Sharpening Part 14 – Natural Sharpening Stones

Advice is a dangerous gift, even from the wise to the wise, and all courses may run ill.

J.R.R. Tolkien
The finest, softest natural stone I routinely use. Black Cashew Urethane paint for protection.

We receive a lot of enquiries about natural finishing stones, so I wanted to share some of my thoughts and experiences about them with you. Perhaps they will be useful.

To begin with, natural Japanese stones are a lot of fun, and can create a beautiful, cloudy finish on a blade’s bevel. They make my heart sing, wild thing.

I think blades finished with a natural stone tend to stay sharper a little longer compared to synthetic stones, but can’t prove it. Despite my fondness for them, I want to make it clear that natural stones are not magic, and are not critical to do good work.

It is interesting to note, however, that while top-quality natural stones are expensive, if judged by the amount of steel they can sharpen, they are actually no more costly than the better synthetic stones. But they can be more of a gamble.

Geologists believe that Japanese natural sharpening stones were created when particles of volcanic dust fell from the sky, transported, sorted, and sifted by winds and waves, and settled onto the sea floor eventually becoming sedimentary stone.

Being natural, they carry the inherent and potentially expensive risk of internal defects, such as weakness between sedimentation layers, cracks, and contamination such as hard particles of sand concealed inside. Even if you find one that seems perfect in every way, the bones never stop rolling because you never know what lurks inside.

Medium hardness natural finishing stone I regularly use.
The stone is epoxied to a base made of Ipe wood. The sides are coated with a natural urethane called Cashew, a product of the cashew nut tree, to prevent water from soaking into the stone’s sides potentially causing cracks and separation. The bright orange color is to ensure pesky pixies do not talk the stone into sprouting legs and walking away when outside the workshop.

I erred with my first purchase of a natural stone. It was recommended by the hardware store owner in Sendai where I bought it many years ago, and I fear he intentionally foisted a low-quality stone on me that a person more experienced with natural sharpening stones would have rejected. This stone “drags” steel, a phenomenon where the stone deposits hard clumps on the blade that gouge the stone’s surface and leaves rough spots on the blade. It’s impossible, BTW, to judge a stone’s propensity for this pixieish behavior by eyeball alone. I learned an expensive lesson about both natural stones and salesmen that day. I still use that stone for sharpening axes and gardening tools, but the real reason I keep it around is as a reminder of my foolishness.

After that first disastrous purchase, I became more careful and paid less attention to what people said or write. Instead I learned from people’s mistakes. And I considered motives. Consequently, I don’t give a rodent’s ruddy fundament about most people’s opinions. Too many who claim expertise talk and write about things they only partially understand. Many have a conflict of interest. Still others seek justification of their poor decisions.

Nor I do care about the region or mountain or mine a stone came from, or its designation or color. Even the best mine produces mostly waste.

And because of the impossibility of evaluating stones long-distance, and considering Gildor’s wise words quoted at the top of this post, I don’t give advice about stones, so please don’t ask. But I will tell you what I do when buying a stone:

  1. I examine the stone for cracks and signs of irregularities and impending separation at its sides (not all defects are fatal);
  2. I take the stone in my hand, close my eyes, and feel it;
  3. I flip it with my fingertips and listen to the sound it makes;
  4. I touch it to my teeth (the surest way to detect the fineness and consistency of a stone’s abrasive qualities);
  5. I put a plane blade to the stone and take a few strokes, and like a bow on violin strings I feel the friction and listen to the music;
  6. I examine the scratches it leaves on the blade’s jigane and hagane using a loupe. 

None of these critical tests can be conducted long-distance. BTW, if you think any of them are pointless, then I know where you can get a good deal on some swamp land in North Korea.

I have two natural stones I use regularly nowadays. One is of medium hardness suitable for most every straight blade. The other (see the picture below) is very soft, and easily damaged, but creates a beautiful foggy finish on the steel. 

I love my natural finishing stones, the feel of using them, the smell, and the pretty finish they produce on my blades. They are part of the romance unique to Japanese blades. I believe the stones I use now and their sisters worn to slivers in past decades were worth every penny I paid for them, but I recognize this is an emotional rather than practical viewpoint, and difficult to defend economically.

And just to save you wasting your time with questions, allow me to explain that we don’t sell synthetic sharpening stones because we can’t sell enough to justify procuring enough volume make our prices competitive. Besides, shipping costs would be too high. And we don’t sell natural stones because we cannot provide a warranty on anything so unpredictable, and I really hate disappointing people.

Don’t misunderstand: I am not suggesting you should not try natural sharpening stones, only that you carefully evaluate them in-person beforehand, and buy from a reputable dealer that offers a reliable warranty (please don’t ask for recommendations). And just to prove I am neither troll nor curmudgeon, I will give you the same four points of sound advice about purchasing natural sharpening stones that a wise old man gave me a long time ago, advice that has passed Gildor’s test.

  • First, don’t trust your eyes alone when judging a stone’s origin, designation, appearance, or performance (see the five tests listed above);
  • Second, don’t buy a stone from someone you don’t trust and who won’t give you a reliable 30 day warranty. That gives you time to check the stone carefully for suitability and defects. Remember, the combination of stone and blade is much like a marriage where the softer (but actually granularly harder) stone smooths and polishes the harder blade. If the two don’t work well together, then even lawyers can’t make it right, but a warranty may help reduce the damage;
  • Third, always try a blade on the stone before purchasing it to make sure it works for you and your blade;
  • And fourth, don’t whine if the stone disappoints: roll the dice and smile at the faces they show you. Besides, hoes, axes, and hedge shears need sharpening love too.

On the other hand, if you can follow the last rule and don’t mind risking your money, then the previous 3 rules can perhaps be ignored. I grew up in Sin City and know that can be fun too. You pays your money and you takes your chances. Viva Las Vegas!

Ancient Roman or Norse dice in a pose worthy of gambling.

YMHOS

© 2019 Stanley Covington All Rights Reserved

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.

The Story of C&S Tools

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A Kiyotada 24mm atsunomi, the first truly professional-grade chisel I purchased over 33 years ago. It’s an elegant tool with awesome performance. I got it at a discount because of some cosmetic defects I polished out, which is why the finish is bright and the neck is slightly rusted.

“End? No, the journey doesn’t end here. Death is just another path, one that we all must take. The grey rain-curtain of this world rolls back, and all turns to silver glass, and then you see it. White shores, and beyond, a far green country under a swift sunrise.”

J.R.R. Tolkien, The Lord of the Rings”

The story of C&S Tools is not one of a business looking for products to sell, or of a manufacturer looking for buyers, but of craftsmen looking for better tools.

I have lived and worked in Japan for many years, and learned about Japanese woodworking and Japanese tools from serious professional craftsmen called “shokunin.” They included primarily carpenters and joiners, gentlemen that were obsessed with the performance of their tools. They influenced me to seek out the best handmade woodworking tools available, including chisels, planes and saws because better tools help one work more productively while making the job more pleasant. I am still absolutely convinced that is true.

I bought many different brands of tools back in the 8o’s and tested them. I asked craftsmen who’s skill and work impressed me what brands of chisels and planes and saws they used. After years of trying various brands, in the end, I concluded that Kiyotada and Ichihiro made the best chisels and Yokozaka Masato made the best plane blades available at the time. Over the next ten years, I disposed of my other chisels and planes and built up sets of chisels and planes by these blacksmiths.

My work has required me to move many times. In 2009 I was transferred back to Tokyo from Southern California, but the moving company mistakenly placed all of my chisels and planes in storage in the US instead of shipping them to Tokyo, so for several years I did not have access to them.

I no longer use my tools to feed the family, but still enjoy woodworking as both hobby and therapy to help maintain my sanity, so life in Tokyo without my tools was lacking something important. I tried to purchase a few of my favorite tools by Kiyotada, Ichihiro, and Yokozaka but found they were no longer available, and because of the Kezuroukai effect, even used ones had doubled in price. Only Yokozaka-san was still alive, but once again, the Kezuroukai effect resulted in long waiting lists and inflated prices for his planes. I eventually purchased a 10pc set of oiirenomi chisels from a retailer I trusted under the brandname Kiyohisa because, while the retailer warned that Kiyohisa’s products were nowhere near as good as Kiyotada or Ichihiro, he insisted that the Kiyohisa brand was as good as it gets anymore. They were fairly expensive.

Sadly, the Kiyohisa chisels were not only inferior to Kiyotada’s products, but of poor quality even when compared to cheapo tools, with some blades chipping unduly, others rolling their edges, and still others with poorly-performing differentially-hardened cutting edges. Absolutely hopeless. I took them back to the retailer and demanded a refund, but he responded that Kiyohisa products did not have a warranty. I since learned that this blacksmith does not warrant any of this products. As you can imagine I lost faith in that retailer’s opinion and the products they sell. You can probably imagine my opinion of Kiyohisa too, so I won’t inflict you with the rant.

At this point I started buying many different famous brandname chisels and tested them to destruction. The standard against which I compared them all was the excellent Kiyotada products forged by Shimamura Kosaburo, a blacksmith who was at one time lauded by metallurgists as being the best chisel blacksmith in Japan. I have yet to find a better chisel, but I tried. The testing criteria were initial sharpness, durability (resistance to cracking and chipping) and edge retention ability.

The testing process I employed was to sharpen each 24mm chisel’s blade to 10,000 grit, and cut mortises with it in a Japanese hardwood called Keyaki (zelkova wood). I would abuse each chisel to determine how tough it was, and examine the edge after cutting each mortise. If the edge rolled or dented (and many did), then I knew it was too soft and rejected it. But if it chipped, broke, or performed well, I took it to the next step where I re-sharpened it and continued to cut mortises until the edge chipped or dulled. I rejected those chisels that readily chipped or quickly dulled. Most of the newly-produced chisels sold under famous brand names, and all the chisels produced in Miki, which were too soft, failed these comparative tests utterly.

It was an expensive process but I learned an important lesson, namely, that brandname has nothing to do with quality or performance; The true source of quality and performance in edged tools is rather the blacksmith himself, his experience, skill, and rock-solid dedication to quality. Sadly, this common-sense logic is not applicable to mass-produced products. The key point is that most “brandnames” are sold by wholesalers and retailers to “markets” that have no direct voice, whereas blacksmiths sell to “customers” that give them direct feedback. Accordingly, the quality and performance of a blacksmith’s products directly impact his personal reputation and self-respect, as illustrated by the example mentioned above, whereas most wholesalers and retailers have little at stake.

If a tool wholesaler’s primary market is amateurs located in far-flung countries outside of Japan, then appearance and a reputation of his brandnames, inflated by marketing, have much greater influence on his profits than blade quality. Indeed, few amateurs in any country know how to properly use and maintain professional-grade chisels. Even in Japan, amateurs carelessly damage blades blaming their failure on the blacksmith and making it a warranty problem for the wholesaler and retailer. Therefore, when marketing exclusively to inexperienced amateurs either domestically or internationally, the wholesaler’s surest path to profitability is to sell mass-produced blades that are softer and more resistant to damage than blades intended exclusively for professional woodworkers. Blades sold primarily to amateurs overseas do not need to be hand-forged from the best materials but can be mass-produced using less-expensive steel at lower cost resulting in higher profits. That is the Miki way of doing business, very much in the style of MacDonalds. Do you like kangaroo meat?

I had learned an expensive lesson, and so putting it to good use, I next went looking for real live blacksmiths instead of famous names. I focused on traditional blacksmiths unaffiliated with the large wholesalers, working in small smithies who continued to produce chisels and planes for professionals using traditional blacksmithing techniques, and did not stoop to mass-production. I had set myself a time consuming challenge that couldn’t be accomplished using the internet or telephone alone. I bought more chisels and damaged more blades. I spent weekends on trains going all over Japan visiting woodworkers and blacksmiths, inspecting forges, and checking QC techniques and steel stockpiles. At last I found 3 chisel blacksmiths and one plane blacksmith that consistently produced only the professional-grade tools I wanted with real-world performance approaching that of Kiyotada, Ichihiro, and Yokozaka.

I should add that Kiyotada, Ichihiro, and Yokozaka’s tools were expensive even when they were alive and producing daily. But since the tools I was seeking were to be secondary, perhaps temporary tools, I was willing to sacrifice appearance for lower cost on condition that the tools satisfied my performance goals. The blacksmiths I found did not make the prettiest blades, but they all cut like crazy and kept cutting a long time without dulling or chipping.

During this process I was in communication with professional woodworker friends in the US that know how to use and maintain Japanese planes and chisels. I told them of my adventures and even sent them some of the tools I found to try. After testing the tools they too wanted some. Word of mouth spread and one thing lead to another.

I have a day job, so C&S Tools is not focused on maximizing profits. We sell our tools for the standard retail price in Japan plus PayPal fees of 4.1%, without a gaijin or export markup. It’s more of an excuse for me to spend time with the Japanese blacksmiths and other honest craftsmen I respect.

Unfortunately, our blacksmiths are not getting younger. All are in their late 70’s and 80’s. Production will not continue much longer, so if you are looking for professional-grade chisels and planes at a reasonable price, as I was, then don’t wait too long. No one knows when the “grey rain-curtain of this world will roll back and all will turn to silver glass,” as the old wizard put it.

Stan Covington

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A 24mm Sukemaru brand atsunomi

PS: If you have questions or would like to learn how to purchase our tools, please use the questions form below and we will respond.

The Varieties of Japanese Chisels Part 15 – Ootsuki Nomi 大突き鑿

All times are good for those who know how to work and have the tools to do so.

Carlos Slim

The Ootsuki nomi is the largest of the Japanese chisels. It is essentially a scaled-up tsukinomi paring chisel, equivalent to what is called a “slick” in the West.

Definitions

The name is written 大突鑿 which is the same as tsukinomi with the addition of the character 大 meaning “large,” or “ big.” Besides “Oo “ this character can also be pronounced “dai.” If you examine this very basic Chinese character you may notice it looks like a man with his legs spread and arms extended, as if he is describing to his buddies the size of the fish that got away. At least that’s how I remembered the meaning when I was a young man in Japan many moons ago.

So the name translates directly to “large paring chisel.”

Applications

If you have never done timber framing, a brief explanation may be helpful. 

When doing production work (versus hobby stuff) one cuts the pieces and parts of most open joints using circular saws. Handsaws are also necessary for some cuts, but for most situations a circular saw is much quicker and less tiring. There’s a lot of wood that needs cutting after all and only so many hours of daylight.

Mortises are typically cut with portable electric hollow-chisel machines. There are other options such as portable chainsaw mortisers, stationary router machines, or the amazing German Hundegger machines. http://hundeggerusa.com

I once worked for a Japanese company that cut entire structural frames using CAD driven CNC machines in a factory. In that situation however, the CNC machinary, while very precise and very quick, was so expensive and so inflexible that the building had to be designed around the repertoire of joints and sizes the machinary could cut rather than the joints required to make the best building. And it could not handle significant dimensional irregularities in the timbers used, so only machined glulams were suitable. A very limiting endeavor indeed. The sort of frame the gentlemen in the pictures below are cutting was simply impossible for CNC equipmennt. I left that job after 2 years.

Sharp tools guided by human hands, controlled by human minds with years of experience are more flexible.

Paring a saddle
Paring a splice joint with a 48mm chisel
Paring a notch where two beams will cross over and under
Paring a large through-tenon

Indeed, handtools like axes, adzes, chisels and handsaws are necessary especially when doing “ round work” in logs or when the design calls for irregular-shaped timbers. Paring chisels are also needed to achieve the relatively precise tolerances and smooth surfaces such work demands.

Ootsuki nomi are relatively heavier than other Japanese paring chisel with larger diameter and longer handles. They are  built to resist the large bending moment forces created by a large man gripping the handle with both hands and pushing like a plow horse to pare wood. This is the task this chisel excels at.

Most Japanese carpenters that use this tool buy them in sets of two: a wide 48~54mm wide one and a narrower 24mm chisel, although other sizes are available. I own a set by Kiyotada, one with a 54mm blade and an extra-large handle intended for working especially large North American  timbers. 

The wider width of the two in the set is used most frequently for paring tenons and saddles. 

The 24mm is used for paring standard rectangular mortise, dovetail mortises and dovetail tenons, besides a hundred other tasks. In cross section, it is essentially a large shinogi usunomi chisel to help it get into tight places.

Paring the end walls of a mortise with a 24mm chisel

Mitsuura

When paring large surfaces with the wider ootuskinomi chisel the hollow ground ura may allow bumps to escape paring requiring multiple passes to knock them down. This is easy to overcome with practice, but some people prefer an ura with not a single, but multiple grinds with lands between each hollow-ground area to help index the blade. I believe this is one of the few situations where these multiple ura, called mistuura or “triple-ura” are useful.

Kensaki Ura by Sukemaru. A very unique style of mitsuura. Pretty cool, huh. Sadly, Mr. Usui no l0nger does this detail no many how hard I beg.

Some people like the unusual appearance of mitsuura. I must admit they look sexy in wide blades, but they have their downsides . The first downside is that mitsuura blades can take a little longer to sharpen. Second, they can be a little harder to keep flat. Neither of these are difficult problems to overcome. But the third downside is more problematic. 

A worn-out mitsuura oiirenomi

Because the three hollow-ground areas are shallower and have less total volume than a single ura, they tend to wear out and disappear sooner. This is not a serious deficiency unless you use and sharpen a mitsuura chisel a lot, or have a heavy hand when sharpening the ura. The negative impacts are minor in most cases.

 I just want you to be aware of these peculiarities and to be gentle when sharpening mitsuura blades.

C&S’s 24mm Ootsukinomi. Notice the shinogi shape

These are not chisels most people will ever have need of but as long as humans are doing timber framing, there will always be a demand for this unique tool.

C&S’s 24mm Ootsukinomi (face)
C&S’s 24mm Ootsukinomi (side)
C&S’s 24mm Ootsukinomi (Ura)
C&S’s 48mm Ootsukinomi (mitsuura)
C&S’s 48mm Ootsukinomi (side)

YMHOS

© 2019 Stanley Covington All Rights Reserved

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.

The Ancient Art of Hand Forging

Those who hammer their guns into plows, will plow for those who do not. 

Thomas Jefferson

Hand forging is an ancient blacksmithing technique that, from the viewpoint of cutting tool performance, has been almost entirely replaced in modern times, but never surpassed. Understanding a little bit about this technique and its history is helpful in understanding what a good blade should be.

Before motor-powered machinery and gas-fired forges, steel was very expensive. It took a lot of expertise, fuel, manpower and endless hammering over long periods of time to turn rocks into useable pieces of steel, an economical reality that shaped civilization for millenia. International economics aside, all steel was of necessity hand-forged back then.

This is not an efficient process compared to drop forging or press shaping. It consumes more time and fuel, and requires more labor, skill and experience. It is contrary to modern mass-production methodology. It’s a job for a trained blacksmith who demands a fair wage, not a seasonal factory worker in Bümfüq Guangzhou intent on earning enough cash to put a new corrugated sheetmetal roof on his family hovel in the countryside.

In the final analysis, hand-forging is both unprofitable for corporations and too expensive for consumers who actively value low cost and appearance above performance. No wonder it’s as Dead as Disco.

You may recall people talking about how they prefer to use hand-forged antique chisels and planes because they are superior. Those old tools certainly don’t look superior to modern tools, and they aren’t cheap. But are they superior? And if so, why?

The essence of hand forging is using hammer, tongs, anvil and forge (charcoal/gas fired) to violently shape the metal during a series of heating and cooling cycles. The combination of hammer impacts and repeated heat cycles (heating, cooling, reheating) breaks the relatively isolated, large clumps of carbide crystals into uncountable small crystals, distributing them more evenly throughout the steel’s matrix, producing the sharper, more durable, and most desirable “fine-grained” steel.

The properties of this steel are what make it valuable.

A “Tatara” furnace in Japan used to create a “bloom” of “Tamahagane” steel from “satetsu” which translates to “sand iron.” This is the traditional steel that was used throughout Japanese history prior to the importation of Western steel from England in the 1860’s
A clump of Tamahagane (“Jewel Steel”) as it is sold from the bloom furnace. It contains lots of voids and impurities that make this material entirely unusable in modern tool-manufacturing processes.
Related image
A clump of Tamahagane early in the forging process. Most of this material will be lost as waste before a useful piece of steel is born.
After the Blacksmith hammers the raw clumps of Tamahagane hundreds of times, he then forms it into numerous small flat steel patties, which he breaks into the pieces shown in this photo in preparation for forge-welding them into a single larger piece of steel that he can then forge into a blade.

Let’s examine some of these coveted properties. The first is is that it is tougher than steel of lesser quality, meaning it is less likely to fracture due to crystalline defects. In the case of swords or knives it means the blade can cut and chop without breaking when subjected to stresses that would destroy a blade made of lower-quality steel.

The second and third ways fine-grained steel is superior is related to the first. The consistent crystalline structure with its finer carbide crystals distributed more uniformly throughout the matrix results in a cutting edge that can be made sharper, and that will retain that sharpness longer than steel of lesser quality. Of course, realizing this performance depends on the quality of the materials employed, and the skill and diligence of the blacksmith.

Many antique tools were made during a time when steel was expensive, and hand-forging was the only way to shape it. In fact, in the case of critical tools such as swords, this process included forging and reforging clumps of impure iron, folding and refolding the resulting mass into itself hundreds of times to remove impurities and adjust the carbon content, typically resulting in the a loss of 75+% of the original material’s mass. That’s a lot of material and manpower tossed onto the ash pile.

I call these tools critical not just because of their important functions but because of the implied warranty that went with them. For instance, if such a blade failed in battle, the blacksmith’s implied warranty went beyond financial compensation and involved the loss of his body parts at the hands of his vindictive customer’s surviving family members. How’s that for an “extended warranty?”

But any decent steel cutting tool was time consuming and expensive to produce. Until quite recently, blacksmiths did not have tools such as infrared temperature gauges, oxygen sensors, or hardness testers. All they had were their hands and Mark 1 Eyeball, so it took many years of training under a master for a blacksmith to learn how to make a good blade and survive.

Quality control was a big problem back then, but the blacksmiths in Scheffield, Philly, Solingen, Fukuoka and elsewhere still managed to make excellent blades of all varieties with fine-grain steel as the customer demanded. Most of those surviving blades are superior to what is manufactured in the West today. Certainly better than anything made in Chinese factories.

Drop-hammer forging parts in China

Unfortunately, it is impossible to judge a piece of steel’s crystalline structure with the naked eye, a fact mass producers exploit nowadays to make huge profits selling low-quality tools made from scrap at relatively high profits based solely on the tool’s appearance as it hangs on the hardware store wall encased in its impermeable armor of clear plastic. Lower-quality tools became widely acceptable once a generation or two of consumers that knew the value of cutting tools hand-forged from high-carbon steel left for the big lumberyard in the sky to be replaced by more urbanized generations that valued low cost and appearance more than performance.

Sadly, while the quality, consistency, and workability of steel as a material has greatly improved, the ancient technique of hand-forging has been abandoned throughout most of the world, skilled blacksmiths are almost extinct, and blade performance has suffered as a direct result.

Hand forging is still practiced by some blacksmiths in Japan, where the greater quality and performance this technique provides are still highly appreciated by craftsman obsessed with performance. Accordingly, our chisel and plane blades are made from modern high-quality high-purity steel produced by Hitachi metals instead of the much more expensive and difficult to work traditional Tamahagane. However, our blacksmiths hand-forge every single blade in their one-man forges through a minimum of three heats to form a fine-grain steel with the characteristics noted above that Japanese professional woodworkers demand.

鉋の製造工程
A composite photo of Nakano Takeo forging a plane blade.

YMHOS

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.

Sharpening Part 13 – Nitty Gritty

“The true mystery of the world is the visible, not the invisible.” 

Oscar Wilde

In this post we will dig into a few important nitty gritty points about sharpening stones everyone needs to know. Perhaps you already know all these points, but please ready your shovel because there may be at least one buried surprise.

A Flea’s-Eye View

When seen under high-magnification, the surface of a sharpening stone looks like millions of densely-packed stones embedded in a flat field. The smaller the stones, the finer the grit.

As the blade is pushed and pulled over these stones, they scratch and tear metal from the blade’s surface leaving behind scratches corresponding to the size of these small stones. This violence continues until the blade’s ura and bevel form a clean intersection of two planes.

A view of a blade sharpened with 1200 grit diamond plate showing the furrows left by individual pieces of grit

Seen under high-magnification, the cutting edge is jagged where these furrow-like scratches terminate at the cutting edge. To some degree, it may even look like a serrated sawblade. Some blades, like kitchen knives and swords, are used in a slicing motion to cut soft materials like meat and vegetables and enemy arms, and their performance benefits from a serrated cutting edge more than a highly-polished edge, and so do not need to be highly polished on fine-grit sharpening stones. 

Plane and chisel blades, however, are used to cut wood, a material typically harder than foodstuffs, in a straight-on direction, not in a slicing motion, for the most part. In this situation, a rough, serrated cutting edge is weaker than a highly polished edge because the jagged edges are projecting out into space like the teeth of a handsaw blade, and are relatively unsupported and more easily damaged than a highly-polished blade with smaller, more uniform scratches terminating more cleanly at the cutting edge. 

Therefore, in order to produce a sharp durable blade, we must make the microscopic cutting edge smoother and more uniform by using progressively finer grit stones to produce shallower and narrower scratches, and a thin, uniform cutting edge.

But how fine is fine enough? There is a curious phenomenon related to friction that is applicable to cutting edges, and is useful to understand. 

The Friction Paradox

Imagine a cube of heavy stone with its downward flat face resting on the level, flat surface of a larger slab of similar stone. Let’s say it takes some specific measure of force pushing horizontally on the stone cube to overcome the static force of friction between the two stone surfaces in order to make the cube start moving. 

If we gradually increase the degree of polish between the two contact surfaces and measure the force required to start the cube moving at each progressively higher level of polish, we will find the force decreases with each increment of increased polish, for a time. This is at least partially because the irregularities between the two surfaces (asperities) do not interlock as deeply when the surfaces become more polished. 

However, at some point, more polishing brings the surfaces of the two stones into such intimate contact that the molecular attraction between them, and therefore the force necessary to move the cube, actually increases. 

The Inflection Point

The same phenomenon occurs with tool blades. If you sharpen and polish your blades past a particular point, the friction and heat produced between blade and wood will increase, as will the energy that must be expended, while the resulting quality of the cut and durability of the cutting edge will not improve significantly. Of course, the time and money invested in stones spent sharpening past this point will be mostly wasted.

The inflection point where additional polishing yields increased friction with little improvement in cut quality will depend on your tool and the wood you are cutting, but you can gain a pretty good idea of where it is if you pay attention over time. While the sharpening stone manufacturers hate my saying it, in my well-informed opinion there is little practical gain, beyond self-satisfaction, to be had from sharpening chisels or planes past 6,000~8,000 grit, making this range of grit an inflection point in my mind. What about you?

Conclusion

I encourage you to conduct your own experiments to determine the inflection point in the case of your planes and wood you cut. Many who figure this out save themselves significant amounts of time and money sharpening over the long-term.

To those of our Gentle Readers that love sharpening more than woodworking, and enjoy putting money in the pockets of sharpening stone manufacturers more than keeping it for themselves, I apologize for pointing out the floater in the punch bowl. But you probably would have it noticed it eventually anyway, if only from the taste difference.

I will touch more on this important point in the next exciting installment in this scientificish adventure.

YMHOS

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 below.

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

Even monkeys fall from trees (猿も木から落ちる)

Japanese saying
A famous wood carving of 3 monkeys located at Nikko Toshogu Shrine post resconstruction that illustrates a famous saying originating in China that also works as a pun in the Japanese language. From right to left: See no evil; Speak no evil; Hear no evil (見ざる、聞かざる、言わざる).

Ideally, a tool blade will have absolutely uniform dimensions: the right thickness and taper, perfect cross-sections, uniform curvature, and straight edges and surfaces. However, professional grade Japanese tools are not made on CNC machines, but are hand forged, and have dimensional imperfections. Indeed, imperfections are part and parcel of all human endeavors. Most imperfections don’t matter; Sometimes they make the tool better; Other times they need to be remedied.

You, Gentle Reader, may not notice that the blade or cutting edge of one of your chisels or planes is “skewampus,” and consequently the cutting results are less than ideal. You may blame those poor results on your technique in using the tool or the irregular wood grain, when the real problem is the shape of the blade’s cross-section, or your unintentionally sharpening the blade with a skew. We will examine this problem in this post.

We will also look at the curved or “cambered” cutting edge profile in plane blades, the benefits and undesirable results it can produce, and how to incorporate this blade profile intelligently into your woodworking repertoire.

Many people, like monkeys in trees, learn bad habits from their friends and teachers. We hope this post will help you understand what is going on with your woodworking blades, and how to shape and sharpen them intelligently instead of just monkeying around. Please be sure to BYOB (bring your own bananas).

A serious craftsman doing Fine Woodworking in a Pixie-free workshop (notice the strategically-placed boots).

Dealing With Skewampus Blades

Skewampus is an interesting word I learned from my mother. I am told it is a combination of the word “Cattywampus” meaning “in disarray,” and “askew.” I think it is the perfect word for describing the ailments some blades suffer.

While less than ideal, it is not unusual for the thickness of a chisel blade’s cross section to vary slightly across its width, with one side being thicker than the other, forming an irregular quadrilateral cross section. This irregularity is found in plane blades too, but it is not typically a problem. Since there is more steel on the thicker side, the cutting edge will tend to develop a skew during sharpening.

Japanese plane and chisel blades are formed by laminating a layer of hard steel to a much softer body made of extremely low-carbon steel or iron. If the lamination exposed at the cutting edge is not uniform, the area of the blade with more hard steel touching the sharpening stone will abrade slower than areas with less exposed hard steel such that the cutting edge will tend to become skewed during sharpening. Perfection is not required, but the uniformity of the lamination is an important detail to observe when purchasing Japanese tools.

Likewise, Western plane and chisel blades that are not uniformly heat-treated, and that exhibit differential hardening across the bevel’s width, will also tend to become skewed during sharpening as one side of the bevel abrades quicker than the other. This problem is more common than you might imagine, especially in the case of inexpensive tools where appearance and low price are given higher priority than quality.

Anyone that has experience bidding high-dollar construction projects will understand the statement “the most profitable job may be the one you lose.” Cheap tools are much the same way: that low-cost chisel or plane may look good on paper, but if you count your time worth anything, if you dislike headaches, and real-world performance matters to your bottom line, then such a tool is often disastrous. Caveat emptor, baby.

A chisel or plane blade that has an irregular cross section or a skewed cutting edge may not be a problem for many cutting operations. However, when cutting mortises, a chisel blade with a skewed cutting edge or irregular cross section will tend to drift to the side gouging the mortise’s walls and ruining tolerances. If you find that your mortise walls are gouged, or that tolerances are poor, check your chisel blade’s shape, and correct any deformities.

Like all human work spaces, Japan’s smithies are not immune from pixie infestation despite annual blessings by Shinto priests and periodic offerings of rice, salt and wine to the spirits. In a previous post we discussed supernatural predators, so I will refer you to it for antidotes to pernicious pixie pox. But the deformities we are examining in this post are more often the natural result of the human eye misjudging hammer blows or non-judicious use of grinder wheels rather than precocious pixies at play.

If your blade’s deformity is not excessive, you can compensate by applying a little extra pressure on the blade’s thicker side while sharpening it. 

It is interesting how a little off-center pressure on a blade being sharpened over many strokes can change its shape. Many people unintentionally deform their cutting edges by not paying attention to the amount and location of the pressure their fingers apply. A word to the wise.

Another potential solution is to skew the blade in relation to the direction of travel when sharpening the bevel. This works because the leading corner of a skewed blade is abraded quicker than the trailing corner. But once again, inattention causes many people to skew their blades when moving them around on their sharpening stones unintentionally creating, instead of intentionally correcting, skewed cutting edges. There is nothing wrong with skewing the blade when sharpening so long as you are aware of the distortion this practice can produce and compensate accordingly. Another word to the wise.

If these methods don’t compensate adequately, you may want to grind and lap a chisel blade to a more uniform cross-sectional shape. A chemical bluing solution used afterwards will help conceal the shiny metal exposed by this operation if your chisel objects to the shiny spots. Some of them can be quite vain, you know.

A chisel with a an adequately uniform lamination and cross-section, and nice polish.

Cutting Edge Profiles

Many people have access to electrical jointers and planers, but relatively few have industrial equipment with the capacity to dimension wide boards such as tabletops. And of course architectural beams and columns are typically too long or too heavy to dimension with most stationary electrical equipment.

The choices available to most people for dimensioning such materials therefore are either handheld electrical power planers and/or sanders, or axes, adzes and hand planes. Powerplaners, sanders, axes and adzes are beyond the scope of this article, but we will look at hand planes.

I need more than one plane? You can’t be serious!

Although the very idea gives some woodworkers vapors (I don’t mean gas), an efficient craftsman will have multiple planes with cutting edges honed to profiles matched to specific operations.

Everyone that dimensions larger pieces of lumber by hand needs a plane with a wide mouth and a curved or “cambered,” cutting edge called a “scrub plane” in the West, and “arashiko kanna” in Japan.

This variety of plane excels at hogging a lot of wood quickly when the craftsman needs to significantly reduce the thickness of his lumber.  If the blade is narrow and curvature is deep, this plane will hog wood quickly, but leave a deeply rippled surface, often with bad tearout.

One might also have a second arashiko, or jack plane with a wider blade with a shallower curvature for the next steps in the dimensioning process. Such a plane will not hog wood as quickly, but it will produce a surface that is closer to flat and smooth and with less tearout. You can see the advantage of having two arashiko planes, or a scrub plane and a jack plane, with different cutting edge profiles when dimensioning lumber.

Many Gentle Readers use electrical-powered planes to dimension lumber before turning it into furniture, doors, chairs, or sawdust, etc. and are aware that planers always leave tiny ripple-like scallop cuts on the wood’s surface, along with some tearout. This will not do as a final surface. A hand-plane finish is far superior, but it doesn’t make sense to remove any more than the bare minimum of wood necessary to remove the washboard.

A finish plane is the perfect tool for this job on condition that it is sharp, set to a fine cut, the chipbreaker is tuned and set properly, the blade profile is appropriate for the width of the wood to be finished, and the wood does not have too many large knots. In one or two passes such a plane can easily remove the ripples and leave the wood clean and shiny without changing its dimensions much at all.

Assuming the wood is cooperative and one knows how to sharpen and setup their plane properly, blade profile frequently remains a key factor many fail to grasp. Obviously, the curved cutting edge of a scrub plane cannot produce the perfectly flat surfaces required for joining two pieces of wood together. On the other hand, the corners of a perfectly straight blade will leave clearly visible steps or unsightly tracks on the surface of a board wider than the blade, which is not a problem when rough dimensioning a board, but is painful to see if the board’s surface is to be left with just a planed finish.

So how do we solve this conundrum? When finish planing, the professional approach is to use two planes each with a different cutting edge profile. The first type of finish plane has a perfectly straight cutting edge used to plane pieces narrower than the blade’s width. Since the blade’s corners are not riding on the wood while cutting it, they won’t leave tracks and ridges.

The second type of finish plane found in the professional’s toolkit has a curved cutting edge, or more correctly, curved just at the corners to prevent it from leaving tracks and ridges when planing boards wider than the blade. Nearly all the edge is left straight, but creating this tiny amount of curvature at the right and left corners causes it to smoothly disappear into the plane’s mouth so no tracks are made and any ridges are nearly impossible to see or feel. In other words, the corners of the cutting edge never touch the surface of the board, and so don’t leave discernible tracks or ridges. The finer the cut made the smaller any ridges created will be. Indeed, where a high-quality surface is required, the final cut with the finish plane will produce shavings thin enough to see one’s fingerprints through.

You may want to reread the previous two paragraphs to make sure you understand what these two cutting edge profiles are and what they can accomplish before you read further.

Naturally, a professional doing high-quality work needs at least two finish planes, one with a straight cutting edge used to produce flat, precisely-dimensioned surfaces on wood narrower than the blade’s width, and another finish plane with a cutting edge very slightly curved at the corners used to finish wider surfaces.

There are those that advocate using a curved blade, sometimes dramatically “cambered” as some call them, for all applications. Those who teach this sloppy technique twist themselves into knots justifying tricks to approximate flat surfaces using such blades. I have no doubt this is an ancient technique, but I think it is a sad practice that sprung from the carelessness of some craftsmen in flattening their sharpening stones, and with time this bad habit became a tradition in some quarters. I strongly suspect fans of this strange way of doing business habitually sand all visible surfaces anyway so tracks and ridges are not a problem for them. But the fact remains that perfectly flat, track/ridge-free surfaces work best for joinery.

Tradition and “monkey see monkey do” are a useful place to start, but as his skill level increases, the thoughtful and efficient craftsman will eventually seek to confirm the validity of the traditions he has been taught. I urge you to get started early.

Sadly, too many people never notice the strange instruction label pasted to their boot’s sole, nor that smelly stuff sloshing around inside.(ツ)

monkey-see-monkey-do
Mommy monkey teaching baby monkey bad habits. When will they ever learn?

Conclusion

As we come to the end of this post, my advice to you, Gentle Reader, is to learn two bedrock basic skills to perfection. First, learn how to keep your sharpening stones flat; And second, learn how to sharpen your blades to have a straight cutting edge. Everything else will flow naturally from these skills. Your blades deserve it. We will talk more about these subjects in the future.

In this post, we have discussed 12 serious points about plane and chisel blades and how to use and improve them all but a few woodworkers in the West are unaware of, or ignore, but which are common knowledge among professional Japanese woodworkers in advanced trades. While condensed, it is enough information to fill a book, but we are giving it to you for the price of bananas (BYOB, remember?). We hope you picked up on each point, and test those that are new to you.

The next installment in this simian soap opera of sharpening will focus less on monkeyshines, and more on stones and techniques. Please stay tuned.

YMHOS

I can’t wait to read the next post!!

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.

The Upside-down Hanging Woman

Warning: This is a special Halloween post, but it may not be suitable for children.

「竹久夢二 美人画展 ―わたし美人?―」竹久夢二美術館で、美人画の変遷を辿る作品・資料約200点 - 写真2
Osei, the luckless heroine

The Japanese love scary stories of all kinds, especially those that have a sticky ending. In keeping with the Halloween season, I want to share this story about an unfortunate woman on the way back home. The ending isn’t what could be called sticky, just the opposite in fact, but it still includes lonely places and good food, helpless women and ropes, indeed everything a scary Japanese folk tale needs. Enjoy.

Long ago and far away there was a woman named Osei. She was 25 years old.

She had traveled from her home to visit her parents in a different village for several days. It was a half-day journey for a woman, normally one her husband or younger brother would have accompanied her on, but they were both too busy to travel with her this time.

Anyway, let’s walk along with Osei on her lonely path through a dim bamboo thicket at twilight.

Suddenly a man appeared by the side of the path, as if he had been waiting for her. Osei screamed in surprise.

The path through the bamboo forest
matome263
The bad guy

The man was huge and looked just like you would imagine a bandit would be with a long, unkempt beard and wearing a dirty sleeveless kimono. He grabbed Osei’s slender arm violently and dragged her in among the thick bamboo stalks. Osei screamed like a banshee on fire but the thick silent forest swallowed the sound without an echo. Only a fox and the mice he was hunting nearby heard Osei’s calls for help.

Osei struggled frantically to free herself from his iron grip, but without stopping the man just looked back at her admonishingly and said “Calm down, I’m not going to eat you! I just want you to be my wife.”

The large, dirty man held tightly to one of Osei’s arms, while Osei’s feet and free hand scrambled in the fallen leaves on the forest floor trying to get back to the path. Hearing his words, she managed to gasp out “Wait, wait! I can’t be your wife, I already have a husband and two small children waiting for me at home! Please let me go!”

Without releasing her the man stopped and with a puzzled expression said “Think about it. There is only endless drudgery waiting for you at your husband’s drafty hovel. And the best you will have to eat is rough barley rice and pickled greens, right?” “But if you come with me your life will be easy. You can relax indoors all day and eat delicious foods. That’s a lot better than your life now, I wager.” He made other strange arguments about nice clothes and servants, but Osei didn’t hear a single word, she just continued to scream and struggle.

Giving up on trying to convince Osei with words, the man tied her up, threw her over his shoulder, and strode purposefully away into the bamboo forest. After a while, the forest opened up to a clearing with a single house. The house was large and well made, like a Governor’s mansion.

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The mansion in the woods

The man carried her into the house and lowered her onto the floor. Looking steadily into her eyes he firmly said “You are now the woman of this house. Your life here will be easy, so long as you don’t go outside. You will have delicious things to eat and a new silk kimono to wear everyday. Then you will understand that what I have said is true. Even if you think I am lying, stay here for just one month anyway, and after that you will be free to go. So stop all this hysterical wailing.”

Osei continued to cry, but after a while dinner appeared. It was everything the scruffy bandit said it would be.

Just a light snack

Osei grew up on a farm and was a poor farmer’s wife so she had never even seen such luxurious food before. But thoughts of her husband and children made it impossible to eat a morsel, so she just sat in a corner of the room and cried in despair.

But humans are calculating creatures unable to live on affection alone. After three days she became so hungry she finally relented and ate a mouthful of food.

There were foods from both the sea and the mountains, wonderful dishes she had never seen before much less tasted. She didn’t forget her husband or children for even a second, but rationalized that the separation would only be for a month. As the days passed she began to eat regularly a little at a time.

Four meals a day, nice clothes, servants to cook and clean, and no work. What more could a woman possibly want?
Osei enjoying a picture book between meals

Osei spent each day alone in her room simply eating and reading picture books the man brought to her, so she was not especially bored.

Most importantly, the man did not pressure her for physical relations, so the tension between them gradually relaxed.

Eventually, however, Osei had read every picture book several times and was left with nothing to do. She was bored.

One day as the smelly bandit was taking his usual afternoon nap she snuck out of the house as quiet as a mouse wearing fuzzy pink slippers. She slipped from the veranda into a large garden with a big white kura warehouse off to the side. She heard voices from inside the warehouse, and what sounded like rain dripping from a leaky roof. Osei was curious and peeked into the warehouse’s open doors. What she saw inside shocked her so badly she had to kneel to keep from falling over. 

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Japanese “Kura” (蔵) or “Dozo” (土蔵) are a type of warehouse building with a wooden structure and thick walls and ceiling of adobe plaster. The mass of the adobe moderates interior temperature changes helping to preserve foodstuffs and goods. More importantly, a well-built Kura will withstand a serious fire protecting the people and valuables inside, a tremendous benefit in light of the terrible fires that have historically and frequently ravaged Japan’s cities. Owning a Kura was not only a sign of wealth but was important to creating and protecting wealth.
Image result for 土蔵
Dozo, being made of adobe, essentially clayey mud and straw, are vulnerable to damage from water and impacts. Two methods of protection traditionally employed were a fired-clay tile roof, interim eaves also with roof tiles, and a tall wainscot of fired-clay tiles, or even stone tiles as in this photo.
Notice how thick the adobe walls are, and how all flammable building materials are protected behind adobe and plaster. The thick shutters too are filled and wrapped with adobe and a white plaster coat and have stepped edges that interlock to seal out smoke, fire, insects, rodents and thieves.
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The entry doors are also adobe and plaster over a wooden frame, often with metal panels to add further stiffness and security. The outer fireproof doors are left open during the day while the lighter and more easily-operated inner wooden doors are kept closed to keep out insects, rodents, and pilfering hands. At night, or during a fire, the heavy insulated doors are closed and locked. A well-made Kura will not only protect a family’s or business’s wealth, but is the perfect emergency refuge during fire or flood.

What Osei saw in the kura was dozens of bound women hanging upside down from the ceiling beams by ropes around their ankles as naked as the day they were born. Every single one of them was plump and sweating a yellowish liquid from their hair follicles and face which fell into a clay pot placed on the floor below each woman making a “drip, drip, drip” sound.

Osei was deeply ashamed at her indolence while these women had been suffering so close by. She began to cry at the sight. One of the women noticed Osei and whispered “Run! Hurry run away! If you don’t escape you too will end up hanging here with us while he steals your body’s oil!” With that all the hanging women looked at Osei pitifully and said as one “Run and bring us help!”

Osei was so shocked at first she couldn’t respond to the women’s pleas, but after a few minutes she did manage to stand and run away like a scared rabbit as fast as she could. As she fled through the forest and thickets daylight failed and she became even more fearful, but she continued running until at last she saw a light in the distance. It was an old farmhouse. She ran to the door and banged on it loudly until an old snaggle-toothed white-haired woman slid open the door.

A traditional country farmhouse with a straw-thatched roof and smoke hole above the kitchen located towards the building’s right side. Notice that the right third of the building, including what would serve as the kitchen, is not raised. This area has an earthen floor and serves as workshop, storage shed, or even animal shed, depending on the farm’s needs. No glass windows, of course, just paper shoji doors and sliding wooden shutter doors at the perimeter.

“What’s the matter; why are you so panicked?” the old woman asked Osei. Reassured by the old woman’s concern Osei quickly explained what had happened. 

“Well, come inside dear. I had no idea such a scary ruffian was skulking around these mountains,” said the old woman. “Oh no, I hear someone coming!” she suddenly barked, and pulled Osei inside sliding the door closed with a loud “clack!” Osei peeked through a crack at the doorframe and indeed saw a large figure running through the dark bamboo forest towards the house. “That’s him! That’s the man! He’s coming!” she gibbered in a low panicked voice.

The old woman guided Osei to a ladder going up to the house’s attic. “Quickly now, climb this ladder and hide above. There is a pile of hemp bags in the corner. Climb inside one of them and stay very very quiet until I get rid of that animal. I will hide the ladder so he won’t find you.”

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The roof structure of the farmhouse.
The corner of the farmhouse attic where Osei hid.

Osei climbed the ladder, found the pile of bags, and curled up inside one as small and quietly as a potato bug. She could hear someone banging on the door below, and the old woman saying “I’m coming, I’m coming! Wait a second!” As the door slid open she heard the large man’s voice saying “A woman just came here, didn’t she!”

The old woman responded “No one but you has come here today.” The man’s voice said “Don’t lie, I saw her!” 

“How could you see anything in this darkness?” said the old woman.

“You have an oil lamp burning inside. I saw her shadow at this very door when you opened it just now!”

“You must have seen my shadow twice,“ the old woman argued.

The man was angry now and spit out “I’m no fool! No way I would mistake an old hag like you for a young woman even in the dark.” “You’re trying to steal the woman I was preparing!”

The old woman lowered her voice, but Osei could still hear her response “Haven’t you got enough women already? Couldn’t you share just one with your old mother?”

The man continued to argue with the old woman, but eventually he calmed down and spit out “ Just this once, then, mother.” “Where have you hidden her?”

“In the attic,” responded the snaggle-toothed old woman pointing upwards with a finger and grinning. “Inside one of the bags. And while your at it, would you be a good boy and hang a new rope for me?”

“You know, you’re a lot of trouble for such an ugly old hag!” responded the man’s voice.

Hearing this Osei tried to escape from the bag, but before she could get away she was wrapped in rope like a butterfly caught in a spider’s web. The bag was suddenly and powerfully torn open and she was pulled out, only to be tied with a thick, rough rope around her ankles and suspended through a hole cut in the ceiling above the hallway below. Clearly, the rope and hole had been prepared well in advance and used before.

Osei looked around and saw the ruffian and his mother looking back at her. Of course, they appeared to be upside down. Looking at the floor below, Osei noticed a large clay pot placed directly below her with what appeared to be some yellow oil in the bottom.

Before long, a slow drip, drip, drip, … of oily sweat fell from Osei into the pot.

A sad ending to an all too common story of suffering.

The End

(A folktale from the island of  Kikaijima, located between Kyushu and Okinawa)

月下竹林骸骨行之図
Happy Halloween from your friends at C&S Tools!

YMHOS

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The Varieties of Japanese Chisels Part 14 – The Kote Nomi (鏝鑿Trowel Chisel)

You cannot mandate productivity, you must provide the tools to let people become their best.

Steve Jobs

This post will be a little different from my normal post for several reasons. First, because although I love this tool, I can’t procure them anymore, so it is more of a show and tell. And second, because I have a couple of stories to tell about the blacksmith that made it, and the store that sold it to me.

The Kotenomi

The kote nomi is written 鏝鑿 in Chinese characters meaning ” trowel chisel.” It is not an elegant name, but is accurately descriptive. It is essentially the same as the Western ” cranked-neck chisel. ” It is used to pare grooves, dadoes, sliding dovetails, rabbits and mortises, anywhere the handle of a regular paring chisel would get in the way.

The sides have a steeper bevel than regular chisels, much like a shinogi usunomi, to help it get into tight places and cut right up against the sides of sliding dovetail groves, dadoes, etc..

These are not easy chisels to sharpen because of both the offset, and the tendency for the neck to get in the way.

This is one of those chisels that you may not need often, but when you do need it, you need it badly.

Kiyotada kotenomi
Kiyotada kotenomi

The shape of the Kiyotada kotenomi in the 3 photographs above is graceful, elegant and minimalist. The filework is very nice. The black oxide skin is consistent, indicative of a perfect heat treat. The blade, made of Shirogami No.1 steel (aka “White Steel 1”) is, unsurpassed by anything I have experienced. It is one of those rare tools that clears the mind as it cuts wood.

Background

The kotenomi in the pictures above have an interesting back story. It was forged by a famous and exceptionally skillful blacksmith named Kosaburo Shimamura (島村幸三郎)using the brand ”Kiyotada” (清忠). It is not the standard Japanese kotenomi in terms of design, appearance or performance, but is based on those forged by an even more famous blacksmith named Hiroshi Kato (加藤廣1874-1957) under the name of Chiyozuru Korehide (千代鶴貞秀), one of Japan’s greatest tool designers and blacksmiths. Much of his work is seen as great works of art in Japan.

As Mr. Ichiro Tsuchida told the story to me, he lent one or more of his collection of Chiyozuru Korehide kotenomi to Mr. Shimamura and asked him to forge some just like it to sell in his tool store Sangenjaya in Tokyo. After much trial and error, Mr Shimamura succeeded in approximating the Chiyozuru design in the chisels shown here.

As you can see from the pictures, the blade’s sides are sloped inwards from ura to face, a detail that provides clearance when cutting sliding dovetails, a joint this tool excels at making.

I use it, as well as my other Kiyotada kotenomi, for making dadoes, rabbets, and inletting swamped rifle barrels in reproduction flintlock barrels (sadly, I can’t pursue that activity here in Japan).

As you can see from the photo below, standard kotenomi are very clunky in appearance and crudely finished compared to Shimamura’s chisel, with a more abrupt, angular transition between neck and blade, whereas the handle in the Kiyotada design approaches the neck at more of an angle, a detail that stiffens the neck, reduces the bending moment on the neck/blade junction, and helps force flow into the blade more smoothly.

The standard model works just fine, but a comparison of their the appearance and tactile qualities would be like a Lear jet and Cessna 172: both vehicles will get you there, but the speed, comfort and style will vary.

Standard kotenomi chisel (face view)
Standard kotenomi chisel (shoulder view)

The Kiyotada Brandname

A bit if trivia some may find interesting. The Kiyotada brandname was registered by, and remains the property of, a tool store in Tokyo called ” Suiheiya” (水平屋).

Suiheiya means ”level store,” probably named for the bubble-level tool imported from the West and which is so critical to construction and other trades. This store is old and was once the largest tool retailer in Japan. Last time I visited it was still large and packed to the concrete rafters with planes and chisels.

I first visited Suiheiya when I was a student in Tokyo in the ‘80’s when the premises was a 2-story wooden structure probably built right after the end of WWII. The proprietor was an old sourpuss who had no patience with foreigners and treated me like a shoplifter-in-training with a turd perched on my head. For some reason I can’t put my finger on I didn’t visit the store frequently, but I did buy this and other tools from him.

But I digress. Shimamura San made chisels and knives for Suiheiya his entire career and marked those tools with Suiheiya’s own Kiyotada brand. I suppose it would have seemed silly, or at least confusing, to mark a chisel or knife with a brand that could only be read as ”bubble level.”

I’m unsure how it happened, but as his products became more famous Shimamura-san made chisels for other retailers using the same Kiyotada brand. I was told by the owner of Suiheiya that Shimamura-san used the Kiyotada brand for all his products with Suiheiya’s permission.

By the way, although Shimamura-san has gone to the big lumber yard in the sky, Suiheiya continues to sell planes and chisels with the Kiyotada brand, although they are not made by Shimamura-san, who is busy with more important matters nowadays.

Sadly, my blacksmiths won’t make kotenomi for me anymore. I tend to be picky about quality, and with Kiyotada’s kotenomi as the standard, you can see why customer satisfaction in my case is difficult.

YMHOS

© 2019 Stanley Covington All Rights Reserved

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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.

Image result for brass bench dog
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

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

© 2019 Stanley Covington

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.