90˚, for instance, and the opposite side measures 80˚, well that is not good and may require correction.
For now, just mark any irregularities on your sketch.
Examine the Blade’s Face
Next, examine the chisel’s face (the surface with the brand).
This surface need not be straight along its length. It doesn’t even need to be flat across its width, but can even be be hollow or bulging to a minor degree without causing trouble. But you do need to pay attention to two key details.
First, if it is hollow or bulging, the curvature of the bulge or hollow across the blade’s width must be uniform. If not, you should grind it flat.
The second thing to check for is that a line between and touching the corners where the surface of the face meets the blade’s sides must be parallel with the ura. In other words, if you draw a line 90˚ across the width of the face, that line should be parallel with the ura. If it isn’t corrections are necessary.
Why does the relationship of these two surfaces with each other matter? Two reasons. First, if they are not properly aligned, and assuming the ura is flat, it means the blade is thicker in cross-section at either the right side or left side. There is a strong tendency for the bevel and to become skewed during sharpening, with the result that the cutting edge is not square to the center line of the blade’s long axis.
Of course a skewed cutting edge will push the blade to the right or left in the cut, and cannot cut a flat bottom, a serious defect in advanced mortise and tenon work. This deformity can be compensated for with careful attention during sharpening, but you should not have to work so hard. Better to correct the problem now and get it over with once and for all, I promise.
The second and most important reason is that the skewed bevel will cause the blade to dive to the right or left when cutting a mortise ruining precision and gouging the mortise’s walls. This is different from the problem noted in the previous paragraph, although it may seem to be the same. It’s a serious defect in a mortise chisel, one that causes the most self-doubt among craftsmen.
Even the very best blacksmiths frequently fail to give this surface proper attention You are hereby warned: Do not underestimate the importance your chisel’s face.
Examine the Blade’s Corners
Finally, examine the two lines formed by the 90° intersection of the sides and the ura. Are they clean and sharp, or are they ragged, radiused or chamfered? These corner edges serve an important function in dimensioning and shaving the mortise’s side walls. They must be clean and almost acute enough to cut your fingers, but please don’t.
If they are not right, you can correct this now or a little bit at a time during subsequent sharpening sessions. The important thing is to be aware of any defects so you can make corrections, so make a note on your little sketch.
You should now have a sketch describing those areas that need to be corrected. Use it to make a plan. A rough sketch showing how a mortise should should be and common problems is linked to below.
Beloved Customer should keep two important factors in mind in mind when planning and executing corrections to mortise chisels.
First, you should strive to achieve the corrections with the minimum expenditure of time, effort and stone/diamond plate, and while wasting the minimum amount of steel. I am not saying work hard or work fast, but rather to work efficiently.
Second, you should work carefully to avoid creating new problems while attempting to fix existing ones. This is why you need a plan, one that will vary a little with each chisel, to guide you in working efficiently and carefully. Remember, double work takes more than twice the effort, and often wastes lots of expensive steel.
The procedures your humble servant recommends for correcting a mortise chisel (or any chisel used for cutting mortises), based of course on the sketch you prepared, are as follows:
As mentioned above, the first step is to true the ura so it is planar. It need not be perfect at first; Close is good.
After the ura is more-or less planar, grind the right and left side of the blade, whichever is in better shape, straight along its length, flat (or sightly hollow) across its width, and perpendicular to the planar ura. If the angle between the ura and the sides is less than 90°, that’s OK too, so long as the angle of both right and left sides to the ura is the same. An angle here greater than 90° will cause problems and must be corrected. Diamond plates or diamond stones work well for these corrections. Electrical grinders and sanders can be used, but there is a real risk of ruining the temper if you allow the steel to get hotter than is comfortable to touch with your bare finger (seriously), so great caution is necessary. This means working slow and using lots of water.
When one side of the blade is true (perfection is not necessary), grind the opposite side straight along its length, flat (or sightly hollow) across its width, and perpendicular to the planar ura using diamond plates (if necessary). It will be at the same angle with the respect to the ura as the opposite side, of course, because the plane of the ura is the surface against which all others should be measured. Here is where more caution is necessary: pay close attention when grinding this side to make it parallel with the opposite side. If the blade width measured across the ura is slightly wider at the cutting edge than the neck, that’s fine too.. On the other hand, a blade narrower at the cutting edge than near the shoulders is useless for cutting mortises and must be corrected.
Finally, grind the face of the blade (the upper surface with the brand) so that any point along its length is parallel with the ura. It need not be straight or even perfectly flat over its entire length, just parallel with the ura to guide the chisel straight in the cut.
Beloved Customer has no doubt observed that it is entirely possible to succeed in executing one of the corrections in this list while making another worse. Please pay attention. This is why you made the drawing and a plan.
At the conclusion of the steps described in this article, your mortise chisel should now have an ura with all the lands surrounding the hollow-ground swamp forming a single flat plane.
The process of truing the blade’s face will remove some of the black oxide skin. If this changed appearance bothers you, use a chemical bluing/blacking solution such as Birchwood Casey products or those sold by Brownells should work well if used properly. The color may not perfectly match the black oxide finish fresh from the forge, and it won’t be as durable, but it should be less glaring than bright metal.
New chisels are often a bit more brittle than the specified hardness at the extreme edge, and may exhibit small fractures and/or chipping. This is a result of the cutting edge cooling quicker than the rest of the blade during heat treat and tempering.
This is not necessarily a bad thing, but to the contrary is often a sign of a well-made blade. A new chisel that is too hard at the extreme cutting edge when new may well improve after a few sharpenings, but one that is too soft and rolls an edge, or develops a burr, or, heaven forfend, dents in use will almost always be junk forever, unless it was burnt (lost its temper) during grinding, in which case it too may improve with a few sharpenings. I shared the story of Woody and the difficulties he experienced in the “Mystery of the Brittle Blade.” (soon to be out on NetFlix and starring Benedict Cumberbatch (ツ)】
Often the blacksmith or wholesaler will subcontract sharpening job out to a specialist. This practice allows the blacksmith to focus his attention on what he does best, which is a fine thing. But if the sharpener is careless or gets in a frikin hurry and burns the edges while grinding them, without exception the blacksmith gets blamed, resulting not only in an immediate financial loss and wasted time dealing with defective product claims, but a degradation of his valuable reputation. Having experienced this entirely avoidable damage, some blacksmiths, including our honorable plane blacksmith Mr. Nakano, insist on doing their own sharpening, or require the sharpener to work under their eye in their smithy, as does Konobu, to avoid this problem.
Bevel angle is critical to cutting edge durability. I recommend maintaining a bevel angle of at least 27.5°. 35° is even better when cutting harder woods.
You should use a bevel angle gauge of some sort to check the angle during each sharpening session.
You may be surprised how the angle will become gradually smaller with each sharpening if you don’t do this check. Even professionals frequently allow the angle to wander by mistake or through supernatural influences. There are several useful gauges commercially available for this purpose, or you can easily make one from scrap brass or aluminum.
In future articles we will consider the feeding of the Wild Mortise Chisel. They are fastidious diners, after all.
Until then, I have the honor to remain,
If you have questions or would like to learn more about our tools, please click the see the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may my mortise chisels all turn to glass.
Other Articles in “The Care and Feeding of the Wild Mortise Chisel” Series
The purpose of literature is to turn blood into ink.
This is the second article in our series about the Japanese Sumitsubo.
We’ve discussed this tool before, but this time we will examine historical examples as well as an example of an actual sumitsubo ink pot (墨壺 pronounced sue/mee/tsu/boh) currently in your humble servant’s possession. Certainly not a comprehensive explanation by any means, but hopefully it will be informative and mayhap even interesting.
Although the Western chalkbox is now available in Japan, and the Japanese version of this tool is a big improvement over the ones my father taught me how to use when I was a slender “ute,” in Japan the inkline has only been augmented, not replaced, by the chalkbox.
Let’s begin by considering if the sumitsubo is a tool of value to the professional woodworker.
Why Use a Sumitsubo?
Carpenters, woodworkers, steel fabricators, masons and those in many other trades need to mark straight lines for layout and cutting purposes, but what is the longest line one can accurately make using a steel or aluminum straightedge? 1 meter? 4ft? Do you own a truly accurate 1 meter long straightedge or a 4ft long drywall square? How much did it cost? How fragile is it? Will it fit in your nailbag or tool box?
The laser is becoming more and more practical for layout work, but such electronic tools are still not small, light or inexpensive and certainly won’t leave a permanent line. And they have those pesky and expensive batteries that must be constantly recharged and periodically replaced. Very profitable for the manufacturers, of course, but they inevitably end up as poisonous landfill stuffing. When a permanent line is needed for layout or when making long rip cuts with handsaw or circular saw, the snapline is the only viable portable option.
Indeed, the snapline has been the tool for making long, straight layout lines by humans since before recorded history. Sometimes the line has been coated with chalk or limestone dust, sometimes with red soil dust, sometimes with charcoal dust, and in Asia, with a wet ink made from the soot of burned pine tree sap. But humans have such short memories, so most craftsmen younger than 30 years old have forgotten this tool.
The problem with the chalkbox and dry colorants such chalk, charcoal dust or soil is the wide, fuzzy, unclear line they produce.
By comparison, the inkline snaps a relatively narrow, clearly delineated and easy to follow mark on wood, stone and masonry. Not as perfect as a line drawn with a technical pen, of course, but no wider than a laser line and much better than a chalk line.
The second advantage of the inkline is that the line it produces will never get blown away by wind, or be easily smudged. And if you use waterproof ink, one that can be washed away while still wet but becomes indelible once dry, even rain isn’t a problem. And sumitsubo ink has long been available in many colors, including psychedelic hues. Groovy, man!
Does the inkline have downsides? A few, of course. To begin with, you need to be careful to keep the ink bottle tightly closed so it doesn’t leak. Yea, I’ve done that (シ)。
Next, you need to add enough ink to the inkwell to wet the line but not so much it sloshes out making a mess. To paraphrase the ancient Greek poet Hesiod: “Moderation is good.”
And finally, while it can be minimized or even avoided with caution and practice, using an inkline involves getting a bit of ink on at least one fingertip. Fortunately, the Japanese variety doesn’t stain skin like fountain pen or ballpoint pen ink, but washes off quickly and cleanly.
It used to be that a craftsman had to make his own ink by rubbing a stick of sumi ink on a stone with water, a tedious task. Some miyadaiku carpenters still make the ink they use for the first layout lines on important projects in this time-consuming traditional way as a sort of meditative, purifying ceremony, but nowadays, handy ink that won’t separate or mildew is sold cheaply in sturdy plastic bottles. There are of course other ways for a carpenter to obtain Satori.
In any case, your humble servant believes the sumitsubo to be a tool with concrete advantages diligent craftsmen should consider for the toolkit they carry along the sawdust and shaving-strewn path to woodworking enlightenment.
Let’s next next turn our attention to the main subject of this post, the classic, hand-carved wooden sumitsubo.
A Couple of Antique Styles
Not long ago the sumitsubo was a tool each craftsman made for himself by his own hand, giving him incentive to use unusual, even fanciful shapes as an expression of his personal woodcarving skills and artistic sensibilities. Can you judge the skill of the craftsman by his tools? Perhaps not, but it is human nature to do so nonetheless.
Besides the shapes shown in this article, wooden sumitsubo have often been made in the image of animals such as squirrels, rabbits and frogs, insects such as snails and grasshoppers, and even vegetables and plants, not to mention religious images and mythical shapes such as dragons or baku. Many were made to resemble musical instruments such as the three-stringed shamisen, or even boats. Human imagination combined with willing wood and sharp cutting tools can produce fun things.
In the next section we will examine three historical styles that more-or-less illustrate the development of the tool over the centuries.
The Split-tail Sumitsubo
The first style your humble servant would like present is called the “Split Tail” sumitsubo shown in the image below. We discussed this well-preserved example in this post.
I have never owned or used this style of sumitsubo, but friends who have tell me that the excellent air circulation it provides to the reel and resulting mildew reduction is its biggest advantage.
Despite its unique appearance, this style is obsolete for good reasons. Its first design problem is the small inkwell not suited to easy use with a sumisashi pen. And then there’s the total lack of a waist making it easy to fumble. And don’t forget the relatively weak legs and fanciful details easily damaged if the tool is dropped.
The “Ichimonji” Style Sumitsubo
The second style of sumitsubo we will examine is a simpler, more compact one called “ichimonji” 一文字, which translates directly to “The character one” and refers to the shape of the tool being a simple line as in the number one, or “一” as it is written using the Chinese character.
This antique style is compact, easy to make, visually uncluttered, classy and appealing to many craftsmen that make their own sumitsubo, even nowadays. But it too has fallen out of general use for good reasons.
Like the split-tail, the ichimoji sumitsubo has a slab-sided body and no waist making it clumsy to grip in one hand, fine inside the workshop but less than ideal on a construction jobsite.
Another problem is the tiny inkwell which runs out of ink quickly and is clumsy to use with a sumisashi pen.
The reel is obviously on the small size too holding less line than is sometimes needed.
And notice that more than half the reel’s surfaces are enclosed within the body, and that the body has no piercings to encourage air circulation, making mildew growth a problem. At least that was the case before the advent of commercial mildew-resistant ink.
Despite these shortcomings, it is a style appropriate to a workshop environment where the lines snapped are shorter, fumbling is not a concern and the smaller size is useful.
The Genji-style Sumitsubo
The sumitsubo in the photos above and below was hand-carved from zelkova wood (keyaki 欅), a wood popular in Japan for architectural work, carving and furniture. Most exposed woodwork seen in Buddhist temples in Japan is zelkova. It has a pronounced grain, nice color, carves nicely, and is fairly rot-resistant, although not nearly as much as Hinoki, the wood preferred for Shinto shrines. The brandname of this example is “Tsubo Gen” 壺源 .
Back in storage in the US I have a medium-grade wooden Genji sumitsubo I bought in Japan and used for many years, but I purchased the tool pictured here in Tokyo 9 or 10 years ago and have not used it at all, as you can tell from its pristine condition.
It was finished with lacquer when I purchased it so I refinished it with Cashew brand natural urethane last year just for vanity’s sake.
I normally mount this tool inside the lid of my toolchest to please the eye, attract good luck, and fend off malevolent iron pixies. It has accomplished these tasks well probably due to the noble efforts of the scowling little turtle; The crane doesn’t seem to impress them, I fear. We will discuss the lucky aspects of this tool below.
This is a Tokyo version of the Genji sumitsubo as witnessed by the brass crank used for spooling in line. In Western Japan, cranks are not as common, so craftsmen pass the palm of their hand over the top of the reel to spool in line. I’m not sure which style is most efficient.
It is a clever design evolution that resolves the shortcomings of the older designs. I see the following six advantages in this design.
The first advantage to the Genji design is the narrower waist between the reel and inkwell that makes it much easier to securely grip the tool in one hand while at the same time tensioning the line or even braking the reel with the same hand. This is a huge improvement over all older styles.
The second advantage is the wider, larger-capacity inkwell which stays wetter longer and makes it easy to use with a sumisashi for applying layout and designation marks on timbers. It also provides a stable place to rest the sumishashi when not in use without setting it down in the dirt or stuffing it in a nailbag pocket (and making everything else in the pocket wet with black ink).
The third advantage is the larger-diameter inkline reel which contains more line while at the same time being quicker to reel in.
The fourth advantage to this design is the improved air circulation to the line stored on the reel thereby reducing mildew growth. Not only does the wooden reel project further out of the top of the body, but it is also pierced with carved spokes exposing the sides and even the underside of the line on the reel. In addition, the body is pierced at the sides and even the underside to further improve air circulation and reduce weight.
The fifth advantage is that, despite the larger-capacity inkwell and reel, much unnecessary material has been carved away making the tool relatively lighter in weight.
And finally, the sixth advantage of this design is the lucky symbols frequently carved into the body. We all need a little luck.
Typical of many things Japanese, a lot of thought went into these subtle design improvements.
One of the most common lucky symbols in Japanese mythology is the crane, said to live 1,000 years and bring good luck, prosperity and happiness. The Japanese love these tall cranes with their little red caps and graceful mating dances. Here’s a link to an interesting video about them.
The turtle, especially the sea turtle, is also considered extremely lucky but for a longer 10,000 years. The turtle carved into sumitsubo usually has a trailing skirt of seaweed flowing from its shell, as does mine, evidence of its great age and accumulated wisdom.
Dragons, Chinese Lions, Baku and other mythological creatures of good fortune are also used.
I’m not a superstitious guy, but I’ll keep my crane and scowling turtle close by just in case, thank you very much.
The First Modern Variant: The Plastic Sumitsubo
The first sumitsubo I owned I bought in the city of Matsuyama on Shikoku Island in 1978. Having few funds, I was unable to afford the hand-carved wooden one I admired, so I bought a plastic version of the Genji-style wooden sumitsubo identical to the photo right.
Being made of plastic using molds from a hand-carved wooden model, it looks exactly like the traditional wooden sumitsubo except for the color, texture and weight. Offsetting the marvelously unsatisfying feel in the hand, this tool has several serious advantages.
The first advantage is its low cost. It can be purchased new for around ¥2,100.
The second advantage is the toughness of plastic. A wooden sumitsubo will at least be dinged and dented if dropped and may even break, but this one will take a likin and keep on tikin. I have seen one survive being run over by a truck.
The third advantage is the certain fact that the inkwell will never develop cracks or leak, unless you notch it with a circular saw or melt a hole in it with welding sparks (yes, I’ve seen that done too (シ)).
And it still has the elegant lucky crane to bring happiness and productivity and his snappy little turtle buddy to keep Murphy away. What more could you want? Egg in your beer?
The classic wooden sumitsubo may not be the most practical tool in the field, but it is the one selected by master carpenters when doing layout, not only because of the tactile experience it provides, but because the tool reflects on the craftsman that uses it. Face it, like a light-blue polyester leisure suit worn with white belt and white shoes, the plastic sumitsubo may be practical but it is simply undignified.
We will discuss some other Modern Variants in a future post.
How to Use the Sumitsubo
The image below is not only historical, but instructive in ways to use the sumitsubo. It depicts an ongoing construction project at the Kasuka Shrine during Japan’s Kamakura period (1192~1333) where carpenters are preparing lumber and timbers to be incorporated into the shrine.
Please notice the “Split-tail” sumitsubo resting on the ground near the feet of the carpenter on the bottom-left, and in the hands of both carpenters to the right.
The team of two carpenters in the lower half of the image are using an adze to keep the log from rolling away and their squares to layout plumb lines on both ends of the log. The carpenter on the bottom right is orienting his square in the vertical direction by squinting at a plumb line made using his inkline and sumitsubo, while the carpenter at the bottom left is matching his square to that of his partner by sighting along the horizontal short tongue of his square. Winding sticks? We don’t need no stinkin winding sticks!
In his right hand you can see the bamboo sumisashi ink pen he is using to mark the plumb line, not doubt with ink from his sumitsubo’s inkwell.
The carpenter and his helper in the upper half of the image are using a sumitsubo to mark the edges of a split plank. The scruffy helper at the left holds the line in place to a mark, while the carpenter in the fancy hat lifts the line with his fingertips and releases it to snap a line of ink onto the plank.
Maybe it’s his hat, but he appears to be laughing like a maniac at some joke I wish the artist had recorded in this image since there is so little humor left in our dry-as-dust politically-correct world ruled by willfully brain-dead, corrupt zombie scolds. No doubt Gentle Reader has met a few of these zombie scolds who tried to suck every ounce of joy from him. Never fear, because I am convinced friend crane and friend turtle can discourage them from climbing the tree to get at us.
The steps to using the wooden sumitsubo are described in the photos below.
Here are links to a few GooberTube videos of guys using sumitsubo. My old master would have been disappointed with their techniques, especially with how they let the sumishashi get in the way, with one guy even sticking it in his mouth to free his hands (egads!). But there’s no denying they are getting the job done. Video 1,Video 2.
Both of these gentlemen are using sumitsubo without cranks, strongly suggesting they are located in Western Japan and not the Tokyo area.
I’m sure Gentle Reader will agree that the hand-carved wooden sumitsubo adds class and dignity to a craftsman’s work, and maybe even a little good luck.
In the next post in this series about the Japanese sumitsubo we will take a look at the most recent evolution of the tool. They look like something designed by Cylons, but they are serious, effective tools nonetheless.
Until we meet again, I have the honor to remain,
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with all Gentle Readers using the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, thuggish Twitter, nor an Assistant Director of the FBI and so won’t sell, share, or profitably “misplace” your information. May my scowling lucky turtle nip notches in my fingers if I lie.
And now at last it comes. You will give me the Ring freely! In place of the Dark Lord you will set up a Queen. And I shall not be dark, but beautiful and terrible as the Morning and the Night! Fair as the Sea and the Sun and the Snow upon the Mountain! Dreadful as the Storm and the Lightning! Stronger than the foundations of the earth. All shall love me and despair!
J. R. R. Tolkien
This article is a continuation of, and probably the conclusion to, our “Sharpening Japanese Tools” series. The last postwas one year ago and gave an example of how to employ the lessons taught in the previous 29 posts. At that time, your humble servant promised to discuss the subjects of this post at a later date. It’s later.
Why the delay? Simply because I am an excessively compassionate sumbitch who wanted Beloved Customers who hadn’t already figured out plane blade sharpening on their own to become proficient at regular sharpening operations before worrying about something as bizarre as wacking hard steel blades with hard steel hammers. After all, in the words of Miss Benatar, it’s sometimes a heartbreaker.
But now with the blog teetering on the loose and crumbly edge of the rabbit hole that is the Japanese handplane, we have the choice of either gliding gracefully into its depths or clumsily tumbling down ass over tea kettle (oh my!). Alas, we can tarry in this precarious position no longer.
With his article we will begin our graceful swan-like journey by studying a matched set of operations Beloved Customers need to master to become proficient at maintaining Japanese woodworking blades, one called “Uradashi,” and a related operation called “Uraoshi. If you already have these skills, accept my highest praise. The target audience for this post, however, is those that don’t have experience with uradashi and uraoshi as well as those that want to review and improve the skills they already have.
So spread your wings and fly, my brave cygnets!
Beloved Customers should already be aware of the hollow-ground “uratsuki,” typical to Japanese chisel and plane blades. If not, please review the article at this link.
Uradashi is pronounced oo/rah/dah/she and written 浦出し in the Chinese characters as they are used in Japan. These characters translate directly to “push-out the ura.”
Uraoshi is pronounced oo/rah/oh/she and written 浦押しwhich translates directly to “press the ura.”
These two maintenance operations are performed to restore the blade’s cutting edge to useful condition when the thin land at the cutting edge is almost worn out. We will discuss the why and how below.
Before we start pecking on steel, let’s consider our sharpening strategy.
Professional-grade blades are not only expensive, they are difficult to make, hard to find, and require an investment of time and effort from the user if they are to deliver high-performance results over many years. To minimize the required expenditure of time and effort, and to maximize the results delivered, we need more than just technique, we need a maintenance strategy.
In previous posts in this series we have discussed multiple strategies, some physical, some psychological, and even a few supernatural ones. The following is one I strongly urge Beloved Customers to adopt:
Get the ura in good fettle, and then;
Avoid working the ura on anything but one’s finest-grit sharpening stone thereafter, (with the exception of uraoshi following uradashi, of course).
The ura is formed by grinding the lamination of extra-hard high-carbon steel to form a hollow area. Because hard steel is time-consuming to abrade, a wise craftsman will work to keep the ura as deep as possible, and the flat lands surrounding the hollow-ground ura as narrow as possible, as long as possible, thereby minimizing the area of hard steel that must be abraded with each sharpening.
But no matter how careful we are to preserve the ura, sharpening the bevel makes the blade incrementally shorter, so the day will come, at least in the case of plane blades, when the land at the ura immediately behind the cutting edge, called the “itoura,” (pronounced ee/toh/oo/rah, meaning “ thread ura” ) becomes as thin as a thread. Once it disappears, the blade will no longer function. This is the only drawback to the Japanese ura feature, and can only be solved by bending brittle steel.
Bending Hard Steel
The goal of uradashi is to cause the lamination of hard steel at the cutting edge to bend towards the ura so that when we subsequently abrade the bent portion of the ura the itoura land will be restored.
Now if you think about this for a second you will realize that trying to bend a thin plate of steel hardened to Rc65~66 without snapping it is a fool’s errand. In the case of Japanese blades it is possible to accomplish but only because of the thicker, supporting layer of soft low-carbon/no-carbon iron, called the “jigane,” to which the hard steel layer is laminated.
Your humble servant struggled at first with uradashi, in part because every explanation I read about the process in both English and Japanese was written by people who either didn’t really know what they were talking about, or were too lazy to explain it well. Some years, several broken blades, and much heartbreak later I finally figured it out. Better information is available nowadays, but there is still plenty of BS out there to shovel.
The first key point to understand and always remember is that uradashi is not about using a hammer to bend the hard steel layer; Never ever ever never touch this steel with your hammer! I forbid it on pain of 20 lashes with a wet noodle.
Instead, the goal is to peck on the soft iron jigane layer of the laminated blade at the bevel, as described below, deforming it and causing it to expand.
The jigane would normally just deform away from the hammer’s impact point, but the hard steel hagane lamination on the ura side of the blade restrains it causing the entire blade at the cutting bevel to curve in the direction of the ura without snapping or cracking. This is another aspect of the blacksmith’s magic unique to the Japanese plane blade.
The second key point you need to grasp around the neck with both hands and dig your Jimmy Choos deep into is that it is indeed a fool’s errand to try to bend the soft iron lamination by the power of your mighty arm, Oh Lord of Thunder. No, we must be as clever as Loki.
So, how do we cleverly do this job, and what tools should we use?
You will need the following tools to properly perform uradashi and uraoshi on a blade:
A small hammer. Great force is neither necessary nor useful, but you must be able to control this hammer very precisely, so the lighter the better. One with a pointy end like a funate or a Yamakichi or a corner of the thin end of a Warrington hammer is ideal because it focuses maximum pressure on a small area, deforming the jigane efficiently. A small, pointy hammer also makes it easier guide and control the hammer to ensure precise impacts. And control matters a lot because if you miss and strike the hard steel at the cutting edge it will be damaged and bitter tears will flow. Consider yourself duly warned, Oh Might Thor;
An anvil of sorts. This can be any piece of steel with some mass and with a rounded-over corner. A piece of railroad track is great. I use the face of a small sledge-hammer clamped in my vise. A sharp corner is not good, so grind or file one and then smooth it. A piece of thin postcard material glued to this rounded corner help keeps the blade from slipping;
A small square or straightedge;
A marking pen or scribe to mark the “target area” on the bevel;
A rough diamond plate/stone or a mild-steel kanaban plate + carborundum powder;
Parking pen or Dykem for coloring the ura’s lands;
Regular sharpening tools (stones, water, etc.).
Target Area Layout
Let’s begin by laying out the target area on the soft iron jigane at the blade’s bevel with a marking pen. Or you can scratch lines into the jigane with a metal scribe. This target area will indicate the area you will peck with your little hammer producing many small dents. You must not strike outside this target area even if tempted with donuts.
The dents you will make with your little hammer need to be limited to a band on the jigane parallel to the cutting edge and beginning 2~3mm from where the jigane lamination begins extending to the end of the jigane lamination at the blade’s back, in the case of plane blades, or the face where the brandname is engraved in the case of chisel blades. Make a line with your scribe or marking pen the full width of the bevel at this distance from and parallel to the cutting edge. Everything above this line in the direction of the blade’s back, in the case of plane blades, or the face where the brandname is engraved in the case of chisels and knives, is the primary target area. Make sure you get this right.
The dents need to extend across the full width of the jigane layer, except where the corners (ears) have been ground to a bevel at the right and left end of the blade, so the right and left limits of the target area are delineated by the ears.
Although we need to tap the full width of the blade to avoid stress concentrations, there is nothing to be gained by trying to bend the far right and left corners of the blade, so we want to focus approximately 2/3rds of our hammer impacts and the resulting dents near the center 1/3 of the blade’s width. Mark the right and left limits of this central area on your blade with a marking pen or scribe.
If you are right handed, hold the blade in your left hand with your index finger extended and pressed against the ura parallel with the cutting edge, and about 5~10mm away from it. Press down with your thumb on the blade’s back clamping the blade between your thumb and the side of your index finger. Your other fingers should support the blade from the ura side.
Your index finger will be the fence that keeps the blade in proper alignment during the tapping-out process.
Next, we need to figure out how to align and move the blade on the anvil, as well as where to place hammer blows in relation to the blade and anvil.
Manipulating the Blade on the Anvil
Place the blade’s ura on the rounded corner of your anvil. You may want to tape or glue a piece of thin cardboard, postcard, or manila file folder to the anvil’s corner not so much as a cushion but to help prevent the blade from slipping, but this is not mandatory.
Adjust the distance between your extended index finger and the cutting edge as necessary so your finger is touching the anvil stabilizing its position, and so you can slide the blade to the left and right indexing off your finger to keep the target area in proper alignment.
Next, while still in position facing your anvil and with hammer in hand, move the blade aside and tap the rounded corner of your anvil with your hammer lightly. Memorize this location and your position because every tap from now on must be aimed at this same exact spot on the anvil.
The Tap Dance
The time has come to begin the dance.
Reposition the blade on the anvil and use your little hammer to tap the soft jigane layer at the bevel (only the jigane!) in the target area you marked earlier making a row of small dents in it.
These small dents don’t need to be pretty or uniform. Be patient because you may need to make hundreds of pecks, each one quite precisely.
Here is the key point to understand: You want each little dent to cause the jigane to deform and expand in length and width a tiny bit, gradually, until a significant degree of deformation accumulates. The hard steel layer, however, will constrain the jigane layer from expanding, causing the blade to bend, and causing the hard steel layer to deflect and curve towards the ura, bending it without breaking it. It doesn’t seem possible at first, but I promise it will happen, so please be patient.
The trick then is to use the grip described above with your forefinger indexing the blade against the anvil while moving your hand, along with the blade, a tiny bit right or left with each strike, with the each point of impact firmly supported on the anvil, in-line with the hammer blow, thereby squishing the jigane between hammer and anvil. In this way, since the hammer is always aimed at the same exact point on the anvil, you don’t need to worry about realigning it with each blow, removing several difficult-to-control variables from the tap dance at once.
Remember, keep the hammer and anvil precisely aligned, and move the blade left and right, not the hammer. It helps to touch the inside of the elbow of the arm using the hammer against your side in a fixed location to help maintain a consistent hammer swing and distance. Until you have mastered consistency, speed is risky.
Another key point to understand is that, if the point of impact of your little hammer is not directly in-line with the point where the ura on the opposite side of the blade is touching the anvil, the force of the hammer’s impact will tend to cause the blade to jump and wiggle around instead of deforming the jigane. This wastes time and energy and makes it difficult to make precise taps.
Here’s a video of Eleanor Powell tapping away with great control, and with the aid of her faithful Fido. I don’t recommend including a benchdog in your tapping-out routine other than as a deterrent to any pernicious pixies lurking in your workshop eager to cause you to miss with your hammer and chip your blade. Evil pixies!
Here’s a video of Sarah Reich tap dancing with every strike landing precisely in the target area. I need to get a pair of shiny red lycra pants like her to go with my most excellent aluminum foil hat with the curly copper wires and red fringe. Do you think they would make my butt look huge?
Remember, force is neither necessary nor useful. The goals is to make many precisely aligned tiny taps producing many small deformations in the target area, with no impacts on the hard steel layer.
We talked about “dents” above. If you are using a round-faced hammer, those dents will be little crescents. If you use a hammer with a tiny striking face on one end like a Yamakichi or Funate, that tiny face will dig into the metal making ugly little peck marks instead of pretty little crescents. I have used all varieties of hammers but prefer the ones with pointy ends because they impact face is small and, it seems to me, easier to control. Six of one half-dozen of the other.
But remember that we will abrade away all those dents/craters after a few sharpening sessions, so appearance is of zero importance.
The Goldilocks Itoura
The goal, of course, is to bend the blade at the ura land just behind the cutting edge enough to create a useful, flat ura. But how wide should the itoura be when the process is complete? Among plane connoisseurs a narrow itoura is, like a willowy super model, considered a thing of beauty. By narrow I mean some where around 0.50~1.0mm.
A narrow itoura does indeed look sexy, so much so that fashion-conscious plane blade blacksmiths make a skinny ura a point of pride. And, in fact, a bulimic itoura makes it easier and quicker to sharpen the blade because the square millimeters of hard steel one must abrade/polish is minimal compared to a wider itoura.
The downside to the super-model itoura is that it wears out sooner, making it high maintenance. Now, I’m not suggesting that if your plane blade has a super-skinny itoura it will demand weekly spa visits, twice monthly trips on a G700 jet to the Vienna Opera, annual ski holidays in Verbier, and bi-annual boob jobs, but there is no doubt you will need to do the uradashi tap-dance more often. Shiny lycra pants are optional, but ooh sooo sexy.
On the other hand, a wider itoura of 3~4mm has some advantages too. It’s easier to fit the chipbreaker (uragane), and you don’t need to do uradashi/uraoshi as often. Much wider than this, however, and I find it can be difficult to get a screaming-sharp edge at times. Moderation in all things, I guess.
I don’t know how to describe when to stop tapping-out the ura to obtain a good width for your itorura because every blade is a little different, but after doing it a few times you will develop a sense of when enough is enough. However, to develop that sense you should make frequent checks on your tapping-out progress by placing your handy dandy straightedge or square right on the itoura parallel to the cutting edge and sighting between the blade and the straightedge/square with a strong light shining at the gap. You will be able to see the itoura gradually bulge upwards at the center. Even a little bit of a bulge will give you a useful itoura, so don’t get carried away.
Once the tap dance is done, we need to grind down the ura to form a new itoura.
The traditional method is to use the mild steel kanaban lapping plate mentioned above, although any true lapping plate will work. One sprinkles a small amount of carborundum powder on the plate along with a little water, and works the ura side to side grinding down the bulged area to make a flat.
The problem with using lapping plates and carborundum powder is that not only is it a messy process, but unless you are careful to keep the right amount of wet grit on the plate, the results tend to be a tad irregular. I recommend using diamond plates or diamond stones (like those made by Naniwa) because they produce more consistent results quicker.
Whether you use a kanaban lapping plate or a diamond plate/stone, it is important to focus pressure on the thin area where you need the itoura to develop. Pressure anywhere else is not helpful, but only wears out the itoura prematurely.
Here is wisdom: When they first attempt uraoshi most people try to stabilize the blade by applying uniform pressure across the back of the blade. This seems to makes perfect sense, but it always results in grinding a nasty little trench in the ura where it touches the extreme edge of the kanaban or diamond plate. Remember, the uraoshi process tapped out a bit of metal right at the cutting edge, and mostly at its center. This is what you need to abrade, NOT the right and left lands of the ura, and certainly no more than 3~4mm from the cutting edge. So carefully focus the pressure you apply during uraoshi only on the thin area where you need to restore the uraoshi.
Some people like to apply a thin strip of paste wax, perhaps 3~4mm wide, on the edge of their kanaban or diamond plate to prevent it from digging ugly trenches in their beautiful and delicate side lands. Others like to apply a thin strip of mylar tape at the same place for the same reason. These techniques all work, but professional sharpeners don’t use them because they know how to apply pressure correctly.
After the itoura has been restored (perfection is not necessary), polish the blade using your normal sharpening routine.
Chisel Blades Versus Plane Blades
Uraoshi and uradashi are operations typically, but not exclusively, performed on plane blades. About the only time chisels need to have uradashi performed is to restore the itoura after the blade receives major damage, like a big chip, a sad event all users of Japanese tools experience from time to time
There is a structural difference between plane blades and chisel blades one must understand when considering performing uradashi on a chisel blade.
Plane blades have a steel lamination that is more-or-less uniform in thickness because that’s all that’s necessary. Chisel blades, on the other hand, are subject to much higher bending stresses than plane blades, so to prevent yielding and failure, traditional chisels are forge-laminated with the steel lamination wrapped up the right and left sides of the blade, forming something akin to a structural steel U-channel, producing a higher moment of inertia, and therefore greater strength and rigidity,
Because of this additional strength, chisel blades are more difficult to bend at the right and left sides using uradashi techniques compared to plane blades. Indeed, they may break if you try.
Since you can hope to safely bend the steel lamination only in areas away from the more rigid sides, uradashi operations on narrow chisel blades will go as smoothly as throwing a cat through a screen door. I wouldn’t even try it on any chisel narrower than 18mm. Beloved Customers have been warned.
If you feel compelled to attempt uradashi on a chisel blade, my only advice is don’t peck within 3mm of the right and left sides.
With this article, our Sharpening Japanese Tools Series is complete (probably). Your humble servant hopes it has been helpful. If Beloved Customer had the patience to read it all, and the clairvoyant ability needed to understand most of it, then you know a heck of a lot more on the subject of sharpening than I did when I started the journey. At least you have received some great ideas for sexy new additions to your simply mahvelous woodworking wardrobe!
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may Iron Pixies pass gas in my cornflakes every morning.
I warn you, if you bore me, I shall take my revenge.
Your most humble and obedient servant has received many requests over the years for explanations about how to setup, adjust, maintain and use Japanese planes. It’s a big subject, enough to fill volumes and volumes, and an important one to woodworkers, but I will try to explain in enough generality that new guys can follow, and in enough detail that professionals may glean something useful.
In this series we will discuss how to adjust a Japanese plane so it works well, how to tune it to increase performance, how to treat the body to reduce warpage and keep it looking good, how to deal with normal wear and tear, how to periodically tap out and dress the ura during sharpening, and of course how to use a Japanese plane.
This last subject is extremely simple but one many amateur users of Japanese planes and most users overseas get wrong. It happens so frequently that I am confident the improvement in Beloved Customer’s personal performance with Japanese planes will improve dramatically from this last subject alone.
The problem with Japanese planes is that, while they are simple tools, they are at the same time more sophisticated than appearances suggests. Dealing with these subtle details without properly understanding them leaves many as confused as a ball of yarn among a dozen big-eyed kittens, so to avoid having too many strands running all over the place, let’s start with the basics, namely how to adjust them. For purposes of this discussion, we will assume our plane is in good fettle to begin with.
Preparing the Body
Although this is not an issue in the case of the planes C&S Tools purveys, Beloved Customer will want to inspect their plane, and perhaps make a few modifications to the body before playing with the blade too much.
When removing the blade or reducing the cutting edge’s projection through the mouth, we need to strike the body on the 90˚ intersection between the flat end of the plane’s body and its top surface. Accordingly we need cut a chamfer at this location to prevent damage to the body. How wide? 3~5mm is a good range. While you are at it, cut off the corners formed at the right and left sides of this chamfer.
This is a one-time operation.
You also need to cut chamfers on the four edges at the right and left sides (long direction) of your plane’s sole. These chamfers have two purposes. First, to prevent the edges of the sole from chipping. Second, to make a small gap for your fingers to grip when lifting up the plane.
As the sole wears, Beloved Customers will need to be refresh the chamfers at the sole from time to time, so further explanation is necessary.
Some people like big, wide 45˚ chamfers at these locations. Your humble servant has even seen country bumpkins cut these wide chamfers and then carve unsightly grooves resembling a shark’s grin leading from the sides of the mouth to these chamfers for shavings to escape into. Codswallop!
Why is this a problem, you ask? Because the thinnest, weakest portion of any wooden plane’s body is the sidewalls right at the mouth. This is also where most warpage originates, so please don’t weaken it more than is absolutely necessary by cutting unnecessarily-wide chamfers.
In addition, wood removed from the sole by cutting overly-large chamfers reduces the bearing area of wood on the surface being planed accelerating wear on the sole. Keep these chamfers narrow at 2~4mm and a max angle measured from the sole of 25~29˚ More than this is unnecessary and possibly harmful.
A chamfer is not necessary at the trailing end of the sole so long as you have the self control to not strike the sole with your mallet.
Do not cut a chamfer at the leading edge of the sole as it will guide sawdust and shavings between the sole and the surface you are planing. Pas bien.
Apply a small chamfer on the front and side edges of the top surface, just enough to prevent chipping. 45˚ chamfers are fine, but a roundover (bozumen 坊主面 which translates to “Priest’s edge,” probably in reference to the bald head of Buddhist priests in Japan) is a friendlier, more elegant edge treatment, IMHO. Your choice.
Hammer or Mallet
In order to use a plane of any kind, one must remove the blade to sharpen it, and then re-install the blade and adjust its projection from the body’s mouth to produce a wood shaving of the desired thickness.
Like most wooden-bodied planes, one adjusts a Japanese plane by striking it with a hammer or mallet. To drive the blade further into the wooden body (called a “dai” 台 in Japanese) when installing the blade or when increasing the depth of cut, one taps the head of the blade down into the wooden body. Pretty straightforward. But like most things in life, there are both clever and stupid ways to get even simple jobs done. Let’s consider some of the clever ones, shall we?
You can use either a metallic hammer or a mallet made of wood, plastic or even rawhide to tap the blade or dai during these operations. They all work just fine, but there are long-term consequences to this selection you need to be aware of.
In Japan a steel hammer is traditionally used by carpenters to adjust planes. Without a doubt it’s convenient and effective, but there are some serious downsides to using a steel hammer you may not realize. Those include:
A steel hammer always mushrooms the blade’s head, without exception;
A steel hammer always dings the blade’s pretty face when adjusting the chipbreaker, and most critically;
After many strikes, the high impact forces of steel hammers impart will often crack and even split the wooden body (dai). Ouch!
A deformed and ugly blade may not be a tragedy, but a split body is an expensive and time-wasting catastrophe, especially if you are a professional that needs his planes to keep cutting.
There may be Beloved Customers who will say: “But I’ve seen Japanese craftsmen using steel hammers to adjust their planes, so it can’t be wrong.” The first part of this observation may be true, but the last bit isn’t. The undeniable truth is that steel hammers have created many ugly, dinged, bent, and mushroomed blades, as well cracked and splintered many dai, mostly unnecessarily. Some carpenters are especially abusive of their poor planes, sorry to say, but not all Japanese craftsmen are so inured to the suffering of their tools.
C&S Tool’s planes don’t deserve such violent abuse, so we recommend Beloved Customers use a wooden mallet to adjust them. Without exception. A plastic or rawhide mallet with a wooden handle will work just as well.
Removing the Blade and Chipbreaker
Both the blade and chipbreaker are removed by tapping the chamfered corner of the block behind the blade with a mallet. We discussed this chamfer above.
It is of course possible to loosen the blade by tapping flat on the flat tail end of the block, but there is a risk of striking the bottom edge and deforming or even chipping the sole. Best avoided altogether.
The physics work best when the mallet impacts are applied in a direction more or less parallel with the blade’s long axis.
Your humble servant prefers to make this striking chamfer wide to minimize deformation of the body, but this is a personal preference. If your plane’s body is not chamfered, creating it is is an important first step.
The chipbreaker (uragane) must be removed before the blade, but you need to be careful to prevent two unfortunate things from occurring during this process. The first thing to avoid is the chipbreaker jumping out of the block providing Murphy the opportunity for gleeful mischief.
The second thing to avoid is the blade backing out of the body further/faster than the chipbreaker causing the chipbreaker to ride over the blade’s extreme cutting edge dulling it. This point is one newbies often overlook until they wonder why the pretty cutting edge they just sharpened is dinged even before they begin cutting.
How does one keep blade and chipbreaker under control? Your humble servant recommends pressing a forefinger onto the chipbreaker and applying pressure upwards when removing it. Do the same on the face of the blade when its turn comes/ as shown in the photos below.
Once the chipbreaker is loose, remove it and go back to tapping the body to loosen the blade further. Continue to apply light pressure to the blade’s face to better monitor the blade’s movement, and to prevent it from jumping out of the body.
Adjusting the Chipbreaker (Uragane)
The chipbreaker is a recent addition to the Japanese plane. In earlier centuries, they had only a single-blade. Unlike the Western Bailey-pattern planes that incorporate the chipbreaker into the linkage necessary to adjust the blade, hiraganna planes work just fine without the chipbreaker. Indeed the chipbreaker’s only role is to reduce tearout, so when tearout is not a concern, removing the chipbreaker will reduce the force necessary to motivate the plane and may even produce a smoother cut.
The chipbreaker of a new plane often needs to be fitted to the blade and body using files and stones, but that is a subject for a future article, so to keep things simple, so for now we will assume the chipbreaker is in good shape and is happily wedded and bedded to its blade.
Gentle Reader is no doubt wondering how to adjust the chipbreaker with the large head of a mallet. The answer is to use the butt of the handle as shown in the photo below. Just hold the mallet’s handle in a fist with the head upward and bring the handle’s butt down on the the chipbreaker. Easy as falling off a log, as my dear departed father would say. The connection between the mallet’s head and handle must be quite solid, of course. These mallets are easily made.
Using this technique, your plane blades will look beautiful, and your dai will give many years of reliable service. And although they only have tiny mouths with just a single, shiny, silver tooth, if you look carefully you will sometimes see their clever little smiles.
To remove or back-out the chipbreaker, one strikes the dai as if loosening the blade, but with a finger on the chipbreaker to keep it from dragging over and perhaps dulling the blade’s cutting edge.
When adjusting the chipbreaker, sometimes the blade will shift position too, so a back and forth adjustment of blade-chipbreaker-blade is sometimes necessary. The tighter the fit of the blade and chipbreaker in the body, the more fiddling is required, so craftsmen such as joiners, sashimonoshi and cabinetmakers that routinely make fine, precise cuts and sharpen frequently tend to prefer thinner blades that fit into the body with less force and are easier to adjust than do carpenters who perform less refined work.
We will delve into this aspect of handplane setup in our journey ass over teakettle down the rabbit hole in a future post.
Adjusting the Blade
In order to take a clean full-width cut, the blade must project from the mouth the appropriate amount, and evenly across its width. In other words, it must not project too far, nor too little, and one corner of the blade must not project more than the opposite corner.
To evaluate the blade’s projection through the plane’s mouth, hold the plane upside down to a light-colored uniform background and look along the plane’s sole. The correct projection will be a thin line of uniform height across the width of the sole. If one side of the blade is projecting more than the opposite side, the blade is either skewed in the body, or it is shaped skewed.
If the blade is skewed, tap the head to the right or left with the mallet. If, however, a few taps fails to make the projection uniform, the blade’s cutting edge must be reshaped.
Please be aware that continued lateral pounding on the blade will not improve the situation and may damage the wooden body.
Most planes allow a little bit of wiggle room for the blade, but sometimes, especially if the body shrinks in width due to reduced ambient humidity, the notches in the side of the mouth may need to be pared slightly deeper, or the blade ground narrower, to provide this right/left wiggle space. Be very careful, however, to avoid paring these grooves more than a thin shaving or two wider because, as mentioned above, removing wood at the grooves directly and irrevocably weakens the most tender point in the wooden body.
To test the projection of the blade, and ensure skew has been removed, hold a short, narrow piece of softwood such as pine or cedar in your hand and run it over the cutting edge, first on one side of the blade, then the opposite side, and finally the center, and observe the shavings (if any) produced. They will tell you the truth. Be careful not to shave your fingers unless they have become hairy (ツ).
Even experienced craftsmen betimes become gutted, gobsmacked, and guragura upon discovering their otherwise perfect plane blade has become skewed and is projecting too far on one side to be adjusted for a good cut without resharpening it. Of course, the culprit is almost always pernicious pixies, but a wise Beloved Customer (are there any other kind? Absolutely, totally and in all other ways inconceivable!) will be careful to follow Petruchio’s example and tame the skew. And don’t forget to use a hardened stainless steel straightedge to check the blade for square when sharpening.
Striking the Body of the Plane
Your humble servant does not want to seem repetitious, but just so there is no confusion, I feel compelled to review a point or two before we end this discussion.
When backing out or removing the blade, make it a habit to strike the chamfered edge of the dai behind the blade alternating between the right and left sides instead of dead-center.
Also, angle your strikes so they are more or less parallel to the long axis of the blade. With a little practice this will become second nature. The reason for this action is simply that it is both more effective and at the same time helps to keep the dai in one piece.
Please, never strike the flat tail end of the plane’s body flat-on, but only the chamfered top edge behind the blade. Too many people who strike the flat end of the tail get carried away and end up damaging the sole.
If you examine your plane you will notice that there is actually very little wood holding the plane’s body together in the mouth area. Indeed the only continuous wood is at the sides, and it is only as thick as the distance between the bottom of the blade grooves and the exterior sides of the body. Not a lot of meat.
If we strike the body’s tail in the center, the body, being relatively unsupported in this area, must flex creating stresses, sometimes enough to crack it, sometimes even enough to split it. This sort of damage is common, but almost entirely avoidable because, if we strike the right and left extremes of chamfered edge behind the blade, stresses will be carried through the stronger sides reducing the chances of cracking and/or splitting the tail. You can feel and even hear the difference if you pay attention.
If you don’t care how your plane looks, and prefer replacing or fixing their wooden bodies instead of using them, by all means scrupulously disregard this suggestion, in which case you might want to get some extra bubble wrap to keep yourself entertained while the bolt and epoxy repair to your plane’s broken body cures.
Damage to the body or blades of C&S Tool’s planes caused by the incorrect use of metal hammers will void the tool’s warranty.
When you purchase a plane, the blade is already installed in the body, although the cutting edge is usually recessed inside the mouth to protect it. The first step, therefore, is to remove the blade and examine it.
If you live in a low humidity area such as Nevada or Arizona in the USA and purchase a plane from a part of the world with high-humidity at times, such as Japan, it is wise to remove the blade and set the plane aside for a few days to let the body become acclimatized, especially if you plan to use the plane in a space with central heating and cooling which may cause the wooden body to shrink in width.
If you plan to store your plane for several years in a dry climate, or in a space with central heating and cooling, we recommend you remove the blade and chipbreaker, oil them, wrap them in aluminum foil, and store the body and blades together but without being installed in the body to prevent the blades from restraining the body’s shrinkage causing it to crack. Just to be safe.
In the next post in this adventure we will discuss how to modify a Japanese plane’s body to make it easier to use.
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. May my plane blade be forever skewed if I lie.
The carpenter dresses his plank, the tongue of his foreplane whistles its wild ascending lisp
Walt Whitman, “Song of Myself,” Leaves of Grass
The efficient woodworker must continue accurately cutting or shaving wood just as long as possible without stopping to sharpen his blades too frequently because time spent sharpening is time the primary job isn’t getting done. He will develop unconscious habits to help him constantly monitor the condition of his blades and the quality of the work being performed.
The Four Habits
As the saying goes, “timing is everything.”
If Beloved Customer pays attention, you will discover there is a point where a woodworking tool’s blade still cuts, but its cutting performance begins to drop off. Sensing this transition point is critical because if you continue cutting wood much past it, three things are likely to result.
The energy needed to motivate the blade will increase dramatically;
The quality of the cut will quickly deteriorate;
The time and stone expenditure necessary to resharpen the blade will increase.
That’s three variables that could be expressed in a pretty graph if one was so inclined, a graph that would have at least one inflection point. Which variable is most important to you?
Most woodworkers fail to consider these efficiency variables; They simply keep cutting away until the tool either becomes too difficult to motivate, or the results resemble canine cuisine, then stop work and resharpen the blade. But the wise woodworker will focus on minimizing the total time and total cost required to maintain his tools even if it means he must pause work to resharpen his blade well before its performance deteriorates badly.
This sharpening inflection point will vary from blade to blade and job to job because every blade, every piece of wood and and every user are unique. Simply counting strokes is not enough. It takes attention and practice to sense when a blade has reached this point.
The following are some things you should pay attention to, and habits you should develop, to help you identify the sharpening inflection point.
Habit No.1: Sense Resistance Forces: As you use a tool such as a plane, chisel, or saw, tune your senses to detect the point at which the blade becomes more difficult to motivate. As the blade dulls, the force that you must apply to the tool to keep it cutting will gradually increase. This is especially noticeable when planing and sawing. Develop the habit of paying attention to this force so you can determine when it is time to resharpen.
Your humble servant recommends you regularly use an oilpot to ensure any increased resistance is actually due to a dulled blade and not just increased friction between the tool and the wood (or pixie predations (ツ)).
Habit No.2: Listen to the Music: Pay attention to the tool’s song. That’s right, turn off the radio and CD player, shush that jabbering little 3 year old rolling around in plane shavings under your bench, and listen to the music your blades make instead. If you do, you will notice that each tool sings its own song, one that varies with the wood, the cut, and the condition of the blade. Is the blade singing, lisping, or croaking as it chews wood? Is it a saw with a basso profundo voice, or a mortise chisel with vibrant tenor tones, or perhaps a soprano finishing plane singing a woody aria? A sharp blade makes a clearer, happier sound when cutting or shaving wood than a dull one does. Learn the bright song it sings when it’s sharp and the sad noise it makes when it’s dull, and all the tones in between. If you have ears to hear, it will tell you what kind of job it is doing and when the time has come to resharpen it.
Habit No.3: Eyeball Cuts: Watch the tool and the wood it has cut. Is your chisel cutting cleanly, or is it crushing the wood cells? A sharp chisel blade cuts cleaner than a dull one. You can feel and hear the difference. And you can see the difference in both the shavings or chips and the surfaces the tool leaves behind. Don’t be a wood butcher: develop the habit of frequently checking the quality of your cuts. It doesn’t take extra time, and your tools will wiggle with happiness at the attention you give their efforts.
Habit No. 4: Feel the Surface of the Wood:Is your plane shaving the wood cleanly, or are the surfaces it leaves behind rough with tearout? Develop the habit of running your fingertips along the path your plane just cut to sense surface quality. If you detect roughness or tearout, the plane may be out of adjustment, or more likely, the blade is becoming dull. Or maybe you need to skew the blade, change the direction of the cut, or moisten the wood’s surface with a rag dampened with planing fluid (I use either water, industrial-grade busthead whiskey, or unicorn wee wee when I can get it).
Next, run your fingertips across the cut your plane just made to detect ridges that may have been created by irregularities or chips in your blade’s cutting edge. Every one of those ridges indicates a small waste of your time and energy and a flaw created in the wood. Don’t forget that the tops of those ridges contain compressed cells (kigoroshi) that may swell and become even more pronounced with time. These tasks are easily accomplished in passing with a few swipes of the fingertips along and across the wood between cuts without spending any extra time.
These techniques are not rocket surgery. They don’t take extra time. They can be applied to any tool all the time. The key is to pay attention; To listen to one’s tools; To watch their work.
Let’s next shift our attention to three of the Mysteries of Woodworking, their potential impacts on mental health, and how to avoid unfortunate wardrobe decisions.
The Mystery of the Tilting Board
To discuss this Mystery, we will call on the services of my old buddy Richard W. (Woody) Woodward. You may remember him from a mystery story in a previous article. Yes, it was a near thing, but he has fully recovered from alcohol poisoning after chugging a 5th of tequila in an emotionally-charged bout of drama over a brittle blade.
Anyway, this mystery goes something like this. Woody is planing a board about the same width as his plane’s blade down to a specific thickness, but for some unfathomable reason, the board ends up thinner on one side of its width than the other. He checks the blade’s projection from the plane’s mouth, but it is absolutely uniform. In fact to plane the board to the correct thickness he ends up having to tilt the blade to take less of a cut on one side of the board than the other.
Most everyone has experienced this curious and wasteful phenomenon, but because it is not consistent, many never solve the mystery of the tilting board, blaming it on Murphy’s ministrations or pixie perfidiousness. But never fear, because the solution is elementary, Dear Watson.
In Habit No.4 listed above, your humble servant mentioned residual “ridges.” Please be aware that these ridges are not only unsightly and may damage applied finishes later, but they can actually keep your plane from cutting shavings of uniform thickness. Think about it.
Let’s assume you are planing a board the same width as your plane blade, but the blade has a tiny chip near the right end of the blade that leaves behind a .0005″ high ridge on the board’s surface. With each subsequent cut using this same blade with the same defect the right side of the plane’s body and likewise its blade will be elevated above the board’s surface by .0005″, while the left hand side, which doesn’t have any ridges for the plane’s sole to ride on, is shaved the normal amount. The difference in the amount of wood shaved from the right and left sides with each individual cut is minute, of course, but it accumulates with each pass sure as eggses is eggses
Assuming you checked that the blade is projecting from the plane’s mouth the same distance across its entire width, with each pass the surface of the board becomes tilted, a little high on the right side and a little low on the left, so that instead of a flat surface square to the board’s sides, you have produced a flat surface that is thinner on the left side and thicker on the right. Muy malo, amigo.
If, while performing the checks listed above, you detect ridges on a freshly-planed surface, immediately check the blade’s cutting edge by running a fingernail along it’s width. Don’t worry, it won’t dull the blade unless you are also a bricklayer. Your nail will feel the catch and grab of defects too small for your eye to see. A few small ones may make no difference, but on the other hand, they might make a big difference.
Often these ridges will show up as lines of thicker wood in your plane shavings. You do occasionally examine your shavings, right?
With this, the Mystery of the Tilting Board, one that has driven many a woodworker to distraction, too often leading to regrettable fashion decisions involving stiff, canvas jackets with long sleeves connected to straps and buckles that fasten behind the barking woodworker’s back and even pass under the crotch (decidedly uncomfortable, I assure you), has been solved. Rest assured, only the Beloved Customers and Gentle Readers of the C&S Tools Blog can be certain of avoiding this undignified state of dress.
The Mystery of the Missing Plan
Here is another mystery of woodworking, one that especially vexes those tender souls new to the calorie-burning fun of dimensioning boards by hand.
Let’s say Woody needs to turn a bunch of twisty, banana-shaped boards into flat, square, precisely dimensioned and cleanly-surfaced drawer fronts to make 24 piston-fit drawers. Let’s also assume the wood he uses for each drawer-front is unique in both appearance and warpage. It’s a heck of a lot of wood to cut with no time to waste, so our erstwhile wood butcher gets out his trusty handplane, sharpens it up, adjusts the blade and chipbreaker, gives it a kiss for luck, and send wood shavings fly through the air with gleeful abandon!
But wait just one frikin minute! No matter how much Woody planes, he just can’t seem to make some of the surfaces flat, free of wind and the sides square to the faces. It’s like some kinda moving target! Indeed, eventually he is dismayed to discover some of the board’s edges are getting too thin. What to do, what to do!?
Drama queens like dear Woody typically begin interesting antics at this point, but not so our Beloved Customers who, unlike Woody, are stoic, laconic, intelligent and of course, sharply-dressed, and therefore pause their physical efforts to focus their mental powers on solving this mystery.
At this point the resident benchdog may perk up his ears, tucks in his tail and beetle away in fear of the smoke and humming sound emanating from BC’s ears; Master Benchcat arches his backs, hisses like a goose, and flees the workshop as if his tail is on fire; And the resident pixies frantically hide in the lumberpile to avoid being disrupted by the power they sense radiating from BC’s mighty brain!
Of course, the culprit is operator error.
Don’t forget to clean up the cat urine because it’s toxic to tools.
Too few people really pay attention when using their tools, focusing like a badger after a squirrel on making as many chips or shavings as quickly as possible without a plan. For example, a failure common to many woodworkers is to start planing without first identifying and marking the high spots that must be cut down first, and then areas to be cut down next. In other words, they fail to plan the sequence of the work. The result is that time, steel and sweat is wasted cutting wood that didn’t need to be cut while ignoring wood that should have been cut first. And all for lack of a plan measured with a straightedge or dryline and marked on the board with a few strokes or circles of a lumber crayon or carpenter pencil
This mystery too has been known to increase profits of the mental health industry and even (heaven forfend!) fashion decisions involving poorly-tailored canvas jackets with crotch straps. Simply not to be borne!
Remember, when the goal is to make a board flat efficiently, always begin the job by identifying high spots and low spots and marking them. Then, always begin by planing down the high spots while avoiding the low spots. One mystery solved!
The Mystery of the Sounding Board
Lastly, we come to perhaps the most frustrating and least-understood of the Mysteries of Woodworking. Not to say there are no other mysteries, because there is always that most ancient of riddles that baffled even the enigmatic Sphinx, one which has tortured men since before Pharaoh wore papyrus nappies, namely that of honestly answering one’s wife when she asks him if her new pair of jeans makes her bottom look “simply humongous.” Sadly, this is one mystery upon which your humble servant is unable to shed light because even I “never could find no sign on a woman’s heart.”
But I digress. This Mystery is one that torments those badly befuddled souls like friend Woody who, lacking a plan to follow, eyes that see, hands that feel and ears that hear, unwisely assume the board they are planing is stable simply because it doesn’t walk away. Perhaps it is the malevolent influence of pernicious pixies that causes him to ignore that the downward deflection the pressure of the plane unavoidably induces in a warped, unevenly supported board, or in a board being planed on a flimsy or crooked workbench.
This unintentional, indeed unnoticed deflection too often causes the board to escape the cutting blade resulting in hills being raised and valleys remaining low where flat surfaces were required. Of course, this leaves the handplane bitterly dissatisfied.
But this waste of wood, steel, sweat and goodwill can be avoided because, even if the board isn’t rocking like Zepplin and dear Woody can’t feel the board deflecting away from his plane’s cutting edge, he could detect the change in his plane’s song when it is cutting an unsupported area of a board if he only listened because the piece of wood he is shaping is also a “sounding board.”
Think of all the money saved that Woody would otherwise spend on lithium, Prozac, and small hotel rooms with padded walls to ease his mental anguish if only he had the foresight to make a plan, train his hands and eyes to confirm his tool’s performance, and his ears to listen to what his plane tries to tell him.
Here is wisdom: The experienced professional will investigate each board, make a plan for his work, mark the plan on the wood, shim the board so it is evenly supported on a flat workbench surface, and sharpen his blade if necessary before making a single cut. Then instead of cutting randomly like a paintbrush-wielding modern monkey artiste, he will make each cut intentionally, purposefully, in accordance with his plan to make the work go as efficiently as possible.
He will also pay attention to the reaction of the wood and feedback from his tools during each cut. He will use the four habits discussed above, and maybe even a drop or two of unicorn wee wee to limit tearout if his budget allows.
If Beloved Customer doesn’t have a master to give you a dirty look or to box your ears when you impatiently err, you must train yourself. Slow down. Make a plan. Execute the plan. Pay attention, use your senses, and spend the time needed to evaluate progress against the plan. Consider carefully why the work is going well or why it is not.
This process will slow the work down at first, but over time it will sharpen your instincts, tune your senses, and help you develop good habits that eventually accelerate your work while improving the quality of the end product.
It will guide you along the path to becoming a master craftsman.
May the gods of handsaws smile upon you always.
Until we meet again, I have the honor to remain,
If you have questions or would like to learn more about our tools, please click the see the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may my straight-jacket straps dig infected furrows into my crotch.
There are few blessings without a curse hidden inside, nor curses without a whiff of blessing. Like most things, it’s a matter of how you look at it.
Joe Abercrombie, Isern, “A Little Hatred”
In this article your humble servant will attempt to shed more light on the ancient “Mystery of Steel.”
This story does not begin on a dark Scottish moor, nor on a foggy London night in a drawing room with the door inexplicably locked from the inside concealing bloody mayhem splattered across intricately carved linenfold oak paneling; Rather, it begins in an ordinary woodworking shop. And it goes something like this.
The Brittle Edge
The curtain rises on a humble detached workshop where, unbeknownst to our victim, an erstwhile woodworker we shall call “Woody,” dastardly events are about to unfold (cue the deep, ominous music). It’s really just an old dilapidated garage, but it’s Woody’s kingdom and he is master here, or so his bench cat allows him to imagine. He’s expecting us, so we’ll just go on in.
Make sure the door is firmly closed behind you now; It tends to stick and Woody’s bench dog loves to jet out and root around in the neighbor’s garbage. No mystery about why they call the fuzzy little leg-humper “Stinky.” (ツ)
Pine and cedar plane shavings litter the floor of Woody’s shop and their fragrant aroma fills the air erasing the mutt funk. Autumn sunlight filters gently through the single dusty window as sawdust motes dance above a limp bench cat sleeping at the far end of the workbench dreaming of buffalo wings and big-eyed kittens. All appears well in Woody World.
Woody’s sitting at his workbench on his white Smith & Wesson padded stool where he has just unpacked his new chisel, admired it, checked the fit, finish and edge, and appears quite satisfied. He lays out a test mortise hole on a piece of scrap oak, picks up his gennou hammer (the one with the classic Kosaburo head and the sexy Osage Orange handle that turned out so well), and begins to chop a test mortise. But, wait!… Something’s not right!
With trembling hands, Woody examines the chisel’s cutting edge to discover the last thousandth of an inch or so has changed from smooth and sharp to ragged and dull. “Nooooo!” Woody wails as he lifts his arms to the ceiling, arches his back, and slumps to the floor on his knees in a pose reminiscent of Sergent Elias in that poignant moment on a battlefield in Vietnam; “I have been betrayed!” he cries with wavering voice. Yes, Woody’s a talented and enthusiastic drama queen in the Smeagle mold; Maybe even good enough to run for the US Congress.
Another of Woody’s qualifications for high public office is that he dearly loves to pull a cork, so while he walks to the corner Piggly Wiggly to get a 5th of tequila to anesthetize his emotional shock and refill his thespian fuel tanks, let’s take a load off and sit on his workshop sofa over there while I explain the cause of his emotional fragility. Yep, you’re right; It’s a recycled bench seat from an old Dodge Power Wagon he salvaged from a junkyard and converted to a sofa for watching ballgames and taking naps in the shop away from the jaundiced eye of “She Who Must Be Obeyed.” Don’t worry about your pretty pink dress, princess, it’s just honest sawdust.
With tools, tequila, and the mystery of steel involved, this could be a long story, so let’s consider how to solve this particular mystery before Woody gets back and starts up his caterwauling again.
But just so you don’t become discouraged, let me state right now that there is a tunnel at the end of the light, and that while all seems dark and hopeless to Woody now, he may actually have reason to rejoice greatly! But we’ll get back to that later in the story.
Your humble servant always asks the following questions when someone complains of a chipped cutting edge on a chisel or plane. When Woody gets back, and if he manages to remain coherent and vertical long enough, we’ll ask him these same questions. If your blades are causing you grief, you should consider asking yourself these questions too. Jose Cuervo and acting skills are not required.
What sort of quality is your problem chisel? Low? Medium? High? How do you know? This is relevant because a poor-quality chisel will fail just by looking at it too hard;
What type of chisel is it? A striking chisel or a paring chisel? Each type of chisel is used for different tasks and in different ways;
What and how were you cutting when the edge failed? This is important because some woods are best cut in a different manner than others, and some cuts require a special approach if we are to avoid damaging the chisel;
What is the bevel angle? If the angle is much less than the ideal for the type of chisel, plane, cut and wood, we may have found the culprit. Finding the perfect angle for your chisel and situation may take some experimentation;
How did the edge fail? Did it crumble? Chip? Roll? A combo failure (with cheese)? This will tell us a lot about the tool.
Was the wood you were cutting dirty? Did it contain embedded grit? This is an important question because many people carelessly use their valuable chisels, planes and powertools to cut hard minerals instead of scrumptious wood. The lesson? Don’t be a slob: Scrub your wood with a steel brush before cutting it. And saw off the last 3~4 millimeters off both ends of every board, or at least chamfer the ends with a block plane, drawknife or knife to remove the grit always embedded in end grain, before you put it through your jointer, thickness planner or tablesaw, or cut it with handsaws, planes or chisel. If you have not made a habit of doing this, don your scratchy sackcloth tidy whities, smear ashes on your face, then repent and be baptized because you have been abusing your innocent tools, Bubba. Clean your wood and you will notice the difference. Strange that no one I have ever asked this question to has admitted to using dirty, stony wood at first. The reason is usually simply that they didn’t realize it was filthy until I pointed it out to them, just as it was pointed out to me many years ago. What’s that you say? You don’t have a stiff steel wire brush in your toolbox?! Shame on you;
Did you abuse the chisel by trying to lever wood out of the cut, a mortise for instance? This is a common cause of failure. People accustomed to using amateur-grade tools with soft cutting edges frequently discover the edge of their new chisel has chipped after using it like a cheap Chinese screwdriver to lever waste, never imagining the harder and more brittle steel of a quality chisel might be damaged. Such boorish behavior voids the warranty on our chisels, BTW, because a chisel is a cutting tool, not a prybar, can opener, or paint stirrer, much less a screwdriver.
Did your answers to these questions suggest any remedial action to you? The best answer to Question 1 is often to procure a better-performing tool.
But if your tool is professional-grade instead of hardware-store grade, then you may need to learn how to use it and maintain it properly. But that is a story for another day.
Let us shift our attention briefly to another, related mystery, one that has more to do with human nature.
Why Are the Blades of So Many Modern Tools Mediocre Performers?
It wasn’t always that way, but there are sound business reasons why chisel and plane blades are such poor performers nowadays, even in Japan, and like many things, it boils down to money. The numbers of craftsmen that routinely use handtools has decreased, and therefore the demand for professional-grade tools is way down. In Western countries the degradation of tool standards started even earlier.
In this situation, and where customer expectations are as high as an earthworm’s vest pocket, mediocre tools are simply more profitable for manufacturers and retailers. After all, low-quality materials are cheaper and it only takes ordinary machines and minimum-wage factory workers, not expensive trained blacksmiths, to make tool-shaped objects from mediocre-quality materials. Professional woodworkers won’t touch such crap, but amateurs, the inexperienced and those bewildered souls who judge performance based solely on lowest cost buy them by the ton.
More now than ever, “sustainability” is given pious, pompous lip-service, while the reality of modern society is that high-volume sales of colorful but poor-quality tools designed to meet planned obsolescence goals, manufactured in lots of thousands by Chinese farmers, and destined to become early landfill stuffing has become the only viable business model left standing. Gofigga.
More importantly, even if they would do better if given half a chance, inexperienced amateurs seldom have anyone to teach them how to use and maintain their tools, so they never learn proper maintenance principles and cutting techniques. When they damage their woodworking tool blades carelessly, they blame the tool supplier for their own failure. As Mr. T would say: “I pity the fool.”
Faced with this sort of consumer, it is simply easier and more profitable for tool companies to manufacture, and for retailers to sell, chisels and planes with softer, tougher blades suited to amateurs. I think you can see the vicious cycle.
A Non-technical Technical Explanation
Your humble servant’s earlier comment that Woody may have cause to rejoice about what appears to be metallurgical malfeasance may cause some Gentle Readers to wonder if I am mad as a sack of owls; Perhaps my most excellent aluminum-foil skull cap (the one with purty curly copper wires) malfunctioned permitting those icky inter-dimensional aliens’ mind-control waves to leak through.
Like our absent drama queen, I too was devastated when first faced with a manifestation of the Mystery of the Brittle Blade many years ago, but I can now explain why it may be sign of a blessing instead of a curse. It’s elementary dear Watson. But I think it best to provide some background and explain some time proven solutions before presenting the good news. Steak before ice-cream, you see.
I beg the indulgence of knowledgeable Gentle Readers who feel insulted by the lack of temperature curve drawings and jargon such as “pearlite,” “martensite” and “ austentite,” and ask them to understand that, while this blog is focused primarily on informing our professional Beloved Customers, many Gentle Readers require a less technical explanation. Simple hospitality demands that your humble servant make an effort to provide useful insight to a wide range of Gentle Readers. As a dude wearing a skirt and sandals in a movie once said: “ Are you not entertained?”
Quenching the Blade
When a blacksmith quenches a high-carbon steel blade in water in the ancient manner (called “Yakiire” 焼き入れ in Japanese which translates to “burn in” in English), the steel suffers a thermal shock, sometimes severe enough to crack it. This violent cooling also causes a peculiar crystalline structure to form in the metal, one that causes it to become harder and increase in volume, and even to warp to some degree. The casual observer may imagine the water cools the entire blade uniformly, but ‘tain’t so.
Those areas of the blade that cool the quickest form the highest volume of crystals and become hardest. In the case of chisels, planes, and kiridashi knives, the end of the blade has the most exposure to water, cools quickest, and therefore becomes hardest, at least during the first quench.
The blacksmith may carefully repeat the heating and quenching process multiple times, sometimes varying the heat time and temperature to achieve the desired crystalline structure and uniform distribution of small, hard carbides that define “fine-grained steel,” but the quenching process by itself always leaves the blade too hard and too brittle to be useful as-is.
Tempering the Blade
Now that the blade is hardened, indeed too hard, the blacksmith must mellow the steel, reducing its hardness while at the same time increasing its toughness by carefully reheating and cooling the steel to modify the crystallized steel in a process called “tempering,” in English and “yakimodoshi “ 焼戻し ( literally “ burn return” ) in Japanese. In this way, a steel blade hardened to Rc85 degrees during the first quench, indeed brittle enough to break into pieces if dropped onto a concrete floor, can be softened to a useful hardness while becoming at the same time much tougher.
In materials science and metallurgy, toughness is defined as the ability of a material to absorb energy and elastically deform without fracturing. To “elastically deform” means an object changes shape or deforms when pressure is applied, but returns to its original shape when the pressure is removed. For example, if you clamp one end of a piece of mild-steel wire in a vise and apply a little force with your hand at the other end it will bend at first and then spring back to its original shape when you remove pressure. This is called “elastic deformation.” But if you apply enough pressure the wire will not spring back (“rebound”) but will remain bent. This permanent bend is called “plastic deformation.” Mild steel wire is truly “tough as nails.”
Glass is the opposite case. While it exhibits more elastic deformation than most people realize it can, it will tolerate no plastic deformation, because when the stresses in glass reach the “yield point,” instead of bending plastically, it breaks.
A brittle blade is hard but not tough, and while it will elastically deform a little bit (often so little it’s unnoticeable), it too easily breaks. Proper tempering therefore, is critical to obtain useful toughness.
But this reduction in hardness and increase in toughness brought about through tempering is not always 100% uniform, and as mentioned above, the extreme cutting edge of the blade of a chisel or plane tends to be hardest and therefore most brittle in the case of hand-forged tools, even after tempering. The cheap, mass-production solution is to simply make the entire blade softer, say Rc55 for example, so brittleness will never be a problem. But such a tool is more a sharpened screwdriver than a cutting tool suited to the needs of professional woodworkers, IMHO.
I’m being too harsh, you say? Not even a little bit. A soft blade dulls quickly, wastes the professional woodworker’s time and money, and is irritating instead of useful. Perfect for turning screws, spreading spackle or stirring paint but not much good for quickly and precisely cutting lots of wood for pay, thank you very much.
Solutions 1 & 2
The Mystery we are investigating on Woody’s behalf is as ancient as steel itself. And of course there are reliable ancient solutions our blacksmiths employ. Let’s consider two of them.
First, create a crystalline structure in the blade through hand-forging that is more resistant to fracturing than ordinary steel regardless of its hardness. This doesn’t happen by accident.
Second, employ painstaking heat-treatment techniques combined with uncompromising quality control to achieve the right balance of hardness vs. toughness.
To help control the heat-treat process, our blacksmiths apply a special mud-like compound to specific areas of the blade to slow down the thermal shock during the quench and improve the steel’s crystalline structure. Every blacksmith has their own “secret sauce,” so I can’t tell you what it’s made from. This technique is not perfect nor unique to Japan, but we know it has been successfully used by Japanese swordsmiths for at least 900+ years
It ain’t rocket surgery, but factory workers in Guangzhou or Mumbai can’t do it.
So, we have discussed the reasons, and some solutions, but what to do about a blade that’s already chippy?
Assuming the blade has been forged by an expert blacksmith in accordance with the principles outlined above, the fix to chippiness (oops, did I coin a word?) is to be patient and sharpen the blade three or four times removing the extra-brittle steel exposed at the cutting edge, the area that became harder and less tough than the rest of the blade during the heat-treating process. With few exceptions, the blade will then “calm down” and stop misbehaving.
This is the solution we ask our Beloved Customers to employ when this problem infrequently arises. It requires faith, and patience, but it almost always works.
The last solution, and one I certainly do not recommend to anyone except as a last resort, is to heat the cutting edge under a candle flame. Not an acetylene torch; Not a propane torch; Not even a butane lighter; A candle flame only. You want the extreme cutting edge to become just a smidge hotter than you can comfortably touch with your bare finger. Don’t heat the entire blade, just the cutting edge.
BIG FRIKIN DISCLAIMER 1: This method won’t fix a poor-quality blade or one that was initially ruined during forging or heat-treat.
BIG FRIKIN DISCLAIMER 2: If you are careless and do this wrong you can easily ruin the blade!
But what insanity made me say that Woody should rejoice when the cutting edge of his new chisel crumbles? I assure you, my reasoning is sound, I have Woody’s best interests at heart, and I will explain all to him when he sobers up. Probably tomorrow afternoon, at this rate. (ツ)
But I’ll explain it to you now, if you will be good enough to get me a root beer to wet my whistle from Woody’s cooler over there. No, that’s not a Class M-3 Model B-9 General Utility Non-Theorizing Environmental Control Robot, it’s one of those mini-fridges sitting on two skateboards with a shop-vac wrapped in Christmas lights perched on top that Woody puts out on his front porch for Halloween to thrill the kids and to keep a sufficient stash of cold adult beverages, and root beer too, of course, close at hand. He’s very practical that way. Oh, BTW, please don’t tell SWMBO about the adult beverages, or you’ll ruin a great Halloween tradition and preclude many erudite discussions in the future: Vino Veritas
Ahh, that’s better. Nothing like an ice-cold root beer.
Now where was I? Oh yes, the reason for my optimism: A high-quality blade that crumbles like Woody’s did when brand new, and mellows after a few sharpenings, is highly likely to be an exceptionally fine tool!
On the other hand, a blade that is too soft when new will never crumble or chip, but it will always quickly dull and never improve. A veritable gasket scraper. (个_个)
There are exceptions, of course: some hand-forged blades are defective and crumbly from beginning to end, usually a result of overheating the steel during the forging process, a rookie mistake. You should return such a defective blade to the retailer you purchased it from. If, however, to save a few bucks, you rolled the dice and bought a tool without a warranty, or purchased it from an online auction, you will need to enlist the services of Murphy’s two bubbly buddies Mr. Doodly and Mr. Squat.
Somehow I doubt Woody will thank me for solving this piece of the Mystery of Steel for him, but I am confident he will love the flavor of that chisel for the rest of his life.
PS: If you found this interesting, you may find other posts regarding the Mystery of Steel found in our “Sharpening Series” interesting too. The one at this link in particular is relevant to this discussion.
If you have questions or would like to learn more about our tools, please click the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.
Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. May I gag on a hairball if I lie.
It is well with me only when I have a chisel in my hand
This is the first in a five-part series about the Mortise Chisel, especially the Japanese version.
Also called the “Joiner’s Chisel” in Japan, this is a specialized chisel used by specialist craftsmen to cut precise, smallish joints when making furniture, cabinetry and joinery. Carpenters don’t use it, and few have in that august trade have even seen one.
In this post your humble servant will introduce a tiny bit of the terribly long history of the mortise and tenon joint, and give a description of this specialized chisel.
In future posts we will look at how to evaluate, adjust and even how to use the Mortise Chisel in general and the Japanese Mortise Chisel in particular. We will also touch on bevel angles and blade hardness problems.
We will discuss what to look for in a good mortise chisel and how to examine it with an eye to increasing its performance. This is something most users of chisels never consider, but it can make a big difference in the case of mortise chisels. Indeed, I daresay most Gentle Readers will mutter the equivalent of “Bless us and splash us” when they read it.
Of course we will also discuss how to effectively correct irregularities in our mortise chisel that negatively impact performance, irregularities most people never notice.
After our Mortise Chisel is properly fettled (they almost always have some problems) we will take our racing chisel out for a few laps, but prior to that we will consider how to effectively use this specialized tool. Too few receive proper training nowadays in chisel work, but here are C&S Tools we feel it our duty to help our Beloved Customers improve their skills.
We will conclude this series by taking the “Old Master’s Test,” just to make sure both our Mortise Chisel and our skills are improving.
While focused on the Japanese Mortise Chisel, the principles and improvements discussed in this series of articles are applicable to any chisel used to cut mortises.
While all Gentle Readers with eyes to see, ears to hear, and hands that love wood are welcome to share this hard-earned knowledge, it is intended primarily for our Beloved Customers, especially those who use chisels professionally to keep body and soul in close proximity.
Your humble servant drafted this series of posts years ago, and has shared bits of it with Beloved Customers from time to time when requested, but the information has not always been well-received for a number of reasons.
There is an old Japanese saying, one which probably originated in China, written 「馬の耳に念仏」and pronounced “Uma no mimi ni nenbutsu,” which translates to “Prayers in a horse’s ear.” Why are Buddhist prayers relevant you ask? Good question. You see, some of the principles I will present in this series directly contradict doctrine taught by some of the Holy Woodworking Gurus in the West. Like vespers to a beast of burden, wisdom is wasted on the willfully, woefully ignorant (wow, that almost sounds like iambic pentameter!).
But our Beloved Customers are neither horses nor asses nor politicians but shockingly intelligent human beings to whom your humble servant is convinced the time has come to expound the gospel of the Mortise Chisel as it was taught to me by Masters who have since abandoned this impure world for more ethereal realms.
This series of posts is equivalent to a graduate school course in chisels, something like “Mortise Chisels 701.” And just like a course in advanced differential equations, most Gentle Readers will never need it. But never let it be said that your humble servant didn’t do his best to improve both the skills and the tools of our Beloved Customers.
Some History of the Mortise & Tenon Joint
Mortise chisels are used for cutting rectangular holes in wood usually intended to accept tenons to form a structural connection called the “mortise and tenon joint” between pieces of wood.
No one knows how long humans have been using the mortise and tenon joint, but it has certainly been longer than nails, and many thousands of years longer than screws, although modern humans with their lithium battery-powered, made in China, landfill-bound, multicolored plastic and rubber screwdrivers may find it difficult to imagine. So let’s begin the journey by briefly examining just two well-documented extant physical examples that may provide motivation for using this enduring joint.
The oldest known wooden structure is a neolithic well liner discovered near Leipzig Germany, constructed from oak timbers shaped by stone adze and joined at the corners with half-lap joints and pinned tusk-tenons at through mortises. Tests indicate the trees the timbers were split from were felled between the years 5206 and 5098 BC, making the assembly at least 7200 years old.
Next, let’s look at a less soggy but more recent, complicated and elegant example.
The oldest existing wooden building in the world is a Buddhist Temple named Horyuji located in Nara Japan. Originally constructed around 600 A.D. and rebuilt around 700 A.D. after a fire, this huge 1300 year-old temple and pagoda complex was reconstructed using hundreds of thousands of hand-cut mortise and tenon joints, testifying to the longevity of wooden structural systems and the value of this universal connection technique.
Horyuji is far more than just a temple to Buddhism, it is a temple to woodworking. If you haven’t yet visited it, you’re truly missing something.
I mention these two examples to illustrate the universality, strength, and durability of the mortise and tenon joint. Anyone serious about woodworking must master this most ancient and essential connection.
The mortise chisel is the best handtool for the job of cutting mortises less than 15mm in width. For wider mortises, well-fettled oiirenomi or atsunomi are more efficient.
Japanese Mortise Chisels
In the Japanese language mortise chisels are called “mukomachi nomi” (向待鑿), with “nomi” meaning “chisel.” Don’t ask me the origin of the rest of the word because I don’t have a clue, and have heard few plausible explanations. There is another post linked to here that contains more information about this chisel.
I will use the term mortise chisel in this article to refer to mukomachi nomi.
For our Gentle Readers interested in the Japanese language, there are several combinations of Chinese characters used to write mukomachi, none of which make much sense or seem related in any way to either tools or woodworking. The most common characters used are “向待” with the first character meaning “there” or “direction,” and the second character meaning “wait.” Combined, they seem to mean “Waiting over there,” or something like that.
I assume the name was originally phonetic and somebody decided to use these kanji because their pronunciation matched the phonetic name. This sort of linguistic contortion is seen frequently in Japan, and has been a source of confusion for all and sundry for many centuries. I blame it on elitist Buddhist priests going back and forth between Japan and China over the centuries, but it is typical of the Japanese people in general and priests in particular to take a perverse pleasure in intentionally making and using terms others can’t figure out.
This confusing practice is not unique to bald priests. When I was an engineering student, I recall the professors insisting we never attempt to simplify or too clearly explain the technical jargon of the trade to non-professionals because it was essential to job security for them to never quite understand it.
If you are familiar with Japanese architecture, you have seen the wooden lattice work that defines it in doors, windows, dividers, shoji, fusuma, koshido, glass doors, ceilings, and even fences, all items made by “tategushi” or “joiners” in Japan. Each piece of any lattice needs two tenons and two matching mortises to stay in-place, so a single piece of traditional Japanese joinery may have literally hundreds of small, very precise mortises, indeed thousands in the more complicated pieces. The Japanese mortise chisel was developed specifically at the request of joiners for this type of work. Therefore, it is also known as the “Tategu Nomi” which translates to “joinery chisel.” Few carpenters use this chisel.
Japanese mortise chisels are similar to other Japanese chisels in having a laminated steel structure with a hollow-ground ura (flat), an integral tang, wooden handle, and steel ferrule and hoop. Unlike most other chisels it has a rectangular cross-section with sides usually oriented 90˚square to the hollow-ground ura, and either flat or just slightly hollow-ground to better keep the blade aligned in the cut and to dimension and smooth the mortise’s walls.
Western mortise chisels do not typically share this detail, although unusually intelligent and observant Western woodworkers of course modify their chisels to gain similar benefits.
If speed and precision are important to you, then the sides of the chisel being oriented at 90° to the ura absolutely provide a serious advantage when cutting most mortises because the sides, and especially the two sharpish corners where these three planes meet, will effectively shave and precisely dimension the mortise’s side walls as the mortise is being cut without the need to pare them later.
Unlike most mortise joints cut with oiirenomi or atsunomi, so long as the mortise is the same width as the mortise chisel, and the user has the ability to maintain the chisel at the right angle while striking it with a hammer, the width of mortises cut with this chisel are usually quite precise and seldom if ever need be cleaned with a paring chisel. This functionality means that you can cut mortises, and especially small ones, both precisely and quickly with great confidence. It’s not called the “joiner’s chisel” for nothing.
The mukomachi chisel does not work as well in wider widths because of the increased friction between the chisel’s sides and the mortise’s walls. For joints wider than 15mm, please use a trued oiirenomi or atsunomi. And don’t forget to use your oilpot.
In the next class in our graduate course on the care and feeding of the wild mortise chisel, we will examine the various details to look for in an effective mukomachi nomi. Most of these details are applicable in the case of other chisels such as oiirenomi and atsunomi too, indeed any chisel intended to be used to cut mortises including Western mortise chisels.
But wait a minute! Before ya’ll run out of the classroom like a caravan of crazy stoats chasing a pixie, please pick up your homework assignments from the table by the exit doors. And please, don’t leave your empties behind on the floor. Paper coffee cups are one thing, but diascarded aluminum beer cans attract out-of-work divorce lawyers and other such desperate vermin.
See you next time.
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Other Articles in “The Care and Feeding of the Wild Mortise Chisel” Series
The things that will destroy America are prosperity-at-any-price, peace-at-any-price, safety-first instead of duty-first, the love of soft living, and the get-rich-quick theory of life.
The terms White Steel and Blue Steel frequently pop up in discussions about Japanese woodworking tools and kitchen knives. The usual misunderstandings abound in those discussions and BS takes majestic wing.
In this article your humble unworthy servant will try to share some accurate information sourced directly from the steel manufacturer, ancient blacksmiths that actually work these steels, and Japanese professional craftsmen paid to make sawdust and shavings using these steels instead of the usual soft-handed shopkeepers and self-proclaimed experts pontificating from their Mom’s basement.
We will begin by studying some etymology of two of Japan’s most famous modern tool steels. We will then drop into history class to discuss ancient domestic Japanese steel, and then shift our attention to why these modern steels came into being. After that, we will go to metallurgy class, but without most of the technical jargon, to understand what chemicals these steels contain and why. We will also outline the defining performance characteristics of those same two steels in the case of woodworking tools.
For those who enjoy more technical details combined with pretty pictures, we have concluded with the results of a brief but very informative materials engineering study.
There’s much work to be done, so please stretch your muscles and ready your BS shovel.
Product Designations: Yellow, White & Blue and Label Steels
These terms refer to tool steels manufactured by Hitachi Metals, Ltd. (HML) in their plant located in Yasugi City in Shimane Prefecture, Japan. If you are into woodworking tools or Japanese cutlery you have probably heard of them.
Hitachi, Ltd., founded in 1910, is one of Japan’s largest and most prestigious manufacturers. Its subsidiary, Hitachi Metals, Ltd., was established in 1956 primarily through acquisitions.
“White Steel” is an abbreviated translation of HML’s nomenclature of “Shirogamiko” 白紙鋼, which directly translates to “White Paper Steel.” Likewise, “Blue Steel” is an abbreviation of “Blue Paper Steel,” the translation of “Aogamiko” 青紙鋼.
Just as “Johnnie Walker Blue” is the product name of a Scottish whiskey with a blue label pasted onto the bottle, Aogami is the designation of a particular formulation of high-carbon tool steel with a blue-colored paper label pasted onto it by the steel mill. It’s that simple.
While Johnny Walker may be kind sorta yellow in hue, it is definitely not tinted blue anymore than JW Red Label is sangre. Likewise, the color of Hitachi Metal’s tool steels do not vary in color, only their labels do. BTW, if someone tells you they can tell the difference between these steels by simply looking at them, tell them to give you a nickle and pull the other one for some fragrant, musical entertainment
There are those who insist they can tell the difference between steels by licking them. Our feline masters see this as further evidence that some humans are just not right in the head.
Since your humble servant can read and write Japanese, I feel foolish calling these materials White Steel or Blue Steel as many in English-speaking countries do, so prefer to call them Yellow Label Steel, White Label Steel or Blue Label Steel in English, or Kigami, Aogami, or Shirogami steel. Please excuse this affectation.
Now that adult beverage nomenclature, greenhouse gases and feline psychoanalyses is out of the way, let’s go back in time a few hundred years. My tardis is that blue box just over there. A change into period-correct wardrobe will not be necessary, but please put away your iPhone and try to not embarrass me in front of the locals by holding it over your head and wailing “There’s no signal!!” if you will be so kind.
Traditional Japanese Steel: Tamahagane
Tamahagane, written 玉鋼 in Chinese characters, which translates to “Jewel Steel” and is pronounced tah/mah/hah/gah/neh, is famous as the steel traditionally used to forge Japanese swords, prior to the importation of steel from overseas, beginning with products from the Andrews Steel mill in England. Indeed, at one time this product was used for all steel production in Japan.
Before Admiral Perry’s black ships re-opened the many kingdoms and fiefdoms scattered across the islands that now comprise modern Japan, the only significant local source for iron was a material called Satetsu, a loose surface iron written 砂鉄 in Chinese characters, meaning ”sand iron,” and pronounced sah/teh/tsu. Satetsu looks exactly like black sand. It is quite common throughout the world, as you may discover if you drag a magnet through a dark sandy river or over a black beach.
Typically found in rivers and estuaries, for many centuries the area around Yasugi City in Shimane Prefecture was a prime source.
Satetsu was historically harvested in Japan using dredges and sluices creating horrendous environmental damage. Fortunately, the days of wholesale estuary destruction are in Japan’s past.
Although Aluminum is the most abundant metal found on the third rock from the sun, iron is said to make up 34% of the earth’s mass. Japanese satetsu as harvested is a fairly pure form of iron lacking nearly all the problematic impurities typically found in iron ore extracted from mines.
Historically, satetsu was refined in rather crude furnaces called ” tatara” yielding clumps of brittle, excessively-high carbon steel. This “bloomery” technique is not unique to Japan, although many Japanese mistakenly believe it is.
Steel produced this way in the West is called “bloom steel.” Blacksmiths hammer, fold, and re-hammer these crumbly lumps to remove impurities and reduce/distribute desirable carbon forming the more homogeneous Tamahagane steel. This webpage has some interesting photos of tamahagane.
Tatara furnaces are still operated today producing Tamahagane in limited quantities for use by registered sword smiths. Tool blacksmiths use Tamahagane occasionally too out of interest in traditional materials and methods. It is expensive and difficult to work, with lots of waste.
A sawsmith on the island of Shikoku in Japan who was active both before and after the availability of British steel is recorded as saying that imported Western steel increased saw production efficiency in his area tenfold. Clearly, Tamahagane was a very labor intensive material.
Mr. Kosuke Iwasaki, a famous Japanese metallurgist and blacksmith, described forging Tamahagane as being like “hammering butter” because it flattened and spread too quickly and unpredictably, at least compared to modern steels.
Besides its peculiar forging characteristics, compared to modern tool steels Tamahagane is a difficult material infamous for being easily ruined and extremely sensitive to temperature during all phases of forging and heat treatment. These traits have created a traditional sensitivity among Japanese blacksmiths regarding precise temperature control, a beneficial habit when working the tool steels discussed herein.
In use, tools made from Tamahagane behave differently from modern commercial steel, or so I am told. I own and use a straight razor custom forged from Tamahagane for me many years ago by Mr. Iwasaki. I also own antique Scheffield and German razors, but my hand-forged Iwasaki razor puts them all to shame in terms of sharpness, edge retention, and ease of sharpening. I also own a couple of antique Tamahagane saws, but I have not used them much, nor have I used Tamahagane chisels, planes or knives, so my experience is limited to this one wickedly sharp little blade.
Why do I bother Gentle Reader with this story of ancient techniques and obscure products no longer viable? Simply because Tamahagane and the cutting tools and weapons it was once used to produce profoundly influenced both Japan’s history and the Japanese people’s attitude towards weapons and cutting tools, in your humble servant’s opinion.
Although imported Western steel served Japan well during its ramp-up to modernity, the memory of the performance of cutting tools made from Tamahagane remained alive in the national memory. Indeed, I am convinced the Japanese people’s love and fear of sharp things is not only psychological but genetic, although I have not seen any studies on the “sharpness gene.” But that’s a story we should save for the next time we are enjoying a mug of hot coco together around the iori fire on a moonlit Autumn night. May that evening come soon.
Modern Japanese Tool Steels
Enough ancient history. Let’s jump back into the tardis and travel to the late 1950’s to consider a few modern steels. Yes, you can turn your mobile phone back on once inside, but reception may be poor for a few centuries. No you can’t bring back souvenirs. I don’t care what Doctor Whatsit did with his tardis, we are responsible time travelers and will avoid creating causal conundrums. Besides, the import taxes are pure murder. And please, do be careful no little children slip inside with you.
When Japan began to mass-produce commercial steel from imported pig iron using modern techniques, the first standard tool steel produced was identical to Western steels, including the impurities. These are still produced today as the “SK” series of steels as defined by Japan Industrial Standards (JIS).
Eventually, to satisfy the irrepressible sharpness gene of their domestic customers, Japanese blacksmiths and tool manufacturers pressured Japanese steel companies to develop products with fewer impurities and with performance characteristics approaching traditional Tamahagane.
Rising to the challenge, Hitachi Metals endeavored to replicate the performance of Tamagane using modern smelting techniques and imported pig iron and scrap metal instead of expensive and environmentally unsustainable satetsu.
Hitachi purchased and modernized an old steel plant in Yasugi City for this purpose. They formulated the best steel they could make using the best pig iron they could find, mostly from Sweden, an area famous for hundreds of years for producing especially pure iron ore. The results were Shirogami Steel (pronounced she/roh/gah/mee/koh 白紙鋼), Aogami Steel (pronounced aoh/gah/mee/koh 青紙鋼), and Kigami Steel (pronounced kee/gah/me/koh and written黄紙鋼) meaning “Yellow Label Steel.” Later, they developed Aogami Super steel (青紙スパー ) and Silver Label Steel (stainless steel). Each of these products are available in various subgroups, each having a unique chemical formulation.
For a time, Hitachi marketed some of these steels with the “Tamahagane” designation. Problematic, that. Indeed, many saws and knives were stamped “Tamahagane” when these steels were first introduced.
With the explosive popularity of Japanese knives overseas, several Japanese manufacturers have once again adopted the deceptive practice of labeling their products as being made from “Tamahagane” despite being made of common steels and even stainless steels. Because these spurious representations were and continue to be made for the purpose of increasing profits for companies that clearly know better, in your humble servant’s opinion even the stinky label of BS is too good for them.
Caveat emptor, baby.
We tend to think of steel as a hard metallic thing, but lo and behold, ’tis a chemical compound!
Few chemicals humans dabble with are absolutely pure, and while White Label, Blue Label, and Yellow Label steels contain exceptionally low amounts of undesirable contaminants, they do exist. Dealing with the negative impacts of these impurities has been the bane of blacksmiths since Vulcan wore linen nappies.
The most common undesirable impurities found in commercial iron include Phosphorus (reduces ductility, increases brittleness, and messes with heat treating), Silicon (a useful chemical that increases strength, but too much decreases impact resistance), and Sulfur (a demonic chemical that reduces strength, increases brittleness and gleefully promotes warping). Obviously, something must be done about these bad boys.
Some people imagine that, through the Alchemy of Science (a term that’s recently lost nearly all its value nowadays through adulteration and profiteering by dishonest “scientists”), impurities are simply “disappeared” from steel during smelting. While some impurities can be eliminated through heat and chemical reactions, it is not possible to reduce the content of those listed above to insignificant levels through smelting alone.
Undesirable chemicals, including those listed above, can be tolerated in steel to some degree because, like arsenic in drinking water and carbon monoxide in air, below certain levels they cause no significant harm. The best solution we have discovered is to reduce the concentration of impurities to acceptable levels by using ore and scrap material that contains low levels of impurities to begin with, and constantly test, and either reject or dilute the ”pot” as necessary to keep impurities below acceptable levels. This practice is known as “Solution by Dilution.”
White Label steel is plain high-carbon steel without other additives, while Blue Label, Silver Label, and Aogami Super steels have various chemicals added to achieve specific performance criteria. Please see the flowchart below.
Production Flowchart of Yellow Label, White Label, Blue Label, and Super Aogami Steels
Another technique used to mitigate the negative effects of impurities found in iron ore is to add chemicals such as chrome, molybdenum, vanadium, tungsten, etc. to the pot producing so-called “high-alloy” steels that can be more predictably forged and heat-treated, are less likely to crack and warp, and will reliably develop useful crystalline structures despite detrimental impurities. Such high-alloy steels can reliably produce useful tools in mass-production situations by unskilled labor and with minimal manpower spent on quality control. But regardless of the hype, such chemicals do not improve sharpness or make sharpening easier, important considerations in the case of woodworking tools. Indeed, the exact opposite is true.
The table below is a summary of a few tool steels in Hitachi Metal’s Japanese-language catalogue. A PDF can be found at this LINK.
Gentle Reader will notice that White Label and Blue Label steels both have the same minute allowable amounts of impurities such as Silicon, Phosphorus, and Sulfur.
Chemical Table of White Label, Blue Label and Aogami Super Steels
Chemical Table of White Label and Blue Label steels as well as Aogami Super (this table can be scrolled left~right)
Carbon of course is the element that changes soft iron into hardenable steel, so all five steels listed in the table above contain carbon, but you will notice that White Label No.1 has more carbon than White Label No.2. Likewise, Blue Label No.1 has more carbon than Blue Label No.2.
The greater the carbon content, the harder the steel can be made, but with increased hardness comes increased brittleness, so White Label No.1 is likely to produce a chisel with a harder, more brittle blade than one made of White Label No.2.
With impurities and carbon content the same, the chemical difference between White Label No.1 and Blue Label No. 1 then is the addition of chrome and tungsten, elements which make the steel much easier to heat treat, and reduce warping and cracking, thereby yielding fewer defects with less work. Chrome, and especially tungsten, are expensive chemicals that make Blue Label steel costlier than White Label steel, but with easier quality control and fewer rejects, overall production costs are reduced.
White Label No.2 steel makes a wonderful saw, but the plates and teeth of saws forged from White Label No.1 tend to be fragile unless the blacksmith removes excess carbon during forging to improve toughness. This is entirely within the skillset of an experienced blacksmith, and can even occur by accident.
In the case of chisels, plane blades, and kitchen knives intended for professional use, White Label No.1 is the first choice of Japanese professionals followed by Blue Label No.1 steel.
Where high performance at less cost is required, Blue Label No.1 is often preferred.
All things considered, and this is a critical point to understand, compared to White Label steel, Blue Label steel is easier to forge and heat-treat, with fewer rejects, making it a more productive material despite being a more expensive. Indeed, many blacksmiths and all mass-producers prefer Blue Label steel over White Label steel, when given a choice, because it is easier to use and more profitable, not because it makes a superior blade.
Many wholesalers and retailers insist that Blue Label steel is superior to White Label steel because, as a material, it is costlier and contains elements that make it more resistant to wear and “abrasion,” intimating that it will stay sharper longer. Those poor derelict souls who are easily deceived, have less than professional sharpening skills, or do not follow this blog may accept this convenient marketing ploy. But when wise Gentle Readers hear this sort of nonsense they will know to quickly put on their flippers and floaties in time to keep their heads above the stinky, brown flood of BS about to engulf them.
Wise Beloved Customers who choose blades forged from Blue Label steel will do so because they know that Blue Label steel makes a fine blade at less cost than White Label steel, not because Blue Label steel blades are superior in performance. Moreover, regardless of the steel used, they will always purchase blades forged by blacksmiths that possess the requisite dedication and have mastered the skills and QC procedures necessary to routinely produce high-quality blades from the more temperamental White Label steel. The reasons are made clear in the Technical Example below.
Quenching & Tempering
The process of hardening steel, called “heat treatment,” (in Japanese “netsu shori” 熱処理）is key to making useful tools.
High-alloy steels vary in this regard, but in the case of plain high-carbon steels, the two primary stages (with various intermediate steps we won’t touch on) of heat treatment are called “quenching” and “tempering.”
In the case of quenching, the steel blade is heated to a specific temperature, maintained at that temperature for a set amount of time, and then plunged into either water or oil, locking the dissolved carbon in the steel forming a rigid crystalline structure containing hard carbide particles.
After this process the steel is brittle enough to shatter if dropped onto a concrete floor, for instance, and not suitable for tools, so further measures are necessary.
The next step in the heat-treatment process is called “tempering,” a process that adjusts the rigid crystalline structures created during the quench, losing some carbides, but making the steel less brittle and much tougher.
This is achieved by reheating the steel to a set temperature for a set period of time and then cooling it in a specific way. This heating and cooling process can happen in air (e.g. oven), oil, or even lead. All that really matters is the temperature curve applied. Every blacksmith has their own preferences and procedures.
With that ridiculously overly-simplified explanation out of the way, let’s next take a gander at the “Quench Temp” row in the table above which indicates the acceptable range of temperatures within which each steel can be quenched to successfully achieve proper hardness. These ranges are important because if quenching is attempted outside these ranges, hardening will fail and the blade may be ruined.
In the case of White Label steel, Gentle Reader will observe that the quenching temperature range is listed as 760～800°C, or 40°C. Please note that this is a very narrow range to both judge and maintain in the case of yellow-hot steel, demanding a sharp, well-trained eye, a good thermometer, proper preparation, and speedy, decisive action, not to mention a thorough purging of iron pixies and malevolent spirits from the workplace.
Just to make things worse, even within this allowable range, a shift of temperature too far one way or the other will significantly impact the quality of the resulting crystalline structure, so the actual temperature variation within the recommended quench temp range an excellent blacksmith will aim for is more like ± 10˚C.
In the modern world with easily-controlled gas fires, consistent electric blowers, and reliable infrared thermometers, this target can be hit through training and diligent attention, but not that long ago it was seen as a supernatural achievement performed in the dark of night by wizards. I kid thee not.
Compare this range of quenching temps to those for Blue Label steel with an acceptable quenching temperature range of 760～830°C, or 70°C of range, a 75% increase over White Label steel. That’s huge.
Let’s next consider the recommended tempering temperatures.
For White Label steel, Hitachi’s recommended tempering temperatures are 180～220°C, or 40°C of range. Blue Label steel’s temperatures are 160～230°C, or 70°C of range, once again, a 75% greater safety margin.
The practical temperature range for quenching and tempering Blue Label steel is still quite narrow, but this increase in the allowable margin of error makes the job a lot easier, such that Blue Label Steel is much less risky to heat-treat successfully than White Label steel.
Judging and maintaining proper temperatures during forging, quenching and tempering operations is where all blacksmiths, without exception, fail when they first begin working plain high-carbon steel. The guidance of a patient master, time and perseverance are necessary to develop the knack. Experience matters.
I hope the discussion this far at least partially brings into focus the challenges these two steels present to the blacksmith.
If you seek greater light and knowledge, please look online to find similar data for many of the popular high-alloy tool steels. Comparing those numbers to White Label steel and Blue Label steel will help you understand why mass-producers of tools, with their lowest-possible-cost mindset, minimal quality control efforts, and virtually untrained workforce of peasant farmers, lawn-care professionals and fast-food restaurant workers prefer them for making the sharpened screwdrivers represented as chisels nowadays.
Warping & Cracking
A huge advantage of chrome and tungsten additives is that they reduce warping and cracking significantly. This matters because a blacksmith using a plain high-carbon steel like White Label steel must anticipate the amount of warpage that will occur during quenching, and then shape the chisel, knife, or plane blade in the opposite direction so that the blade straightens out when quenched. This exercise requires a lot of experience to get right consistently, making White Label steel totally unsuitable for mass-production.
Steel is a magical material. When yellow hot, the carbon dissolves and disperses relatively freely within the iron matrix. Anneal the steel by heating it and then slowly cooling it and the carbon molecules will migrate and gather into relatively isolated clumps with little crystalline structure leaving the steel soft.
But if the steel is heated to the right temperature and suddenly cooled by quenching, the carbon is denied the time and freedom available it during the slower annealing process, instead becoming locked into the iron matrix forming a hard, rigid crystalline structure. This rigid iron/carbon crystalline structure has a significantly greater volume than pure iron, which is why the blade wants to warp when quenched.
Adding chrome and tungsten and other chemicals reduces this tendency to warp.
Sword blades are an interesting example. A Japanese sword blade is typically shaped either straight or curved towards the cutting edge before quenching, but during quenching the blade warps and curves without encouragement from, and despite the efforts of, the blacksmith. The skill and experience required to accurately anticipate the degree of warpage generated and the resulting curvature of the blade, and then compensate while shaping the blade before quenching to achieve the desired curvature post-quench is not something one learns in just a few months or even years.
Unlike Tamahagane, however, modern high-alloy commercial steels contain large amounts of chemicals such as chrome, tungsten, molybdenum, vanadium, etc., with the result that tools made from these steels warp less, and exhibit far fewer shrinkage cracks.
Aogami Super is another HML product listed in the table and flowchart above. It’s an interesting steel, containing more carbon than both White Label steel and Blue Label steel and a lot more tungsten than regular Blue Label steel. Consequently, it is even more expensive. Aogami Super was originally developed as a high-speed tool steel especially resistant to wear. There are much better steels available for this role now, but Aogami Super is still hanging in there.
But all is not blue bunnies and fairy farts because high-alloy steels have some disadvantages too.
Those who hype high-alloy steels always praise to the heavens the “wear-resistant” properties Chrome and Tungsten additives afford. When the subject is woodworking handtool blades, however, please understand the meaning of “wear resistant” includes “not very sharp,” and “a bitch to sharpen by hand.”
Tungsten makes the steel warp less and expands the heat-treat and tempering temperature ranges significantly leading to fewer defects during production. But the addition of tungsten also produces larger, tougher crystals that simply can’t be made as sharp as White Label No.1, and that makes the blade much more difficult, unpleasant, and time consuming to sharpen, all while wasting more sharpening stone material in the process.
White Label steel has no additives other than carbon. It does not need additives to compensate for or to dilute impurities because its production begins with exceptionally pure pig iron, and carefully tested and sorted scrap metal. Both White Label and Blue Label steels, if properly hand-forged and heat treated by an experienced blacksmith with high quality standards, will have many more and much smaller carbide clumps distributed more evenly throughout the iron crystalline matrix producing a ” fine-grained” steel of the sort coveted since ancient times.
On the subject of scrap metal, this is not necessarily a negative thing. In fact, nearly all tool steels available nowadays contain high percentages of scrap metal content because it is simply too cost-effective to ignore. Careful sourcing and testing are the keys to using scrap metal advantageously.
I hope Gentle Reader found our little excursion back in time in the tardis, and the chemical information presented above, interesting, but it may not have clearly answered your questions about the performance differences between these steels, and when presented a choice, which one you should purchase. Your humble and obedient servant has been asked and answered these questions hundreds of times, and while only you can decide which steel is best for you, I will be so bold as to share with you the viewpoint of the Japanese blacksmith and woodworking professional.
Long story short, in the case of planes and chisels, the typical choices of steel are still White Label No.1, White Label No.2 or Blue Label No.1. These steels will not be available much longer.
If you are dealing with honest blacksmiths and honest/knowledgeable retailers with experience actually using, not just talking about and selling, tools, you will have observed that a specific plane blade, for instance one made from Blue Label steel, will cost less than the same blade made from White Label steel, despite Blue Label steel being a more costly material.
At C&S Tools a 70mm White Label No.1 steel plane blade cost 77% more than one made from Blue Label No.1. This means that the blacksmith’s average cost in terms of his labor (overhead, forging and shaping costs being equal) is also around 77% greater than Blue Label steel, a direct reflection of his potential additional time expenditure and material wastage due defects such as cracking or excessive warping. This a constant risk for the blacksmith making professional-grade blades, the mitigation of which he must include in his production costs if he is to continue to keep a roof over his family’s heads.
So the dishonesty of charging more for products forged from Blue Label or Aogami Super steel is repugnant to your humble servant and should be to Beloved Customers too. But I digress.
White Label steel simply warps and cracks more, but when failure occurs it only becomes apparent after all the work of laminating, forging, shaping and quenching are complete. Ruined steel cannot be reliably re-forged or re-used, so all the material and labor costs up to the point of failure are simply wasted like an expectation of honest news from CNN. It is not a material for careless people or newbies.
So if White Label steel blades are riskier to make, with more wastage, and therefore more expensive, what are the performance characteristics that make White Label steel blades a favorite with professional Japanese craftsmen?
First, properly made White Label steel blades can be made sharper. This makes the craftsman’s work go quicker and more precisely. But don’t forget that this additional sharpness is entirely dependent on the user’s sharpening skills and his willingness to maintain his blades at that higher level.
Second, properly made White Label steel blades are quicker and more pleasant to sharpen, making it easier to routinely obtain the extra sharpness mentioned in the previous paragraph. That sums it up.
To some people, especially those that use edged tools professionally all day long, these differences matter a great deal; To others, not so much.
Is White Label steel worth the extra cost? I think so, but the performance differential is not huge, and only someone with advanced sharpening skills will be able to take full advantage of the difference. For most people on a tight budget, or in the case of woodworking situations where sharpness is not critical, and sharpening speed and pleasure are not driving factors, then a less-expensive Blue Label steel blade is perhaps a better choice. It absolutely makes a fine tool that does a great job of cutting wood.
The Wise Man’s Q&A
Let’s shovel some more BS out of the way by performing the mandatory experiment of taking a hypothetical high-quality White Label steel blade and a hypothetical high-quality Blue Label steel blade, sharpening them identically using the best stones and advanced technique, test them to cut some wood, and then consider the answers to the following two important questions:
Question 1: Will the additional sharpness obtainable from a White Label steel plane blade create a smoother, shinier finish surface on wood than a Blue Label steel blade?
Answer 1: Definitely no; But since the blade started out a little sharper, it will cut wood a little better, a little longer. These results will depend on the skills of the user, of course.
Question 2: In the case where edge-retention, cutting speed, and cutting precision are more important than a shiny finish, which absolutely applies to chisels and knives, will the additional sharpness of a properly made and proficiently sharpened White Label steel blade improve a woodworking tool’s cutting speed, edge-retention, precision and control?
Answer 2: Absolutely yes; On condition that the user possesses and exercises the skills to achieve and maintain that extra degree of sharpness. There is a reason sharpening has always been the first essential skill in woodworking.
These are the reasons why we don’t even offer chisels made from Blue Label steel, or even White Label No.2 with its lower-carbon content, and resulting reduced hardness.
But whether plane blade, chisel or knife, a properly forged and heat-treated blade made by an experienced professional blacksmith from simple White Label steel will always be quicker and more pleasant to sharpen than one made of Blue Label steel with its added sticky chrome and hard tungsten. To the professional that has the need for the additional sharpness, and also possesses the skills necessary to produce and maintain it, that’s a difference many find worth the extra cost.
I daresay many of our Beloved Customers agree.
A Technical Example
You may find the metallurgical technical terms below difficult to follow, but perhaps an example with pretty pictures will help bring things into focus. Please see this informative article by Niigata Prefecture’s Prefectural Central Technical Support Center. If you input the URL into Google and use the translate feature a decent English-language version may magically appear. Or not. Some of the key results are copied below.
The steel being tested in the study outlined below is White Label No.2 steel (row 2 on page 4 of the Hitachi catalogue pdf). They heat-treated seven samples, tested their hardness, and listed the results. In each case, the quench temp varied from 750˚~900˚C (1382˚~1652˚F) in water, but the tempering temp was kept constant at 180˚C (356˚F).
The best results can be seen in Figure 4 below at a tempering temperature of 775˚C (1427˚F) producing the finest, most uniform crystalline (Austentite) structure. Lower temps are not as good. Higher temps are worse. A 25˚ variation one way or the other made a big difference.
So let’s examine how the crystalline structure changes with different temperatures as seen in the photos below.
The white stuff visible in the photographs is Ferrite (iron), while the black stuff is spherical carbide (Cementite). When Ferrite and Cementite meld, a desirable hard crystalline structure called Martensite is formed, although there are several steps in between we will not touch on. This subtle molecular change is the essence of the ancient Mystery of Steel, and the keystone to modern civilization.
Fig.1 shows the steel before heat treatment begins. Notice how the soft iron Ferrite and spherical carbon Cementite are isolated from each other indicative of little crystalline structure and a soft metal. No significant Martensite is visible.
The graph in Fig.2 below shows Vickers Hardness on the vertical axis and quench temperature (with a 20 minute soak) on the horizontal axis. Notice how hardness makes a big jump between 750˚C and 775˚C. This 25˚ range is the sweet spot.
Fig. 3 below shows the crystalline structure at a quench temp in water of 750˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. This is 10˚C below the manufacturer’s recommended quench temp. Notice how the iron Ferrite and spherical carbon Cementite are mixing, forming some gray-colored Martensite, but there are still big lakes of Ferrite visible. Better, but not yet good.
Fig. 4 below shows the crystalline structure at a quench temp in water of 775˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. Notice how the iron Ferrite and spherical carbon Cementite are well-mixed forming pretty grey Martensite, indicating that this is close to the ideal quench and tempering protocol; The sweet spot. The crystalline structure shows few lakes of iron Ferrite or islands of spherical carbon. This organization is typical of durable, hard, fine-grained steel. A mere 25˚C increase in quench temp has yielded a large improvement.
Fig. 5 below shows the crystalline structure at a quench temp in water of 800˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. This is still within the quench temp range recommended by Hitachi. Notice how the Ferrite and spherical carbon Cementite are still fairly well-mixed, but the dark spherical carbon is becoming a bit more isolated from the Ferrite forming more, darker groupings. While the Martensite formed is still quite adequate, the performance of this steel may not be as ideal as that in Fig. 4. Notice also that the hardness of the steel has dropped slightly.
Fig. 6 below shows the crystalline structure at a quench temp in water of 825˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. Notice how the crystalline structure has become less uniform than in Fig 5 after only a 25˚ increase in quenching temp.
Fig. 7 below shows the crystalline structure at a quench temp in water of 850˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. This time, a mere 25˚ increase in quenching temp has resulted in significant degradation in the uniformity of the crystalline structure as well as reduced hardness.
Fig. 8 below shows the crystalline structure at a quench temp in water of 875˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. Once again, significant degradation in the uniformity of the crystalline structure and loss of Martensite is apparent.
Fig. 9 below shows the crystalline structure at a quench temp in water of 900˚C, after a 20 min. soak, followed by tempering at 180˚C for one hour, followed by air cooling. Gentle Reader will notice the many white “tissues” that have developed in addition to tempered martensite. The fibrous-appearing white stuff is considered retained Austenite, a formation that can later be converted into hard Martensite with some effort. Once again, just a 25˚ increase in quenching temp has resulted in significant degradation in the uniformity of the crystalline structure as well as reduced hardness.
Clearly, Shirogami No.2 steel is a very good tool steel, but it’s sensitivity to heat-treatment technique, and the necessity for knowledge, experience and care in working it are also clear.
What should Gentle Reader take away from this technical presentation?
The first thing to understand is that plain, high-purity, high-carbon steel that has been skillfully forged, quenched and tempered will exhibit the finest, most evenly-distributed hard carbides in a uniform crystalline steel structure mankind can economically produce. Such steel will become sharper than any other metal from which a practical chisel or plane blade can be forged.
This fact has not changed since ancient times, regardless of the hype and marketing of the mass-producers who can at best achieve comparatively mediocre results using modern high-alloy steels.
The second thing to understand is that, while it is not difficult to make high-carbon steel hard, nor to temper it to make a durable product, producing a uniform, durable crystalline structure that will become very sharp, will be especially resistant to dulling, and can be sharpened quickly requires serious skills of the sort that only result from many years of study under a master, and dogged commitment to quality control, especially temperature control and timing. In your humble servant’s opinion this makes chisels, plane blades and handsaws hand-forged from the high-quality high-carbon steels discussed in this article worthy of consideration by professional woodworkers who need sharp blades and have the skills necessary to maintain them properly.
If steel is the lock, then the crystalline structure the blacksmith creates in high-carbon steel through his skill, diligence and dedication is the key to the Mystery of Steel. It’s a lock and key mankind has been using since ancient times, a combination that is the foundation of our modern, extremely wealthy civilization. But it’s only been a handful of decades since we developed the technology that made it possible to really understand why the key opens the lock. Rejoice, Gentle Reader, for you live in technologically enlightened times!
I hope this discussion has been more helpful than confusing.
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