The Mystery of the Brittle Blade

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 seek to unravel for Gentle Reader another aspect of 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 he imagines. 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 need to solve the mystery of 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 the battlefield; “I have been betrayed!” he screams 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 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.

The Questions

A Japanese blacksmith fluxing and placing a piece of high-carbon steel onto a hot piece of jigane in preparation for forge-welding the lamination of a blade.

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.

  1. 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;
  2. 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;
  3. 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;
  4. 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;
  5. How did the edge fail? Did it crumble? Chip? Roll? A combo failure (with cheese)? This will tell us a lot about the tool.
  6. 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 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;
  7. 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 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 or a can opener, 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 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, mediocre tools are simply more profitable. 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 deluded, wandering souls who judge performance based solely on lowest cost buy them by the ton. More now than ever, sustainability is given pious-sounding 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 kakuuchi oiirenomi chisel by Hidari no Ichihiro
An Atsunomi chisel by Hidari no Ichihiro

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 the Mystery of the Brittle Blade, but I can 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?”

A shinogi oiirenomi chisel blade by Hidari no Ichihiro

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 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 elasticly deform without fracturing. To “elasticly deform” means an object changes shape or deforms when pressure is applied, but returns to its original shape when the pressure is removed. For instance, 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 may exhibit 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 plasticly, 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.

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?

Solution 3

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.

Solution 4

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!

Rejoice Greatly!

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 from Woody’s cooler over there to wet my whistle. 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 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.

YMHOS

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.

A kakuuchi oiirenomi chisel by Hidari no Ichihiro

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.

Relevant Posts:

The Story of a Few Steels

Professional-grade Tools

The Care and Feeding of the Wild Mortise Chisel – Part 1

Sukezane brand 9mm mortise chisel (mukomachinomi) side view

It is well with me only when I have a chisel in my hand

Michelangelo 1475-1564

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 even seen one.

In this post we will briefly examine 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 Japanese Mortise Chisel. 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 “Splish 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 it is fixed (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 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.

Some Background

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 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. Perhaps it will be canonized some day (ツ)

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 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 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, oiirenomi or atsunomi are more efficient.

Japanese Mortise Chisels

12mm mortise chisel (mukomachinomi) Face View
12mm mortise chisel (mukomachinomi) Side View
12mm mortise chisel (mukomachinomi). Please notice the rectangular cross-section precise right angles, and straight, clean sides. This is the most precise of the Japanese 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.

Nora Brand 6mm Mortise Chisel (Mukomachinomi) Side View
Nora Brand 6mm Mortise Chisel (Mukomachinomi) Ura View
Nora Brand 6mm Mortise Chisel (Mukomachinomi) Shoulder View. Exceptional shaping and filework .

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 aluminum beer cans attract out-of-work divorce lawyers and other such desperate vermin.

See you next time.

YMHOS

Your most humble and obedient servant’s set of well-used mortise chisels. The 8 pieces on the right are by Kiyotada (1.5mm~15mm). The two 2 newer chisels on the far left are by Nora. Over the years I have used these tools both professionally and as a hobbyist more than any other of my chisels, as you can perhaps tell from the differing blade and handle lengths which have become shorter with use. A stoic tool, they gossip among themselves less than most other chisels. Good friends and reliable workmates that helped pay the rent and feed the wife and babies for many years.

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 Mama Shishi bite my head off.

YMHOS

Clean Wood

Redwoods

Infringe upon the rights of no one. Borrow no tool but what you will return according to promise. Take no wood, nor anything else but what belongs to you – and if you find anything that is not your own, do not hide it away, but report it, that the owner may be found.

Brigham Young

In this post your humble servant will offer some advice that, if followed, will save Gentle Readers time, money, and wear and tear on their valuable woodworking tools. These are not original techniques; I stole them long ago from professional woodworkers in Japan. Wise Gentle Readers will be as bold.

Inspection & Questions

Before we go any further, Gentle Reader, do me a favor. Check the soles of your steel planes. Unless they haven’t been used much, you will probably discover scratches, some of them may even be quite deep. Do you think whatever made these scratches might also have dulled the cutting edges of your planes at the same time?

What could have possibly created these scratches? Have iron pixies been using your planes to shave bricks?

Unless you have a serious pixie infestation, it probably wasn’t anything as large as a brick, but rather tiny particles in or on the wood you have been cutting. Could these vicious, hard particles have grown naturally inside the tree the wood you are using came from? Is there anything that grows naturally inside a tree that is harder than a plane blade’s cutting edge and big enough to cause such deep scratches? Perhaps these abrasive particles were maliciously concealed inside the growing tree by compadres of the shambling horde of 6-armed, green-skinned, Fanta-guzzling aliens that follow me everywhere?

Or could the damage have been caused by nails, screws or staples left in the wood? Perhaps. Pixie toenail clippings? Happens more often than we realize. Tiny fragments of a divorce lawyer’s heart? Maybe, but they are rare and tougher than stellite. No, it’s more likely the culprit is something harder and more insidious than even Murphy’s pointy purple pecker, a substance all around us, one we often ignore.

Nitty Gritty

Logging Redwoods in Humbolt County California, 1905

Politics and journalism aside, we live in a dusty, dirty world, and although the steel in your tool blades is very hard, ordinary dust and dirt contain plenty of particles much harder. I guaran-frikin-tee you that collision with even a small particle of mineral grit embedded in the surface of a piece of wood can and will damage a blade’s cutting edge.

You may believe the damage is minimal and of little concern, but every time your blade becomes dull, you must resharpen it. Every sharpening session costs you time pushing the blade around on stones, time not spent cutting wood. And sharpening turns expensive blades and stones into mud. This is time and money wasted, lost forever.

And the abrasive action of dirt and grit embedded in wood is not hard on just chisel blades, plane blades and the soles of steel planes, but is even harder on sawteeth and wooden planes.

The damage is not limited to just your handtools either. Take a closer look at the steel tables of your stationary equipment such as your jointer or tablesaw. Unless they are new, you will find scratches. Has that pervert Murphy been smokin dope and humpin sumpin on your jointer’s bed when you weren’t looking?

Nay, Gentle Reader, supernatural causes aside, and unless you have been grinding legal beagle body parts in your workshop, these scratches are clear evidence that the wood you’ve been working is neither as clean as it looks, nor as clean as it should be. You’ve gotta do something about that.

Ruba Dub Dub

So what can you do? Strange as it may seem, the simplest and surest way to get rid of dirt and grit is to follow your mother’s instructions about the cleaning the bathtub: Simply wash it with soap, water and a scrub brush, followed by a rinse.

Bet you never thought of washing wood before have you?

The idea is to wet, scrub and quickly rinse the dirt and grit off the wood, not to make the wood soaking wet, so none of that “rinse and repeat” nonsense, and don’t get carried away with the hose. A bit of dishwashing soap or borax mixed in the water bucket will help lift out dirt and grit.

Don’t forget to pat each board down immediately afterwards with clean rags to remove surface water. Then separate each board, stand it on stickers on-end, or rest it on-edge, and allow time and circulating air to dry it out of the sun.

Remember to wet both sides of each board to minimize warping. And don’t soak a lot of water into the ends.

Disclaimer: It is not well suited for thin material or laminated wood products that might easily warp, or if you are in a hurry, or if you lack adequate space to properly air-dry the wood. 

Whether you wash the wood with water or not, be sure to do at least the following two steps on every board before you process it with your valuable tools.

Scrub Scrub Scrub

First, use a steel wire brush to dry-scrub all the board’s faces both with and across the grain. Yes, I know it makes the surface rougher. Tough pixie toenails. Scrubbing with a stiff steel brush is extremely effective at removing dust, dirt, embedded particles of grit, and even small stones from long grain. Give it a try and you will both see and smell the dirt and particles expelled. Pretty nasty stuff sometimes.

Saw Saw Saw

Second, and this is supremely important, before planing a board either by hand or using powertools, saw 2~3mm off both ends. This is why you have that circular saw with the carbide-tipped blade. If you can’t do that, at least use a steel block plane, drawknife, or other tool to chamfer all eight corners of the board’s ends to remove both surface dirt and embedded grit.

This step is critical because grit and even small stones frequently become so deeply embedded in endgrain that even a steel brush can’t dig them out. But sure as God made little green apples, Murphy will place them directly in the path of your plane blade.

If you do these things, your tools will thank you over many years with abundant chips, shiny shavings and cheerful little songs. Promise.

Yosemite Valley California, 1865

YMHOS

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