Sharpening Part 11 – Supernatural Bevel Angles

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Pixie, kobold, elf, and sprite, All are on their rounds tonight; In the wan moon’s silver ray, Thrives their helter-skelter play.

Joel Benton

Iron Pixies

Gentle Reader, have you ever placed a tool down, only to later discover it has vanished into thin air? Do your tools ever become unexplainably dull or corroded within what seems like just a few days after cleaning and sharpening them? If so, you may have an Iron Pixie infestation without realizing it. 

Respected fairyologists theorize that, unlike their timid brethren frolicking in forests, or their blingy cousins in Hollywood, New York, and Washington DC who delight in tricking the mass media, film industry and corrupt politicians into constantly making greedy, immoral, hypocritical fools of themselves, Iron Pixies (genus Fatum Ferrum), do not fear iron or iron alloys. Indeed, besides pilfering and concealing tools that contain iron, they love nothing more than to use their corrosive powers to return this metal to its natural state through the thermodynamic chemical process known as “rubeum, et conversus abibo” (turn red and go away).

These piratical pixies become especially joyful if the owner of the snatched tool is unable to find it after much frantic searching, and is eventually forced to buy a replacement. Only when they see the replacement tool will the pernicious pixies permit the owner to locate the pilfered tool, usually rusty and chipped.

We’ll come back to the supernatural aspects of woodworking tools, but first let’s examine some more mundane details about sharpening blades, and a few things that typically go wrong with them.

The Ideal Bevel Angle

There is such a thing as an “ideal bevel angle” for each blade in each cutting situation, one that cuts the wood quickly, cleanly, with minimum force expenditure and that keeps the blade effectively sharp for the maximum amount of cutting possible, but determining this angle is not an easy calculation since it is difficult and expensive to actually observe what is happening at the cutting edge from a shaving’s-eye-view.

For example, a steep  60° bevel angle on a chisel will support the cutting edge thoroughly and will be durable, but it will pound the wood more than cut it wasting time and energy and damaging the wood unnecessarily. On the other hand, a 15° angle will cut well, but is likely to chip and dull quickly. A balance is necessary.

This balance will depend on many factors including hardness and abrasiveness of the wood you are cutting at any time (e.g. Sugar Pine versus Ipe), the quality and nature of your chisel blade, the type of cut you are making (low-pressure surface paring versus high-pressure deep mortises), and the care you take to protect the cutting edge. Yes, technique matters.

Determining the ideal bevel angle is ultimately a trial and error process the diligent craftsman will unconsciously perform until it is second nature, but the following are some general guidelines to get you started.

Most Japanese woodworking tools, including plane blades and striking chisels (oirenomi, atsunomi, tatakinomi, mukomachinomi) perform well in most construction and furniture woods with the standard 27.5°~30° bevel angle. This is a good compromise, acute enough to cut most wood efficiently without too much friction, while still providing adequate support to the thin cutting edge to avoid chipping. 

But like any rule, there are exceptions. For example, 35° is often a superior bevel angle for chisels when quickly cutting mortises in harder woods or planes shaving tropical hardwoods.

When cutting very soft woods, such as Paulownia, similar to balsa wood, a 22~24° bevel angle may work best. 

Paring chisels (tsukinomi), when used properly, are subject to less violent forces than striking chisels, and can handle a 24° bevel angle. But for most woods, a professional-grade Japanese plane or chisel blade will likely experience chipping if the angle is much less. 

There are many variables and potential solutions one might consider, but as a general rule, I recommend starting your experiment with a 27.5~30° bevel angle for plane and chisel blades. 

If you find that your blade chips or dulls quicker than you think it should, increase the angle gradually until it calms down. This can result in a double-bevel blade, one difficult to sharpen freehand. In this case, I fully support using a honing jig, at least until you achieve a flat bevel wide enough and stable enough to sharpen freehand. But don’t handicap yourself by relying solely on honing jigs because they can become like training wheels on a bicycle: slow and childish.

Mercurial Bevel Migration

There is a strange, almost supernatural phenomenon many woodworkers experience, the first evidence of which is a plane or chisel blade that previously held a sharp edge a long time suddenly and unexplainably beginning to dull or roll or chip sooner than before. Even professionals with many years of experience occasionally see their tools exhibit this nasty behavior. 

Some craftsmen faced with this dilemma begin to question their sanity. They may ask themselves: “Has heaven turned its face against me? How do I rid myself of this curse? Do I need to see a shrink?” Other craftsmen, more aware of the dangers of pernicious pixies, draw strange hex symbols on their walls or inlay brass circles and pentagrams into their floors to exorcise them from their workshop. Indeed, this practice has a long history in Europe and America.

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Unfortunately, more than one blacksmith has been falsely accused of poor workmanship when the fault actually lay with the tool’s owner unwittingly allowing Iron Pixies to run amok. If this happens to your tools, please use the methods described below to purge any pestilent pixies in the area.

You would be wise to consider all possible causes of Mercurial Bevel Migration (MBM), including those unrelated to any infernal fiends that may or may not be skulking in your lumber stacks. 

But if not pesky pixies, what else could cause this maniacal metallurgical malfeasance?  Never fear, Gentle Reader, there is another possible explanation, one that can be resolved without paying for years of expensive psychotherapy and mind-altering drugs, or placing small bowls of blood and milk around your workshop, or enduring the pain of tattoo needles, or paying for stinky ceremonies involving burning sage and spirit drums.

The more likely cause is simply that it’s human nature when sharpening chisels and Japanese blades with their laminated, top-heavy construction to apply more pressure to the bevel’s rearward half (farthest from the cutting edge) abrading the softer jigane body more than the harder hagane cutting layer. Eventually, as the soft jigane wears away, the bevel angle will decrease to the point where the cutting edge will lose support and become fragile.

Once you are aware of this tendency and take preventative measures (and assuming you don’t have an iron pixie infestation), all should be well.

Next let’s examine some measures to get rid of both this bad habit and trixy pixies.

Pixie Predation Prevention & Pacification

If you suspect the presence of iron pixies, you should perform a Pixie Detection test. A reliable method is described in the next section below.

In any case, to avoid pixie infestation, you should create a workshop environment unfriendly to pixies. The following is an partial list of measures I have found to be effective.

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Brass bench dogs are an effective pixie repellent
  1. Cleanliness: Clean bench surfaces and sweep the floors daily. Periodically vacuum and wet-mop workshop floors twice a year during the winter and summer solstices (approximately June 21 and December 21);
  2. Add more lighting: Iron Pixies fear light because it reveals them to their enemies;
  3. Keep a pair of boots near the door into the workshop: Pixies are deathly afraid of boots, especially when they contain the feet of sharp-eyed human children, but just the sight of boots will prevent them from entering a space;
  4. Keep brass benchdogs in your workshop. Expert fairyologists insist, and I agree, that having a brass bench dog (remember, Iron Pixies do not fear iron or steel or the IRS) or two close by will banish Iron Pixies to the workshop’s dark recesses and keep their nasty claws away from tools. The deterrent effect of bench cats is unclear, but if you decide to rely on one, be sure it bothers to stay awake;
  5. Welcome spiders: Although this may seem to contradict No. 1 above, Iron Pixies fear spiders, especially daddy longlegs, who tangle them in their webs.
  6. Make regular offerings to the gods of handsaws. More on this subject in future posts.
Richard Kell bevel gauge
A compact and effective brass bevel angle gauge by Richard Kell

A more mundane but sure way to prevent MBM is to make or buy a bevel angle gauge and regularly use it to check your bevels during sharpening. Aluminum, stainless steel or even plastic gauges will work of course, but brass or bronze are more effectual at purging perfidious predatory pixies because copper is toxic and zinc causes pixies indigestion. Be sure to store it close to your valuable steel tools to help repel the maniacal monsters.

Here’s the important thing: once you have this tool on hand, use it to check each blade before, during and after sharpening to ensure you are maintaining the correct bevel angle instead of allowing it to decrease incrementally over repeated sharpening sessions. Make this a firm habit. More on this important subject in future posts.

Remember to measure the bevel angle at the blade’s far right or left edges because the hollow-ground ura of Japanese blades makes it difficult to correctly measure the angle if you check it elsewhere.

Pixie Detection Methods

A serious pixie infestation in a toolchest located in a clothing-optional workshop. Notice the absence of bench dogs, bevel angle gauges and boots in this image.

Iron Pixies are secretive creatures most people never see, but if you suspect you have an infestation, a detection test is called for.

While there are many proven methods to test for pixie infestation, the least expensive non-toxic iron pixie detection test is to sharpen a plane blade, and while doing so, attempt to “stick it” on the stone as in the photo below. This phenomenon is evidence the stone and the blade are in such perfect contact that the suction between the blade, water and mud on the stone’s surface strong is enough to support the weight of the blade.

No, this is not a trick photo with concealed supports, superglue, or photoshop enhancements. The blade is “stuck” to the wet stone’s surface. This is a rite of passage those who wish to become proficient in sharpening must accomplish, iron pixies or no. Not recommended for potato chip-thin Bailey-style plane blades.

If you are unable to accomplish this marvelous feat even after many attempts, you can be assured of the presence of peevish pixies nearby. In that case, use the preventative measures listed in the section above. You should also flatten your sharpening stones (especially the rough and medium grit stones) and make sure your blade’s bevel is perfectly flat. Bulging bevels are the pernicious pixie’s playground. (Aha! Iambic pentameter!)

Fair warning: If you stubbornly persist in your efforts to stick a plane blade before purging the area of pixies, they may go berserk to prevent this sublime event from occurring. If that happens, Katy bar the door!

Infernal Pixies! You Shall Not Pass!!

In the next stage of our adventure, we will examine some of the health ailments blades commonly suffer.  High cholesterol in chisels? Planes with pneumonia? Or just toolish hypochondria? Stay tuned to find out more.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located directly below.

Sharpening Part 10 – The Ura 浦

If a craftsman wants to do good work, he must first sharpen his tools.

Confucius, The Analects
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Geographic Ura
Chisel Ura

We talked about the Ura previously in post No. 9. It is a defining detail in most Japanese woodworking blades, and one we must understand if we are to efficiently sharpen them. In his post we will look into this important feature in more detail.

What is the Ura?

Japanese plane and chisel blades have a unique and intelligent design feature at what is called the “flat” on Western plane and chisel blades, called the “Ura” (pronounced oo-rah).

Ura translates into the English language as “bay,” as in a protected area where the sea meets the shore. At the center of the ura is a hollow-ground, depressed area in the hard steel hagane layer that serves two purposes. 

One purpose is to make it easier to keep the blade’s “flat” (the shiny areas surrounding the depression) planar (in the same plane).

If you pay attention when sharpening your wide Western chisels and planes you will notice that, after many sharpening sessions, the blade’s flat, which was once planar, becomes convex with a high point at the flat’s center making it difficult to keep the extreme cutting edge, especially the corners of the blade, in close contact with the sharpening stone. Yikes!

This doesn’t occur because you don’t know how to sharpen your blades, but simply because your sharpening stones/platens/paper tend to abrade the blade’s perimeter more aggressively than the center. The resulting curvature makes it more difficult to polish the flat’s extreme cutting edge. Major buzzkill.

Because of the Ura, Japanese woodworking blades are quickly fettled initially and tend to stay planar without a second thought for many years of hard use, an important benefit if you count your time worth anything.

Another purpose of the Ura is to reduce the square inches or square millimeters of hard steel you must polish during each sharpening session. As you can see from the photo above, the shiny perimeter land is all that touches the sharpening stone. Compare this with the black area which doesn’t touch the stone. That’s a lot of hard steel you don’t have to deal with. Besides making the job easier, it also saves a lot of time when sharpening and helps one’s expensive sharpening stones last longer. Time is money and stones ain’t cheap, as my old foreman used to say. Even if you don’t use your tools to make a living, remember that time spent sharpening is time stolen from the pleasure of making wooden objects.

The Downside Of the Ura

The Ura detail is not all meadow flowers and fairy farts, however, because it does have one unavoidable downside: Over many sharpening sessions the Ura unavoidably becomes gradually shallower, and the lands surrounding the Ura on four sides become correspondingly wider. It is not uncommon to see old chisels and plane blades with the depressed area of the Ura almost gone. You can postpone this day by sharpening the Ura wisely. However, in the worst case where the Ura disappears entirely, you will still be left with an entirely usable Western-style flat, so not all is lost.

In the case of plane blades, unless the plane’s ura is subjected to a brutal sharpening regime, the land that forms the cutting edge (called the “Ito ura” meaning “strand” as in a flat area on a riverside, in Japanese) tends to gradually become narrower, and even disappear entirely after numerous sharpenings. Of course, when this happens, the blade loses its cutting edge, and the land must be restored by “tapping out” or bending the cutting edge towards the ura side, and then grinding it flat to form a new ito-ura land. Tapping out a blade requires some caution, but is not difficult. I will not deal with this aspect of blade maintenance in this post.

In the case of chisels, which have smaller and shallower ura compared to wider plane blades, the land at the cutting edge does not typically require tapping out, although it’s certainly possible to tap out wider chisel blades. Narrow chisel blades, on the other hand, are difficult to tap out without damaging them due to the rigidity produced by the hard steel layer (detailed in the previous post in this series) wrapped up the blade’s sides.

Mitsuura Chisels

Ichimatsu Nomi Ura (by Kiyotada)
Spearpoint Mitsuura chisels by Sukemaru using EDM technology. Sadly, Mr. Usui no longer produces them.

Some chisels are made with multiple ura, typically called “mitsuura” meaning “triple ura.” Mitsuura chisels are more difficult to sharpen because the area of hardened steel that must be polished is larger. The Ura of mitsuura chisels also tend to wear-out quicker than single-ura chisels because each individual ura is shallower in depth than standard Ura. I am not a fan of multiple ura except in a few specific applications.

In the next stage of our journey into the mysteries of sharpening, we will wander through the metaphysical realms of the “Fae.” Be sure to have a brass bench dog in your pocket when we leave the well-lighted pathways.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.

Chisel Handles – The Right Wood

Japanese White Oak acorns

The Right Wood for the Right Place 適所適材

Old Japanese Saying

Our customers outside of Japan frequently need some information to help them select the best wood for their chisel handles. In this post I’ll describe the woods available and the advantages and disadvantages of each to help you make an informed decision.

The chisels we sell all have wooden handles in several varieties of wood, the two most common being Japanese White Oak and Japanese Red Oak. We also can provide handles for some chisels in Gumi (Silverberry wood), Ebony, and Rosewood. Let’s look at White Oak first.

Japanese White Oak

巨樹 シラカシ
Japanese White Oak tree

Japanese White Oak (JWO) is very similar to American White Oak in that it is closed grain, dense, and has medullary rays. The color is a little whiter than the American or European varieties, and in fact, it’s a little denser and stronger than either. It holds up well to being struck with steel hammers.

JWO is not a slick wood when dry and does not become slippery when wet, important characteristics in a tool handle where staying attached to the blade and staying secure in a sweaty hand while being pounded on are part of the job.

Like White Oak everywhere, it contains tannic acid. In fact, bark and chips from this wood have been used since before written history to tan leather because this chemical converts animal skins that would otherwise rot into durable leather. Tannin, which is the base word of both tanning and tannic acid, comes from the medieval Latin word tannāre, a derivative of tannum (oak bark), from which the tannic acid compound is derived.

Tannic acid can react with some people’s sweat causing the wood to turn a dirty grey color. This tendency is not strong among the Japanese people, but it is among many caucasians, including me.

This discoloration in no way weakens or harms the wood, it just makes it look dirty.

JWO generally has a bland, indistinct grain with few flecks, not a problem for a tool handle or plane block, but less than ideal for furniture.

Usunomi with Japanese White Oan handle

Japanese Red Oak

赤樫,どんぐり
Japanese Red Oak acorns

Japanese Red Oak (JRO) is as different from American Red Oak as the “the moon and a mud turtle,” as they say over here. It is a much more useful wood.

Similar to JWO, Japanese Red Oak is closed grain and also has medullary rays. It contains much less tannic acid, and ranges in color from a dark red (difficult to obtain nowadays) to a pinkish red.

JRO has been prized in Japan for tool and weapon handles since forever. Indeed, JRO is the preferred wood for the bokken wooden swords used in the martial arts. The better grades are denser than White Oak with a more interesting grain. Unfortunately, this grade of Red Oak has become difficult to obtain.

Japanese Red Oak tree

As with Japanese White Oak, Red Oak is not a slick wood when dry and does not become slippery when wet.

There are unscrupulous people that dye less colorful pieces of Red Oak a dark red color to jack up the price. We don’t deal with such slimy people and our JRO handles are all authentic. Caveat emptor, baby.

JRO has the advantage of discoloring less than JWO over time and tends to look cleaner longer. It makes a more attractive handle.

赤樫 大木
Japanese Red Oak tree

The downside to the JRO generally available nowadays is that it is a little less dense than White Oak. I consider Japanese Red Oak to be the perfect wood for paring chisels, and Japanese White Oak the perfect wood for atsunomi chisels. Either wood works fine for the smaller oiirenomi bench chisels.

Kotenomi paring chisel with Japanese Red Oak handle

Gumi

Gumi (Elaeagnus multiflora or cherry silverberry) is more a hedgewood or bush than tree. It has historically been cultivated primarily for the fruit it bears. It is stronger than Japanese White Oak, but lighter in weight. It has a distinctive yellow color that some people find attractive. I don’t get the attraction, but must admit it has a striking appearance.

Gumi makes a fine, durable handle. It is a more expensive material. My handlemaker has shorter pieces suitable for oiirenomi handles in-stock, but nothing longer.

Hammer handles of Gumi wood

Gumi handles are custom order.

Ebony and Rosewood

Ebony and Rosewood make elegant, durable, well-balanced handles for paring chisels, which are never struck with hammers and therefore unlikely to crack. But material costs are quite high. They are also custom order items that take some time to fabricate.

Oirenomi and atsunomi and other types of tatakinomi with ebony or rosewood handles look great. And in the case of amateurs that buy such chisels (from other sources) just to collect and/or admire, I have nothing to say. But we sell professional-grade tools to be used on real-world jobsites and in workshops by serious craftsmen for serious cutting, not to become safe queens. Using ebony and rosewood handled oirenomi or other varieties of tatakinomi to do real work is like wearing Jimmy Choo stilletto heels to a construction site.

Yes, Jimbo makes elegant shoes. And if your ensemble is well thought-out, a pair of his heels will make your legs look mahvelous dahling, simply mahvelous. Sadly, they will neither last long nor get the job done. Other workers will mock you behind your back. And embarrassing stuff will happen at the worst possible time.

Women. simply do not belong on construction sites... This is a scene from a TV show called Parks and Recreation. This woman is an actor. This woman was paid to fall like that. That woman is not actually that dumb.
Well…. that was embarrassing!

For warranty reasons, we do not sell tatakinomi of any kind with handles of ebony or rosewood. They are too easily and irreparably cracked/damaged if struck with a steel hammer. Professionals will not purchase, and we will not sell, such silly tools.

Customs Duties

While it has not been a problem so far, importation of some exotic hardwoods such as Brazilian rosewood into the United States can be a problem, according to the guitar makers I know and information on the infallible internet (ツ). If you order handles made from these woods, please be aware that you become the responsible importer once such materials cross into the jurisdiction of your local Customs Office. They may confiscate your tools or levy fines. The risk is all yours. That said, it has not been a problem so far.

Not encouraging, I know, but customs services worldwide are in the business of making literally tons of money every hour by taxing the entire world using their absolute authority within their bailiwick, and lots of guns. The most profitable income source for governments, as you know, is not taxes but making and circulating money (literally manufacturing money), followed by customs fees. Such it has always been; such it will always be.

On the other hand, we have experienced difficulties and customs duties in only two countries, namely Spain, which is notorious for once charging confiscatory import duties on gunpowder and cannonballs brought into Spain by Great Britain to free that country from Napolean’s armies during the French occupation.

Australia was brutally difficult on one occasion, but that incident may have been driven more by dazzling government incompetence rather than enforcement of the country’s importation laws.

Conclusion

For standard oirenomi and other tatakinomi intended to be struck with a steel hammer, either White Oak or Red Oak are entirely adequate and cost-effective. White Oak is a little stronger, but its appearance does not improve with use or age. Red Oak is not quite as dense and strong, but it is sufficient for these chisels and looks better over time.

For wider Atsunomi and Mukomachinomi (mortise chisels) which will see heavy use, White Oak is the best choice due to its higher density and superior strength.

If cost and delivery time is not a concern, you like the yellow color and want to be different, then gumi is an excellent choice for oiirenomi. It’s the same as the difference between brown leather work boots and tan-colored Timberland boots.

For usunomi and other paring chisels not intended to be struck with a steel hammer, Red Oak is the best choice, IMO, but White Oak will perform just as well. Gumi is not an option. Ebony and Rosewood look beautiful and feel nice (if you don’t have allergies to Rosewood), but are expensive and require lead time.

I hope this has been helpful.

I remain,

Your Most Humble and Obedient Servant

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

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A piece of hot high-carbon steel, which will become the cutting edge, has been placed on the orange-hot low-carbon steel body of a knife. An acidic flux powder has been placed in-between and on the metals in preparation for forge laminating them together into a single blade.

“It is our choices, Harry, that show what we truly are, far more than our abilities.” 

J.K. Rowling, Harry Potter and the Chamber of Secrets

If you are reading this, it’s safe to assume you are interested in sharpening woodworking blades. You may have little experience with Japanese tools, and even then you may not be aware of some of their important details. In this post we will try to remedy that by examining some simple historical points common to woodworking blades around the world, as well as some details that make Japanese blades unique.

I believe an understanding of these basic facts will you aid your sharpening efforts, or will at least tickle your interest in Japanese blades. Please comment and let me know your thoughts.

Laminated Bi-Metal Construction

As discussed in previous posts in this series, before technological advances in the 1800’s steel was difficult to make and expensive. Consequently, it was standard practice not only in Japan, but everywhere including Europe and the United States, to reduce costs by minimizing the amount of precious steel used to make axe, scythe, plane and chisel etc. blades by laminating smallish pieces of high-carbon steel to softer and much cheaper wrought-iron bodies through a process called “forge welding.”

Most chisel and plane blade blacksmiths in Japan continue to employ this lamination technique even today, not out of some navel-gazing preference for the archaic, but because it has serious advantages.

A 30mm Hidarino Ichihiro Atsunomi, approximately 12″ OAL.

The best Japanese plane and chisel blades are generally comprised of a layer of very hard high-carbon steel called “hagane” (鋼) in Japanese, forge-welded to a softer low-carbon (ideally no-carbon) iron body called “jigane” (地金). We discussed both of these metals in the previous two posts in the series. Here and here.

Why go to so much trouble? One advantage of this construction is that it allows the cutting edge to be made much harder, and therefore cut effectively longer than a blade of uniform hardness. For instance, a blade made entirely of steel hardened to HRC65 might cut very well, but it would break or shatter in use. And even if it did not break, it would be time consuming and irritating to sharpen such a wide expanse of hard steel. Remember, the harder a piece of steel is the more work it takes to abrade it.

A 42mm Hidarino Ichihiro Oiirenomi

By combining a thin layer of this very hard steel with a thicker layer of soft low-carbon steel or wrought iron the blade can be made thick, rigid, resistant to breaking, and will hold a sharp edge relatively longer while still being easy to sharpen. This once-common ancient structure is clearly superior to all other structural systems for planes and chisels at least.

Laminated Blades in the West

If you have examined antique plane blades with wooden bodies you may have noticed many have blades stamped ” Warranted Cast Steel”

Despite being designated “cast steel” in England and America in past centuries, unlike Conan’s Daddy’s sword, or the orc blades made by in Isengard, plane, chisel and saw blades with this mark were not “cast” by pouring molten metal into a mold to form a blade. Rather the process to make the steel involved melting steel in a crucible and pouring it into molds “casting” a piece of high-carbon steel which is then forged to make the blade, hence the name.

This technology was widely used in the United States and Europe through the 1860’s. In fact, one steel mill is said to have been producing crucible steel until the 1960’s. Toolmanblog has an interesting summary on cast steel.

With few exceptions, these plane blades have a thin piece of high-carbon steel forge-welded to a soft wrought iron body, very similar to Japanese plane blades. I have used a couple of these antique blades to make Krenovian planes and testify of their excellent cutting ability.

Chisels were also once made in Europe using this same lamination technique, although fewer examples remain extant.

Axes, hatchets, and many farming implements were also mass-produced up until the 1920’s in the US using a variation of this same technique with a “bit” of steel forming the cutting edge laminated to or sandwiched inside a body of low-carbon steel or wrought iron. Axes are still made this way in Japan. It’s a proven technique with a lot of advantages, but it does require a skilled blacksmith to pull off successfully.

The point I am trying to make is that blades made using forge-welded laminated technology were the very best available in Europe and the United States for many centuries. It is sad that this superior technology has been discarded and forgotten except in Japan, but wars and economics change everything while people remain the same.

Here is a link to a blog post by Paul Sellers where he praises the old chisels and laments the new.

U-Channel Construction

A closeup of the 42mm Hidarino Ichihiro Oiirenomi showing the lamination line between the steel cutting layer and low-carbon steel body of the blade
The same 42mm Hidarino Ichihiro Oiirenomi. Notice the hard-steel lamination wrapped up the blade’s sides to add rigidity.
A 30mm Hidarino Ichihiro Atsunomi, approximately 12″ OAL. Notice the hard steel lamination forming the cutting edge at the bevel. This is a beautiful lamination.
A beautiful hand-filed shoulder detail typical of Yamazaki-san’s work

The shape of the hard steel cutting layer laminated to the softer low-carbon steel (or wrought iron) body was historically a simple flat plate in Western blades. This is also the case for Japanese plane blades, axes, and farming implements. But if you imagine Japanese blacksmiths would be satisfied with such a simple design for all applications, you don’t know the Japanese mind well.

Notice the lighter-colored hard steel lamination wrapped up the chisel’s sides in the four photographs above forming a “U channel” of hardened steel adding necessary rigidity and strength. This is a critical detail for Japanese chisels intended to be struck with a hammer. Interestingly, carving chisels are not typically made this way.

Plane blades are not subjected to the high loads chisels experience and so would not benefit from this structural detail.

The Ura

Japanese chisel and plane blades, among others, typically have a hollow-ground depression called the “Ura” (pronounced “ooh-rah”) which translates to “ocean” or “bay,” located at what is called the “flat” on Western blades. Notice the polished hard steel lamination extending from the cutting edge to several millimeters up the neck. The black area surrounded by the shiny lands is the same hard metal, but has been ground to form a hollow called the “ura.”

This clever and effective design detail is unique to Japanese tools to the best of my knowledge. We will look at this design detail more in the next post in this series.

The Point

What does any of this have to do with sharpening? Glad you asked. This design has some potential disadvantages that have been cleverly turned into distinct advantages you need to understand when sharpening Japanese woodworking blades.

For instance, the layer of high-carbon steel laminated into our chisels and planes is usually 64~65 HRc in hardness. The typical Western blade is made much softer at 50~55 HRc to avoid breakage. This extra hardness makes the blade stay sharper longer, an important benefit if your time is worth anything. This is good.

But if the entire blade were made of a solid piece of this extra-hard steel, it would a royal pain in the tukus to sharpen, I guarantee you. It would also break. That would be bad.

The softer low-carbon/no-carbon steel or iron body, however, is much softer and easily abraded making it possible to keep the hard steel layer thin, and therefore easily abraded, while protecting it from breaking. This is good.

Unlike the blade’s bevel, however, the ura is all one-piece of hard steel. Without the ura depression, you would need to abrade all that hard steel to initially flatten and regularly sharpen the blade, a necessity I guarantee would ruin your mellow mood without massive quantities of controlled substances. But with the addition of the ura detail, we only need to abrade the perimeter planar lands (the shiny areas in the photos above) around the ura. This is exceedingly good.

The ura depression makes it easier and quicker to not only sharpen the blade, but also to to keep the “flat” planar (in a single plane). Without the ura, such a hard blade would be difficult to maintain planar and frustrating to sharpen. With the addition of the ura, the blade is genius.

An important skill to learn when sharpening Japanese blades is how to maintain the lamination and ura effectively. We will discuss this important subject more in future posts.

Conclusion

If you didn’t learn at least three new things from this post then you are either very smart or weren’t paying attention. ¯\_(ツ)_/¯

In the next installment in this bodice-ripping tale of romance and derring-do we will examine the hollow-ground “Ura” in more detail. It’s important enough to deserve a special post.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the question form located immediately below.

Sharpening Part 8 – Soft Iron 地金

If you can’t explain it to a six year old, you don’t understand it yourself.

Albert Einstein

In the previous post on sharpening Japanese woodworking tool blades we looked primarily at the nature of the hard high-carbon steel used in making woodworking blades. In this post I will try to dispel some of the confusion that surrounds the other metal used in making most Japanese knives, axes and woodworking blades, namely the soft low-carbon steel called “Jigane” (地金). I hope this brief explanation will improve your understanding of some Japanese tools and aid your sharpening efforts.

Sources of Jigane

Most Japanese knives and woodworking blades are comprised of a thin piece of hard high-carbon steel, discussed in my previous post, forge-weld laminated to a piece of softer low-carbon steel or wrought iron called “Jigane” (地金) in Japanese, which translates directly to “ground metal.”

I will write more about this bi-metal lamination in the next post in this series, but for now take my word that it is essential to the performance of many types of Japanese cutting tools nowadays, and for many centuries was critical to manufacturing cutting tools in America and Europe as well.

The best jigane material for plane blade bodies is said to be scrap iron from the boilers of old trains, boats, and factories, etc.. Such boiler tanks were subjected to thousands of heating and cooling cycles during their years in service which drove out impurities, including carbon, making the iron very soft to the point of weakness.

The most desirable jigane for plane blades is called “tired” iron, named because it is not only soft, but looks weak and exhibits a visible grain along with cracks and imperfections which those familiar with Japanese plane blades covet.

A pile of jigane, probably old salvaged structural steel. Looks like boards of old wood, but it ain’t.

Wrought Iron Production

Nowadays, this very low-carbon steel, also known as “ wrought iron” is not produced in any volume for several reasons. First, demand is just too low to make it worthwhile to manufacture. Hand-forged ornamental iron is the only commercial usage besides Japanese tools, truly microscopic markets.

The second reason is that steel manufacturing processes have changed drastically in the last 100 years. For instance, it used to be that steel began as iron ore, basically rocks and dirt, which was melted and refined into low-carbon wrought iron, so wrought iron was an intermediate product of steel production. Indeed, this low-carbon product was much less expensive to produce than high-carbon steel and so was used for everything from the boilers, bridges, trains, ships and anchor chains mentioned above to axes, chisels, farming implements, machinery, what’s called “miscellaneous metals” in the construction industry, and of course plane blades. There are still a few surviving structures that were made using this archaic material.

Nowadays, things are very different. Carbon is incorporated into the steel early in the manufacturing process, so low-carbon wrought iron never becomes an intermediate product.

Also, scrap metal has become critical to steel manufacturing processes nowadays. Remember what happened to steel prices worldwide when China was buying up huge volumes of scrap metal worldwide for its Olympic infrastructure building projects?

I think we can agree that this energy-efficient cost-reducing recycling of natural materials, one that was hardly an option 150 years ago, is a very good thing. But it does have a tiny downside, namely that most commercially-available scrap metal available in any useful volume today has been through the modern steel-manufacturing process many times and already contains not only high levels of carbon, relatively speaking, but alloys such as chrome, molybdenum, and nickel from previous melting pots. Indeed, undesirable chemicals such as phosphorus, sulfur and silica tend to be high in general junkyard scrap metal. On the other hand, keeping these unintended alloys and impurities under control is a serious challenge for manufacturers of tool steel.

In summary, wrought iron simply isn’t made anymore, and it is not a sustainable, profitable product.

Japanese blacksmiths making high-quality plane blades nowadays mostly use wrought iron recycled from old anchor chains, old iron bridges, or other recycled iron structural components. If you see a hole in a plane blade, like the extra-wide plane blade pictured at the top, it once housed a rivet. Yes, structural steel was once connected with hot rivets instead of bolts. Hi-tensile modern bolts are better.

Plane Blades

A plane blade by Ogata-san in his “Nami no Hana” series using Swedish Asaab K-120 steel. Notice not only the fissures and defects, but also the striations and grain typical of soft, tired “wrought iron.”

Mr. Takeo Nakano (see his photo below) makes my plane blades. He is a kind, quite man with the outward appearance of a sedentary grandfather, but when using hammer and tongs at his forge within his dark smithy, his posture and visage reminds me of an intense Vulcan reinforcing the gates of Hades.

Like nearly all the plane blacksmiths in Niigata, he uses scrap iron obtained in a single lot many years ago from an iron bridge that was dismantled in Yokohama Japan.

Mr. Nakano at home

I am told that most of the jigane used for plane blades in Hyogo Prefecture is old recycled anchor chains.

The fissured and cracked jigane of a a 70mm plane blade by Usui Kengo, another Niigata blacksmith (RIP). Notice the rod which retains the chipbreaker is non-existent, replaced by two short stubs. An elegant detail in this plane body by Ito-san (Soh 宗).
The back of the same Usui plane blade. Notice the cracks and inclusions in this excellent jigane exposed at the polished bevel. Very wabi-sabi. This jigane was once part of an iron bridge in the city of Yokohama, Japan.

In the case of plane blades, structural strength is not critical, so laminating a thin layer of high-carbon steel to form the cutting edge to a soft iron body is adequate. Indeed, the thicker the hard steel layer, the more time and effort it takes to sharpen the blade, so in a high-quality blade the thicknesses of the high-carbon steel layer and the soft jigane body will be carefully balanced to ensure the blade’s bevel rides the sharpening stones nicely and can be quickly abraded.

Plane blade blacksmiths use the same strip jigane used for chisels for making less-expensive plane blades.

Chisel Blades

In the case of chisels, while ease of sharpening is still important, the body and neck must be harder/stiffer to prevent them from bending, so a different, stiffer variety of jigane with a higher carbon content and fewer defects is used, and the steel layer is typically made thicker.

The jigane used by my chisel blacksmiths is a commercial product not produced anymore (thank goodness they have stockpiles) called “gokunantetsu” 極軟鉄 which translates directly to “extremely soft iron.” With a carbon content of 0.04~0.07%, a better description would be “very low carbon steel.” When heated and quenched, it doesn’t harden much.

The adventure will continue in the next exciting episode where we will bring it all together into a blade. Don’t forget to have popcorn and jujubes ready.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form immediately below.

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

An Alchemist and his assistants working late at night in his workshop.

Behold, I have created the smith that bloweth the coals in the fire, and that bringeth forth an instrument for his work.

Isaiah 54:16 KJV

The blades we are considering in this post are made from iron and steel, so it makes sense to examine these materials from the viewpoints of sharpness and sharpening. In the previous post we looked at some of the supernatural aspects of making and forging steel. In this post we will examine some alchemical aspects.

This post could be very technical, but I have simplified the description of chemical processes to make it easier for the non-technical Gentle Reader to follow. Please bear with me.

The Alchemy of Mutating Iron to Steel

At the heart of steel alchemy is the hardening process. When carbon is combined with iron in the right proportion, steel is formed. This mutation is easily accomplished nowadays, but for most of human history it was a fiendishly difficult, expensive process. No wonder those who could accomplish the deed were attributed with magical powers.

If steel is heated to within a specific range of temperatures (difficult to measure by eye) and then suddenly cooled, crystalline structures containing small, very hard and relatively brittle crystals called carbides form within a softer matrix of iron. These hard carbides are what do the serious job of cutting, not the softer matrix. At the extreme cutting edge, this structure might be compared to a modern circular saw blade comprised of a relatively soft body to which is attached very hard tungsten carbide cutting tips.

A steel blade dulls when these carbide crystals either shatter, or the pressure and friction of cutting wears away or cracks the softer supporting matrix, allowing the carbides to be torn from the matrix leaving behind gaps of soft, blunt metal. The larger the carbide clumps are and the further the distance between them, the more easily they are shattered and torn away, and the duller a blade becomes with each crystal’s failure.

In a low-quality blade, and given the same number of carbide crystals in a fixed volume of steel, the crystals will form into relatively large and isolated clumps separated by wide rivers and lakes of softer metal, as seen from the viewpoint of a carbide. The steel will crack along these weaker pathways when stressed, and when cutting, the softer material in these lakes and rivers will erode first, leaving the carbide clumps unsupported and vulnerable to failure.

In a high-quality steel blade, by comparison, and given the same number of carbide crystals in a fixed volume of steel, the crystalline clumps are comparatively smaller and distributed more evenly throughout the matrix making it more resistant to erosion, and the carbide crystals more resistant to damage. Such steel is called “fine grained,” and has been highly prized since ancient times for its relative toughness and ability to become very sharp and stay sharp for a long time. This is the steel preferred by woodworking professionals in Japan and is the only kind found in our tools. Without exception.

Impurities and Alloys

All iron ores naturally contain harmful impurities such as phosphorus, sulfur, silicon, and manganese to one degree or another. When these impurities exceed acceptable limits, they can weaken the steel, make it brittle, or make heat treatment results inconsistent. They are often expensive to remove.

There are three approaches commonly used to minimize the negative effects of these difficult-to-remove impurities. The first is simple avoidance of the problem by employing iron ore and scrap metal free of excess amounts of these contaminants. Such ore and scrap are available, but they are not found everywhere and are relatively expensive. For centuries, the purest iron ore has been mined in Sweden.

The second approach is to add purer iron or carefully sorted and tested scrap steel to the pot thereby reducing the percentages of the harmful contaminants. This is called “ solution by dilution.”

Nakaya Takijiro’s saw forge, originally made for forging swords

The third and more common fix is to add chemicals such as chrome, molybdenum, nickel, tungsten, vanadium and even lead to the pot forming steel “alloys.” In their simplest formulations, these chemicals help overcome the detrimental effects of natural impurities, specifically those related to brittleness and unpredictable heat treatment results. Some formulations make the steel less likely to warp and crack despite impurities. Others make the steel more resistant to abrasion and corrosion, or even easier to cast, drop-forge, or machine. 

Steel alloys have serious advantages over plain high-carbon steel in mass-production, reducing material costs by improving the performance of cheaper lower-grade iron ore and scrap metal, improving manufacture characteristics, and achieving higher productivity with fewer rejects even when worked by low-skill workers.

But these alloys are not all fuzzy blue bunnies and fairy farts because edged tools made from high-alloy steels typically have some disadvantages too: Due to their crystalline structure, they simply cannot be made as sharp as plain high-carbon steel, and are more difficult and time-consuming to sharpen by hand.

Of course, additives like chrome, nickel, moly and especially tungsten are costly.

Some manufacturers cite the higher costs of high-alloy steels to justify higher prices for their products. However, what they never say out-loud is that labor costs are much much less when using high-alloy steel because skilled workers are not necessary. And because high-alloy steels produce fewer rejects, quality control is easier, overall productivity is higher, warranty problems are fewer, and profitability is increased. Indeed, without high-alloy steels, factories would need to train and hire actual skilled workers and professionals instead of uneducated seasonal workers destroying the world’s current mass-production model. Egads! Walmart’s shelves would be bare!

My blacksmiths make only professional-grade tools for craftsmen that value ease of sharpening and cutting performance above corporate profits. They charge more for plain high-carbon steel blades than for high-alloy steel products because labor and reject costs are higher. So if a manufacturer brags about the excellence of the high-alloy steels they are using rest assured increased profits are their motivation, not improved cutting performance. Caveat emptor baby.

Blacksmith

Japanese Steels

The best plane and chisel blades are made from plain, high-purity, high-carbon steel. In Japan, the very best such steel is made by Hitachi Metals mostly using Swedish pig iron and carefully tested industrial scrap (vs used used rebar and car bumpers), and is designated Shirogami (White-label) No. 1. They also make a steel designated Shirogami No.2 containing less carbon. Another excellent steel for plane and chisel blades is designated Aogami (Blue-label) No.1 and No. 2.

Aogami, like Shirogami, is made from extremely pure iron, but a bit of chrome and molybdenum are added to make Aogami steel easier to heat treat with less warping. Aogami can be made very sharp, but it is not quite as easy or pleasant to sharpen as Shirogami. Some of the plain high-carbon Swedish steels are also excellent.

If worked expertly, either of these steels consistently produce the highest quality “fine-grained” steel blades.

Let’s compare the sharpening characteristics of these two steels. To begin with Shirogami steel is easy, indeed pleasant, to sharpen. It rides stones nicely and abrades quickly in a controlled manner.

Aogami steel, by comparison, is neither difficult nor unpleasant to sharpen, but it is different from Shirogami steel in subtle ways. It takes a few more strokes to sharpen, and feels “stickier” on the stones, but it will still produce fine-grain steel blades and performs perfectly.

Inexperienced people lacking advanced sharpening skills typically can’t tell the difference between blades made from Shirogami, Aogami or Swedish steel and steels of lesser quality. But due to the difficulty of forging and heat treating Shirogami or other plain high-carbon steels, a blacksmith that routinely uses them will simply be more skilled and have better QC procedures than those whose skills limit them to using only less-sensitive high-alloy steels.

Professional Japanese woodworkers insist on chisel blades made from Shirogami steel. Some prefer Aogami for plane blades believing the edge holds up a bit better. My plane blacksmith and carving chisel blacksmith prefer to use Aogami because it is easier to work and more productive (especially in the case of carving chisels), but for a little extra they are happy to forge blades from Shirogami or Swedish Steel.

I own and use Japanese planes made from Shirogami, Aogami, Aogami Super, Swedish steel, and a steel called “Inukubi” meaning “dog neck” which was imported to Japan from England (Andrews Steel) in the late 1800’s. Of these, Shirogami No.1 steel is my favorite. It’s a matter of personal taste.

Beware of a plane blacksmith that refuses to use plain high-carbon steel and tries to charge you more for Aogami or Aogami Super steel.

The Challenges of Working Plain High-Carbon Steel

What makes plain high-carbon steel so difficult to work, you ask? I’ve never even forged a check much less a tool blade, but I will share with you what the blacksmiths I use and swordsmiths I know have told me in response to this question.

First, plain high-carbon steel is much more difficult to successfully heat treat because the range of allowable temperatures for forging and heat-treating is narrow. Heat it too hot and it will “burn” and be ruined. Quench it at too high or too low a temperature and it will not achieve the desired hardness. Miss the appropriate range of temperatures and the blade may even crack, ruining it. Yikes.

Second, even if the temperatures are right, plain high-carbon steel has a nasty habit of warping and cracking during heat treatment resulting in more rejects than steels with additives such as chrome and moly. Strange as it may seem, when the crystalline structures that make steel useful form during quenching, they increase in volume. This change in volume produces differential expansion causing the metal to warp. This warpage can be more or less controlled, or at least compensated for, by a skillful blacksmith, but it takes real skill, extra work, and a bit of luck. Not just any old Barney can do it consistently, so when working plain high-carbon steel, a blacksmith needs to know his stuff and pay close attention.

Other than wastage due to rejects, it doesn’t cost more to forge and heat-treat a blade of plain high-carbon steel. But it takes serious skills and dedication to quality control to make a living working it for 5+ decades.

Let me give you an example of skill and experience as it relates to warpage management of plain high-carbon steel.

The photo below is of a swordsmith the instant before he quenches a yellow-hot sword blade made of tamahagane, a traditional type of plain high-carbon steel made from iron sand, in a water trough. Notice the condition of his smithy: he is working in the middle of the night, the time when the best magicians and alchemists have always done the most difficult jobs because temperatures are easier to judge without unpredictable sunlight confusing things. His posture and facial expression are tense because he is about to roll the bones and either succeed in the most risky part of making a sword, or fail wasting weeks or months of work and thousands of dollars worth of materials. Notice how straight the glowing blade is.

A Japanese swordsmith with a blade poised for quenching Notice how straight the blade is. He has invested months of work into this blade to this point and a misjudgment or even bad luck in the next second can waste it all. Not a job for the inexperienced or timid.

Note that the formation of crystalline carbides in Japanese swords after heat treatment is densest nearest the hard cutting edge. The swordsmith therefore forges the blade straight before quenching it in expectation of it warping to the intended curvature when the crystalline structures at the cutting edge form, as seen in the photo below. This curvature is an intentional design feature that takes years of experience to achieve in a controlled manner.

Related image
After quenching, the warpage is dramatic. Notice the mud applied to the blade before quenching to control the formation of crystalline structures.

If the swordsmith intended to make a straight sword blade, he would have a forged a reverse curvature into the blade to compensate for the warpage that occurs during quenching. Plane and chisel blades exhibit similar but less dramatic behavior.

「折れず、曲がらず、よく切れる」を追求し、極限まで鍛え上げられた凛とした姿に、千年を超える日本刀の歴史と、生きることのすべての力を注いだ刀鍛冶の姿が浮かび上がる。
Both sides of a similar completed sword with the warpage an intentional design feature

The thinner the piece of steel being heat-treated, the more unpredictable the warpage and more likely the blade will develop fatal cracks. Within limits simple warpage can be corrected in thin blades, but not in stiffer chisels or plane blades. In the first few seconds after quenching and/or tempering a blade, the metal is still a bit malleable and warpage can be corrected to some degree by bending and twisting the still-hot blade. An experienced blacksmith will not rely solely on corrective measures but will anticipate warpage and create a curve or twist in the opposite direction when forging to compensate in advance of quenching. This takes skill and experience, and even then, some rejects are unavoidable.

Chemical alloys like chrome, molybdenum, and tungsten greatly reduce warping and the risk of cracking.

None of this is mystical, but tools made from plain high-carbon steels such as Aogami steel and especially Shirogami steel require more skill and experience than those possessed by factory workers, much less Chinese peasants, so mass-production is nearly impossible, labor costs are higher, profit margins are smaller, and advertising budgets are non-existent. No wonder such tools get little attention from the corporate shills in the woodworking press.

While modern chemistry has unveiled the mystery of steel, it has only been during the last 60 or 70 years that metallurgical techniques have been developed making it possible to understand and control steel manufacturing.

The manufacture and working of steel are still magical processes that are the foundation of modern civilization. Make no mistake: without steel and the skill to work it, human life on this planet would be short and brutal.

If you have good sharpening skills but haven’t yet tried chisel or plane blades made from Shirogami, Aogami or Asaab K-120 Swedish steel, you’re missing a treat.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the question form located immediately below.

Sharpening Part 6 – The Mystery of Steel

“The most beautiful experience we can have is the mysterious. It is the fundamental emotion that stands at the cradle of true art and true science.” 

Albert Einstein, The World as I See It

The blades we are considering in this series of posts about sharpening are made from iron and steel, so it makes sense to examine these materials from the viewpoints of sharpness and sharpening. Let’s look at some of the supernatural and legendary aspects of working steel first.

Steel Magic

Steel is a magical substance. Since ancient times, the blacksmiths that worked it were sometimes seen as gods, sometimes as wizards. Regardless of local traditions, the power blacksmiths possessed to combine and shape the elements of earth, wind, water, fire and even spirit into the tools and weapons of everyman’s trade was seen as magical.

Even the blacksmith’s forge and anvil were seen as magical in and of themselves, and rituals incorporating them were widely believed to keep evil at bay, provide good luck and blessings, and even to cure ailments.

There were several extremely famous magical blacksmiths back in the mists of time. Allow me to present two of them to you.

Vulcan the God

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Vulcan (aka Hephaestus), Roman god of fire and blacksmithing. Archaic relief from Herculaneum (National Archaeological Museum, Naples).

The bas-relief stone carving in the photo above is of Vulcan, the Roman god of fire and blacksmithing, also known as Hephaestus to the Greeks. This carving was excavated at Herculaneum, located in the shadow of Mount Vesuvius near Pompei. Herculaneum was an ancient Roman town destroyed by volcanic pyroclastic flows in 79 AD. The word “volcano” comes from the word Vulcan, so a stone carving of Vulcan retrieved from a town totally destroyed by Vulcan’s namesake is tragically ironic in the extreme.

Die Schmiede des Vulkan (The Forge of Vulcan) by Velázquez, Diego 1599–1660) Museo del Prado, Madrid, Spain.

The painting by Diego Velázquez above is from a scene in the Roman poet Ovid’s Metamorphoses where the god Apollo visits the god Vulcan in his forge to tell him that Venus, Vulcan’s wife, is being naughty with Mars, the god of war. Apollo is on the far left and can be recognized by his crown of laurel and shining aura. Vulcan stands next to Apollo with a shocked and incredulous expression on his less-than-beautiful face (nice abs, but his beard needs a lot of work). Vulcan’s assistants have stopped their work on armour (decidedly 15th century in style) astounded by both the sudden appearance of Apollo and the news he delivers.

Obviously, Venus and Vulcan were not a happy couple. Legend says that whenever Venus was unfaithful, Vulcan grew angry and beat hammer on anvil so fiercely that sparks and smoke rose up from the top of Mount Etna on the island of Sicily, under which he had built a forge, creating a volcanic eruption.

Perhaps Apollo is sharing this tidbit of news just to help out his old buddy Vulcan, or perhaps his reason for snitching is malicious. Whatever the reason, I think it’s safe to assume people loved drama in the 1600’s too. Nothing new under the sun.

My point is that Vulcan (Hephaestus) was not only worshipped in ancient Greece but had a presence in popular culture that ranged from before an Etruscan tribe drained the swamps that became Rome in the 10th century BC, to as late as the 1600’s. And I won’t even get into Trekkie lore. Now that’s an influential craftsman.

Wayland the Smith

Wayland the Smith (Vølund Smed) 1873 sculpture. Stockholm Sweden.

Wayland the Smith was another famous blacksmith, metalworker, and magician. He was said to be a Lord of the Elvish folk who learned his trade from either giants or dwarves.

While not as old as Vulcan in human history, Wayland’s legend survives throughout Europe, and the products of his forge were central to heroic traditions of many peoples and kingdoms since the days of the first Viking longboats.

He is credited in Norse, Germanic, and Anglo-saxon legends and literature with forging magical objects of great renown, including rings of power, the impenetrable coat of ring mail worn by Beowulf during his epic battle with Grendel, the magical sword named Gram that Sigurd used to slay the dragon Fafnir, and even King Arthur’s sword Excalibur. Not just scribblers, but even Alfred the Great, king of the Anglo-Saxons c.886~899 on the island that would later become England, wrote of him.

The chains on the legs of the statue above probably represent his maiming and imprisonment on an island at the pleasure of an evil Norse king upon whom he took a bizarre revenge involving unconventional drinking bowls and jewelry. Is Wayland’s slavery one of the reasons blacksmiths have wrapped chains around their anvils since ancient times, or is the purpose just to secure the anvil and mute the bright ringing sound they make? Another mystery…

Wayland’s influence in modern times is not insignificant. For example, Leonardo Da Vinci’s fascination with flying machines was probably stimulated by the legends of Wayland building and using a winged contraption to escape slavery. And unlike Daedalu’s deadly device in Greek legend, Wayland’s didn’t melt.

File:Gowy-icaro-prado.jpg
Daedalus (the bald guy) and his son Icarus (the falling guy) using wings to escape the island of Crete, home of labyrinths and monsters. Against his father’s advice, Icarus flew too near the son melting the wax securing the feathers that made the wings function. Oops.

The legends of Wayland the Smith were once deadly serious matters.

In a lighter vein, the writings of J.R.R. Tolkein, the author of the most popular works of written fiction in human history (no kidding), were influenced by these legends.

The Blacksmith’s Shop

While some blacksmithing traditions such as those involving Vulcan and Wayland are decidedly pagan in origin, others fit well with Christianity. For example, the ring of the blacksmith’s hammer on his anvil was once believed to strengthen the chains that bind the devil in hell barring him and his demons from God-fearing folk’s hearths. In darker times in human history the blacksmith’s workshop was believed by many to be a safe haven from evil forces, one that Satan and his imps actively avoided.

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The village smithy. Notice the horseshoe on the wall in the background, and its downward orientation. Due to the lack of char marks on the wall, we can tell this is not where the smith normally hangs horseshoes to cool. There is method to the madness.

Here is a link to a charming story about why blacksmiths ring their anvils and how to make sure a horseshoe brings you luck at work and at home. I encourage you to read it. Legend of the Ringing Anvil

The Japanese Smithy

If you have ever spent time in small one-man traditional smithies of the sort where our blacksmiths labor to produce the tools we carry then you know the other-worldly atmosphere typical of such workplaces. Imagine walls and exposed wooden roof beams blackened with 70+ decades of soot, the compacted but lumpy dirt floor, the darkness of carefully-managed sunlight (the better to judge metal temperatures by eye), the bitter smells of charcoal fumes, straw ash, flux, hot steel and burning oil; the roar of forced gas forges; the sounds of grinders and the antique leather belt systems that drive them; and finally the terrible racket and vibration of spring hammers and ringing anvils. A man that could work alone in a place like that 12 hours a day for 70 years is not afraid of your run-of-the-mill demon.

It’s quite a sight to see a craftsman working in such an environment. They often start late in the morning to avoid noise complaints from the neighbors, and work until late at night doing heat treating when sunlight won’t interfere with the colors of the hot metal.

By noon their arms are black to the elbows and charcoal smudges are on their faces. The sight of a small, wizened 82 year-old man with strong sinewy arms staring into yellow-hot steel as he hammers the hell out of it is a truly medieval scene. Something of the ancient magic of Vulcan and Wayland can be felt in such places.

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Mr. Junichi Takagi, Japan’s last adze blacksmith, passed away April 2, 2019. A kind man, talented blacksmith and excellent sharpener. He will be missed especially since he had no apprentices and no one will carry on his work.
Mr. Takagi working on his wet grinder in August 2018.

In the next post we will examine some alchemical aspects of the Mystery of Steel.

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YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the question form located immediately below.

Sharpening Part 5 – The Sharp Edge

The gem cannot be polished without friction, nor man perfected without trials.” 

Confucius

This post may not be as entertaining as my previous ones on the subject of sharpening Japanese woodworking tool blades: No swords or artwork or handsome Hollywood philosophers, I’m sorry to say. But with this post we will roll up our sleeves and dig into unartistic nitty gritty. I pray tender sensibilities are not offended. Many of my Gentle Readers already know most of what I will present in this post, but it is my fervent hope that one or two useful gems are hidden among the gritty.

You know the difference between the quality of work a sharp edge performs compared to that of a dull edge. Cuts are clean and finished surfaces are smooth, maybe even shimmering. Your tools are happy, singing and chirping as they cut away. But have you given thought to what a sharp edge really is?

Since the purpose of sharpening is to produce this condition in a blade, a clear understanding is useful. We will consider the basics in this post.

We shall also examine the naughty cutting edge that seems sharp but suddenly and unexpectedly dulls after just a little use. Would it be useful to know how to detect such a cutting edge before it fails wasting your time and money?

Let’s begin with bedrock basics.

The Basics

A cutting tool is essentially a wedge, with two flat sides meeting at an angle. Applying force causes it to sever materials, be it wood, metal, meat or mushrooms.

The geometry of this wedge is critical to its performance. At one extreme, the angle could be 90°. It won’t be sharp, it will be hard to push, and it will crush and tear wood instead of cutting it cleanly, but it will be durable.

At the other extreme, the wedge might be made more acute, say 3°. It could be extremely sharp indeed, but it would be too fragile to cut anything but whip cream for long. The point is that the sharp edge is a compromise, acute enough to cut well, but not so acute that cutting pressure and friction will make it dent, roll, wear away, crack or chip easily.

The effective blade must have a bevel angle that cuts the intended material well for a relatively long time. The words “well” and “long” in the previous sentence are where the magic lies. We will examine these important points in future posts in this series.

Germ’s Eye View

The extreme edge of the ideal metal tool’s extreme cutting should be perfectly smooth and only a single molecule thick. In the real world, cutting edges are rougher and wider, but still manage to cut pretty well.

Examine a sharp cutting edge under a microscope, and you will see imperfections. A dull blade will look even worse of course, showing dents, rips, and even cracks. 

knife edge_microscope800
The edge created by an 800 grit stone
Still sharp but starting to wear
A dulled and dented knife blade

Using a blade wears away and damages the cutting edge rounding and flattening it, destroying the geometry that makes it an effective wedge. Sharpening is the process of (1) restoring the intended wedge geometry; and (2) removing defects from the meeting of the wedge’s sides by abrading metal from one or both sides down past any damage, leaving a relatively clean, uniform wedge with minimal defects. This is the sharp edge. It is what the wood experiences. It requires effort to achieve, but it ain’t rocket surgery.

The most difficult part of achieving the two objectives listed above is making nothing from something, in a place that cannot be seen. Now that’s a Zen koan.

Building confidence in one’s ability to achieve results at the microscopic level is not easy. The key is to understand the goal, and to consistently follow reliable procedures. I will describe those goals and procedures in future posts in this series.

Edge Failure

The ideal cutting edge is uniformly sharp, but few edges in the real world meet these severe criteria at the microscopic level where it matters most. A blade may be sharp in some places, and dull in others. Likewise, a blade may cut well for a while and then dull quickly and suddenly. We have all experienced these irritating failures.

One common cause of these inconsistencies and failures is that the edge is sharp only because it has a defect called a burr. Burrs by themselves can be sharp indeed, but they are fragile and can bend, roll over, or break off at the root suddenly and unpredictably creating a nasty dull edge in an instant. A truly sharp edge will not just feel sharp, but will stay sharp for a relatively long time because it is properly shaped and well supported, instead of being only temporarily sharp because of an irregular and fragile burr.

I call burrs a “defect” because they are, but creating a burr is an important step in making a sharp edge. The trick is to continue to refine the wedge after the burr is created until it is gone and the edge is as perfect as we can reasonably expect to make it. Stop the refinement work too soon, or fail to do it completely, and all or part of that unreliable burr may survive to cause trouble.

So how does one tell if an edge is properly sharp and free of deceptive burrs without using a scanning electron microscope?

Do you remember ‘Nando’s philosophy described in my previous post? One must use reverse logic from our latin lover. Don’t rely on mahvelous appearance. Don’t rely on bar room tricks like shaving arm hair or cutting strips of paper. Develop skills and train your senses other than eyesight to detect the shape of steel at the microscopic level. This may sound strange but it is possible because your nerve endings are microscopic and can sense the difference between a burr and a truly sharp edge.

I will save the explanation of detailed techniques for a future post, but for now, here are two essential skills: Use your fingerprints to detect the presence and size of burrs. Use you fingernails to check the condition of the burr and determine when the blade is ready to move onto the next stone in the sharpening process. Please don’t cut yourself.

In the meantime, let’s have some pleasure before pain. Prepare to be amazed, Ladies and Germs, because in Part 6, coming soon, The Mystery of Steel will unfold before your very eyes! There will be marble relief carvings, bronze statues, oil paintings, gods and demons, death and destruction, and even a pagan soap opera about forbidden love. Oh my! We’re in negotiations for the movie rights now ♫꒰・‿・๑꒱ and need someone to play Vulcan. If anyone knows Spiderman’s agent, please have his people contact my people right away.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the question form located immediately below.

Sharpening Part 4 – ‘Nando and the Sword Sharpener

And this is from my heart
Which is deep inside my body:
It’s better to look good
Than to feel good

Fernando

This post is a little longer and more roundabout than my previous posts, but I wanted to share with you some of Japan’s history, and examples of this country’s most fabulous art as produced by its blacksmiths and professional sharpeners. But before I get into that, I would like to share some relevant words of wisdom from Hollywood’s wisest man.

Billy Crystal in Fernando’s Hideaway

The handsome gentleman in the picture is Fernando. He is neither a blacksmith nor a sharpener of tools or weapons, but his insight into physical beauty and words of wisdom about happiness are pertinant to sharpening, as we shall see below. If you are not familiar with ‘Nando, I suggest you google him or view a video or two on Youtube.

So what does our dapper Latin Lover have to do with sharpening? And swords?

As ‘Nando taught the world, a wise person will not equate looking good with feeling good. Likewise, you would be wise to not confuse a blade’s appearance with its performance. Indeed, a blade that looks as sharp as the skinny end of nothing may not actually cut very well in some applications.  A good example is Japanese swords. Let me tell you a true story to illustrate my point.

When I was a University student in Japan, I was privileged to be entrusted with a number of swords that belonged at the time to the late Dr. Walter Compton, Chairman of Miles Laboratories and the inventor of Alka-Seltzer. He was a wealthy man who had a huge collection of swords obtained while an officer for the US military in Japan immediately after the war when Allied forces required the defeated Japanese people, on pain of death, to surrender all swords, civilian and military. Of course, many valuable and rare family heirlooms were surrendered or forcefully confiscated. Supposedly they all went to the bottom of Tokyo Bay in bunches, or were melted for scrap. But we know better, don’t we.

Towards the end of his life, Dr.Compton put a lot of money into having his better swords professionally sharpened, new shirasaya scabbards and furniture made, and formally evaluated in preparation for donating them to the Boston Museum of Art, where many of them reside today. Sadly, some were auctioned off without his permission. “The feckless sons of wealthy men” is the operative phrase in this case, I fear.

I assisted Dr. Compton’s representative by transporting over 70 of these swords to and from Japan and performing the necessary legwork to accomplish these goals inside Japan. During those years I held in my hands and feasted my eyes on rare and beautiful blades of great historical value several of which would have easily been designated National Treasures if they had been intended to remain in Japan (“National Treasures” may not leave Japan). 

During those years I spent a lot of time meeting, questioning, and requesting services of the best sword sharpeners in Japan, and learned a lot about swords, stones, and sharpening. Dr. Compton’s reputation was such, and his swords were of such rarity and high quality that I had no difficulty persuading the very best craftsmen to work on them or speak with me including Mr. Okisato Fujishiro.

Interestingly, in Japan such craftsmen are called “Togishi” (研師), an unambiguous word that can only be translated as “sharpener.” However, in the West these same Japanese craftsmen are called “ Sword Polishers.” In the post-war context, this actually may be more accurate than the Japanese term.

A very subtle, high quality sword tip brought to life by the arts of the Sword Sharpener. Notice the peaceful elegant hamon (wavy milky pattern at the cutting edge oriented towards the top of the photograph), the grain of the steel just below the hamon, and the burnished polish surrounding the fuller. Notice also the clean delineation where the blade tip, the “boshi,” begins. Very nice work.

Traditional Japanese society before the elimination of the caste system had 4 main divisions labeled  “Shi No Ko Sho,” meaning, in descending order, Warrior (samurai) Farmer, Craftsman, and Merchant at the bottom. The Emperor, Court Nobles, and Shoguns were above these strata, although only the Shogun possessed any actual power of the three. The man with the sword makes the rules, and those without weapons do what they are told or die. Such it has always been.

Blacksmiths and sword sharpeners were both in the craftsman caste, but the sword sharpener was above the swordsmith in rank. Depending on their support among the warrior caste, and with the generous application of yellow metallic lubricant, both swordsmiths and sword sharpeners occasionally obtained noble rank, an honor to which most other craftsmen, farmers, and merchants could not aspire My point is that sword sharpeners, while of low caste, often had a perceived rank higher than their craftsman position would suggest.

Why was the Japanese sword sharpener of higher rank than the swordsmith? I haven’t seen documentation from back in the day confirming it, but I suspect it is because the sharpener turns the swordsmith’s plain steel blade into a thing of jewel-like sculptural beauty that almost seems alive. One only has to see a sword blade fresh from the blacksmith’s shop and compare it with the same sword after the sword sharpener’s ministrations to understand.

The Nikko Sukezane sword, a designated National Treasure of Japan
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This sword is known as the “Nikko Sukezane,” Nikko for the temple commemorating the Shogun Tokugawa Ieyasu (徳川家康, January 31, 1543 – June 1, 1616) where it is stored, and Sukezane (助真 meaning “Aid the Truth) for the name of the smith who forged it for the Kamakura Shogunate (1185~1333). The blade’s shape and crystalline pattern above the hamon are characteristic of Sukezane’s work. This sword’s brother was in my care for about 2 years while it was being polished and appraised in Tokyo.
大般若長光-画像2
This sword is another of Japan’s National Treasures. It was forged by a swordsmith name Nagamitsu (長光)during the same time period as the Sukezane above. The tang (nakago) is corroded by exposure to bare hands over a period of around 700 years. Multiple holes were drilled in the tang to accomodate different kinds of hilts during its lifetime. I also had a sword by this same smith and of very similar appearance in my care for about one year, although it was not owned by Dr. Compton.
A different Nagamitsu sword, also listed as a National Treasure. An unusually healthy example.

I have even witnessed a skilled sword sharpener create a beautiful hamon (a pattern formed on the edge of a sword by the steel’s crystalline structure) on a sword forged by a famous smith that had lost the crystalline structure necessary to form an actual hamon. While a deception of sorts, the intention was not to deceive for profit (the sword was donated to a museum), but to return an unusual and historically important sword to its former beautify, a glory that would have been lost but for this sword polisher’s exceptional skills.

A dramatic chouji midare hamon in a modern sword. The pattern exists because of the changing crystaline structure of the blade that results from the differential heat treatment process performed by the blacksmith, but it is only visible and beautiful because of the sword sharpener’s stones and his skill with them. Is the blade sharp? Don’t judge a blade’s performance by its polish.

If we liken the swordsmith with his forge and hammer to the quarry worker cutting marble from the mountain, then the sword sharpener is Michelangelo cutting the Pietà with his chisels and files. Both craftsmen work on the marble and blade respectively, and both are essential. The sculptor uses steel to bring stone to life, while the sword sharpener uses stone to bring steel to life.

chojimidare.jpg
Another dramatic hamon in a modern sword.

But despite these artistic abilities, modern “Sword Polishers” have no interest in and make no effort to actually make a sword blade cut well. Indeed, in some cases, they actually intentionally dull the blade so it can’t cut, thereby making it safer. This intentional vandalism is called “habiki.”

A different style of hamon pattern on a blade with a different grain pattern. Notice the different colors and lines inside the hamon. All these tiny details have names, are categorized and studied intensely by aficionados. All things equal, this sort of pattern and color is considered to be more elegant and desirable than the two more dramatic hamon pictured above. An extremely deep rabbit hole, I assure you.

Here is the key point I want you to understand: Despite the long years of apprenticeship, advanced skills learned, and gallons of blood unintentionally leaked by sword sharpeners, the frank sword sharpeners I have spoken with all admitted that, of all the craftsmen in Japan that used edged tools, woodworkers like carpenters, cabinetmakers, and joiners routinely create sharper blades despite those blades not appearing as sharp as swords. This is consistent with my direct experience of handling over 70 swords before and after being worked on by sword sharpeners.

While there is great pleasure to be found in polishing a plane or chisel or knife blade to levels of great beauty, do not make the mistake of equating appearance with performance.

Appearance aside, and looking strictly at cutting performance, will a chisel or plane or knife blade skillfully sharpened on a 15,000 grit stone cut better and longer than if sharpened on an 8,000 grit stone? In the case of woodworking blades and kitchen knives, no it won’t. In fact, due to higher levels of friction in the cut, it will certainly not cut wood as well. More on this subject later.

Hidarino Ichihiro Oiirenomi. The hazy silver of the hard steel hagane lamination and the cloudy grey of the softer iron jigane lamination, combined with the shape and upward curvature of the corners of the lamination are indicative of unexcelled craftsmanship by the blacksmith, superior skills of the sharpener, and excellent stones. Such details are considered sublimely beautiful to tool connoisseurs. But will the edge cut well? We can’t tell from this photo.

Keep in mind that the stones used to apply the beautiful polish and accentuate the hamon on Japanese swords are different from those used to sharpen woodworking tools. For instance, the uchigumori stones sword polishers use are small slices of very soft stone glued to paper using urushi lacquer, and are only 3,000~5,000 grit. These small slips of stone are rubbed on the sword blade using thumb and fingertips.

Here is a link to a blog showing Mr. Fujishiro, son of one of the sword sharpeners I employed back in the day, making and using these thin slices of stone.

Tools are designed to perform specific tasks. Although it could do the job, more or less, you wouldn’t use a crescent wrench to stir spaghetti sauce on the stovetop would you? A longish spoon just might work better. Does a sword’s edge need to be extremely sharp to cut the enemy effectively? No, it doesn’t because the sword’s speed, impact force, and swordman’s technique influence its cutting effectiveness much more than sharpness. So sword sharpeners have always been more focused on edge durability, resistance to chipping, and appearance than absolute sharpness. In modern times, when swords are almost never used to cut living flesh outside of Saudi Arabia, the blade’s appearance may be critical, but sharpness is not a practical concern.

Another example is food preparation knives. A chef’s knife looks terribly sharp, and as it slices tomatoes and fillets fish we can see that it cuts well. But how sharp is it really? In comparison with a joiner’s plane blade, not really that sharp. But both tools are exactly suited to the job assigned them.

柳刃包丁(刺身包丁)
The sashimi knife is made long to facilitate long draw-strokes that cut the fish cleanly. The chef applies little downward pressure which would rupture the cells ruining the flavor of the tuna sashimi. Yes, a properly sharpened knife and expert technique make a difference in flavor, just another reason why the Japanese are obsessed with sharp things.

The chef’s knife is most effectively used in slicing or drawing motions, much as expert swordsmen use their weapons against enemies. In this style of cut, a smooth and uniform cutting edge does not perform as well as a more ragged, serrated edge as seen at the microscopic level. Therefore, there is little if any practical benefit (assuming beauty is not practical) to be obtained by sharpening a kitchen knife beyond 1,000 or 2,000 grit. In fact, at least in Japan, these are the upper-limit of stones in daily use by professional chefs of all varieties. Yes, and that includes sushi chefs.

But don’t misunderstand my point: In the case of both swords and yanagiba hocho knives, the bevel angle must be correct for both the blade being used and the material being cut, and the microscopic edge must be a clean intersection of planes. If you get these two factors wrong, a crescent wrench might work just as well.

The other point I want to make is that, while I enjoy using high-level skills to create a very sharp blade with a beautiful appearance, such a blade will not perform better than an identical blade of equal sharpness but with a less polished appearance, and the extra time and money spent on improving outward appearance is wasted on bread and butter work. 

Since Hollywood celebrities have the answers to all the world’s problems (at the cost of other people’s money, labor and freedom, of course) perhaps our quest for the sharp edge can benefit from the wisdom of the famous Latin lover ‘Nando, Tinseltown’s most elegant star. ‘Nando once shared his father’s advice that it is “better to look good than to feel good.” Accordingly, perhaps we should all go crazy nuts and polish our blades like beautiful but dull museum swords and wear waistcoats and cravats as we cut sliding dovetails and plane door stiles. After all, one must be ready for every photo op. In this way, our woodworking blades may be worthy of ‘Nando’s highest praise: “You, dahling, you look mahvelous, absolutely mahvelous.”

Fernando Lamas in “The Merry Widow.” The crease in his pant leg could slice bacon.

No, on second thought, while there is much one can learn from Fernando’s elegant philosophy, his standards of beauty and suffering are too high for me. I would rather be a simple joiner or cabinetmaker in stained work clothes that has the ability to make a blade exceptionally beautiful but chooses not to expend the time and cost required to do so most of the time, rather than someone who doesn’t because they can’t.

Although Fernando has a pressing appointment for a tango lesson he must give (discretion prevents me from naming the young lady he is pressing) and won’t be providing further insight, our adventures in sharpening Japanese woodworking tools will continue in Part 5 of this series.

Let’s meet at Tsukiji for sushi afterwards.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the question form located immediately below.

Sharpening Part 3 – Philosophy

A wild boar was sharpening his tusks upon the trunk of a tree in the forest when a fox came by and asked, Why are you doing that, pray? The huntsmen are not out today and there are no other dangers at hand that I can see. True, my friend, replied the Boar, but the instant my life is in danger, I shall need to use my tusks. There will be no time to sharpen them then.”

Aesop (621~565 BC)
Always ready for battle

It’s nice to have a philosophy on a subject because it helps one distill random thoughts down to the essentials.

Allow me to explain my philosophy about sharpening woodworking tools, not because it is charming and unique, and not because you should emulate it, but because it will provide insight into the things I have written and will write about sharpening on this blog and elsewhere. Use it to calibrate your BS meter. It is often neck-deep when people talk about sharpening stuff.

My philosophy regarding sharpening was shaped by my experience as a carpenter, contractor, commercial cabinetmaker, and joiner working under pressure, against a clock, sometimes with a boss watching with eagle eye, and often in front of customers, not as a hobbyist fiddling around in a garage workshop. Married young with a growing family to support, I quickly discovered that children eat constantly and in ever-increasing quantities, so efficiency was and is important to me. 

Efficiency was also important to the Clients who hired me. Sharpening and maintaining tools was indeed part of the job, but from the Client’s viewpoint, it was wasted time, so it was important to minimize time spent fiddling with tools during the work day. I followed the example of craftsmen I respected and started the day with sharp tools in good working order, and kept spare planes and chisels sharpened and ready to go as backup.

Self-employment hammered into me the monetary value of time. It also taught me quality sharpening stones and tools are expensive and wear out, and that to feed wife and babies every day I had to work efficiently to minimize time and money expended on maintaining tools, while maximizing the amount of work I accomplished between sharpening sessions. 

I developed a strong dislike, nay hatred, for blades that fail, dull quickly, or take too much time and effort to sharpen. I loathe them not just because they are irritating, but because they waste my time and money. Even considering the higher initial cash outlay, the cost-effectiveness of handmade, professional-grade tools in helping my mind and hands feed the family became as obvious as a burning road flare on a midnight highway.

You, Gentle Reader, may not feel the time and financial pressures that professionals do, but learning how to sharpen your tools more efficiently will make woodworking less frustrating, more profitable, and more enjoyable.

What is your philosophy?

Sharpening a chisel at the jobsite, then back to work, jiggety-jog.

The journey will continue in Part 4 with wisdom from a celebrity and pictures of pretty swords.

YMHOS

Links to Other Posts in the “Sharpening” Series

Sharpening Japanese Woodworking Tools Part 1

Sharpening Part 2 – The Journey

Sharpening Part 3 – Philosophy

Sharpening Part 4 – ‘Nando and the Sword Sharpener

Sharpening Part 5 – The Sharp Edge

Sharpening Part 6 – The Mystery of Steel

Sharpening Part 7 – The Alchemy of Hard Steel 鋼

Sharpening Part 8 – Soft Iron 地金

Sharpening Part 9 – Hard Steel & Soft Iron 鍛接

Sharpening Part 10 – The Ura 浦

Sharpening Part 11 – Supernatural Bevel Angles

Sharpening Part 12 – Skewampus Blades, Curved Cutting Edges, and Monkeyshines

Sharpening Part 13 – Nitty Gritty

Sharpening Part 14 – Natural Sharpening Stones

Sharpening Part 15 – The Most Important Stone

Sharpening Part 16 – Pixie Dust

Sharpening Part 17 – Gear

Sharpening Part 18 – The Nagura Stone

Sharpening Part 19 – Maintaining Sharpening Stones

Sharpening Part 20 – Flattening and Polishing the Ura

Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the question form located immediately below.