All times are good for those who know how to work and have the tools to do so.
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.
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.”
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.
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.
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.
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.
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.
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.
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.
You cannot mandate productivity, you must provide the tools to let people become their best.
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 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.
The shape of the two Kiyotada kotenomi shown in the 10 photographs on this page 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.
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).
The following are pictures of the standard garden-variety kotenomi.
As you can see, the 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.
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.
The Oiirenomi (pr0nounced Oh-ee-reh-no-me) is the most common variety of Japanese woodworking chisel, and the style best known both inside and outside Japan. There are several types of oiirenomi. In this post we will look at the most popular type of oirenomi called the ”mentori oirenomi” ( 面取り追入鑿) meaning ” beveled” oirenomi.
As mentioned in my previous post in this series, nomi means ” chisel, ” but the term ”oiire” 追入れ” is not so straightforward. It is composed of two Chinese characters: ”Oi” 追いmeaning ”to chase” or ” to follow,” and ”ire” 入れ meaning ” insert” or ”place in.” I am uncertain of the origin of this word, but some hints of the original meaning may perhaps be deduced from the characters.
As the name suggests, this chisel’s face is beveled at both sides making it lighter and better able to get into tight locations than the older-style kakuuchi oiirenomi, the forerunner of this chisel, which we will examine in a future post.
I think most people agree that the two bevels moving up the blade, curving around the shoulder, and feathering into the neck give this chisel a sculptural, elegant appearance. The bevels do sacrifice some stiffness and authority compared to the kakuuchi style, but clearly, these compromises are acceptable to most consumers.
A member of the tatakinomi family, it is designed to be struck with a steel hammer and has a hoop (called a “katsura” in Japanese which means “crown”) on the handle’s end to prevent splitting.
There are larger types of tatakinomi called atsunomi better suited than the oiirenomi to heavy cutting and wasting wood in applications such as timber frame joints, and most of those share the same mentori bevel detail, but oiirenomi are better suited to lighter tasks such as furniture work and interior installation work the same as Western bench or butt chisels.
Oiirenomi in general and mentori oiirenomi especially are light-weight, relatively inexpensive, and handy to use. All woodworkers in Japan own at least a few of these.
Materials and Manufacturing Techniques
Our oiirenomi are hand-forged by traditional self-employed blacksmiths with at least 40 years of experience working in their self-owned one-man smithies. They are stubborn gentlemen absolutely dedicated to quality.
These blacksmiths use only Hitachi’s Metal’s Yasuki Shirogami No.1 Steel (aka “White Steel”) for the cutting edge, a plain, exceptionally high-purity, high-quality, high-carbon steel that does not contain significant amounts of chrome, molybdenum, nickel, vanadium, or tungsten, chemicals which are added to nearly all commercial tool steels to make products easier to mass-produce by factory workers, instead of more expensive skilled blacksmiths, with fewer rejects. These alloys add considerably to the cost of the materials, while resulting in a finished product that will not become as sharp as Shirogami steel, will not hold a sharp edge as long, and will be more unpleasant and more time-consuming to sharpen. If you have the sharpening skills, then Shirogami No.1 is a steel you should experience.
Our blacksmiths perform a minimum of 3 heats to each blade while using hammers and spring hammers to forge this special steel. This “hand-forging” process, combined with the special heat-treatment techniques they have perfected over many years, produces a “fine-grained” steel of the sort that has been coveted by professionals for tools and weapons since ancient times. The final hardness is between 65~66 on the Rockwell C hardness scale. Most Western Chisels are softer at 55~60 HRc. This extra hardness makes the blade stay relatively sharper longer, and the fine-grain crystalline structure of the steel ensures each blade will become sharper without sacrificing durability.
These are professional-grade tools made by craftsmen, not factories, and are intended to meet the severe performance expectations for Japan’s most uncompromising woodworkers, unlike the mediocre-quality but attractive-looking “consumer-grade” chisels peddled inside Japan to the amateur market, and outside Japan to the uninformed. How much bacon do you like with your sizzle?
Our oiirenomi are available individually, or in discounted 10 piece sets (3, 6, 9, 12, 15, 18, 24, 30, 36, 42mm) with Japanese Red Oak or White Oak handles. We have all varieties in-stock ready to deliver.
“Electrical tools are consumables; our tools are part of our bodies. Do not treat tools as just things. It is a mistake to think of tools as just your own. The shape of every tool was not decided recently. Over a long, long time it was decided that this form would be most useful.”
Nishioka Tsunekazu, Temple Carpenter in charge of the Horyuji and Yakshushiji Temple Restorations
There are many varieties of Japanese chisels, and most people, including Japanese, are confused by the meanings of their names, and their various applications. I am not an historian or archaeologist, but I have been using them for over 40 years both professionally and for the fun of it and like to flatter myself I know a bit about them. Perhaps this and future posts will help de-muddle a little of the confusion.
In this first post in the series I will explain the components of Japanese woodworking chisels, and the two main categories. In later posts I will explain the various types of chisels included in these categories in some detail. But let’s begin with some language matters.
Terminology and Translation
Where a suitable English word is available, I will use them, but for the most part, I will employ the Japanese terms converted from Kanji (Chinese pictogram characters) and Hiragana (phonetic Japanese characters) to the Roman letters used in most English-speaking nations.
The word for “chisel” in Japanese is “nomi” (鑿). The Chinese character used to write this word is complicated, so it is normally converted to the phonetic hiragana letters as “のみ.” You will notice that nomi is part of every chisel’s name, so I will use it too.
Structure and Components of Japanese Chisels
The design of Japanese chisels is a little more complicated than their Western counterparts, but the basic components are generally the same. So let us examine the similarities and differences.
Blade and Neck Construction
Traditional Japanese chisels have laminated blades with a body, neck and tang made of iron or very low-carbon steel that remains relatively soft during heat treatment. A layer of high-carbon steel is laminated to this iron body at the blade to form the cutting edge. During the quenching process, this layer becomes very hard, typically 62~67 Rc versus the typical hardness of 58~60 Rc found in Western chisels. The two layers are most visible at the bevel. This additional hardness has both advantages and disadvantages, depending on the crystalline structure of the steel after heat-treating and the skill with which the tool is used and maintained.
In the case of hand-forged (teuchi 手打) blades, this lamination is made by forge- welding the two types of metal over several heats using hammer, tongs, and anvil.
European chisels were also fabricated using this technique before the advent of mass-produced inexpensive steel. Unfortunately, this once-universal excellent technique has been all but forgotten outside of Japan.
Materials & Process
The best professional-grade chisels are made of high-quality iron and the purest plain high-carbon steel. These ancient metals are difficult to work, being very sensitive to temperature and thermal shock and tending to warp and crack badly in less than experienced hands. Many alloys and processes have been developed over the last 60 years to make tool production more profitable using unskilled labor, but for simple cutting ability and ease of sharpening, nothing rivals this combination.
The blacksmithing process involves forge-welding the two types of metal to form a laminated blade, then shaping and hand-forging over multiple heats, followed by carbon soaking and annealing, a coating of secret mud sauce after which the blade is heated to just the right temparature and subject to multiple quenches followed by multiple temperings. The process varies from blacksmith to blacksmith with each craftsman using different formulas and procedures. Of course, warpage must be compensated for by shaping a curve in the blade that straightens out during heat treatment. Learning these skills takes years of hands-on training from a young age under the eye of a master, and decades of dedication to quality. It certainly cannot be accomplished in a mass-production situation, much less by Chinese peasants or even CNC robots.
Mass-produced consumer-grade Japanese chisel are made of pre-laminated strip steel manufactured in steel mills by either cold-rolling or hot-rolling a layer of high-carbon steel to a layer of mild-steel. This material, called ” rikizai” (利器材）or ” fukugozai” (複合材）was originally developed for mass-producing inexpensive kitchen knives as a labour-saving material to reduce manufacturing costs.
Blades made from rikizai typically perform adequately for most consumers, but many professionals seek the higher performance of so-called ” fine-grain” steel’s smaller and more uniformly-distributed carbides found in hand-forged, expertly heat-treated blades. Those who develop the skills necessary to discern the difference between such professional-grade and consumer-grade blades, can never be satisfied with the inferior tool.
Japanese chisel blades have a hollow-ground back (the so-called ” flat” on Western chisels) which makes the harder steel easier to sharpen and keep flat. Without this hollow-ground ura feature you would find sharpening a chisel blade of similar hardness time consuming and almost impossible to keep flat over many sharpenings.
Tang and Ferrule
Japanese chisels appears at first glance to be socket chisels, but they are definitely tang chisels. The handle incorporates a steel ferrule shaped like a truncated cone and called the “ kuchigane” (口金) which translates to “mouth metal.”
This component receives the reaction forces of hammer impacts from the blade’s shoulders converting these thrust forces acting in the handle’s long axis to compression forces acting on the handle’s end thereby preventing splitting and locking the tang tightly into the handle. It is a subtle but clever and effective design that combines the best features of both tang chisels and socket chisels without any of the downsides.
Chisels intended to be struck with a steel hammer have a sturdy steel hoop called a ” katsura” installed at the handle’s end to prevent the wood from splitting. The characters used for this word include 冠, pronounced “kan” or “ kanmuri” meaning “crown” or 桂 meaning Judas Tree or “ knight” （桂馬）as in the chess piece. The word Katsura can also mean “ wig” a term that does not quite work in this case because chisel handles are as bald as I am.
I have the bad habit of anthropomorphising my tools. They hate that, so to avoid giving further offence (they sometimes bite, donchano), I prefer to translate katsura as the more elegant word “crown” instead of the more constrictive word “hoop” or follically-challenged word “wig.”
Just in case you aren’t entirely confused, please note that this same steel hoop is also called a ”sagariwa” (下り輪) which translates to ”drop hoop, ” a term that is accurately descriptive because, over many years of hammer blows, the handle gradually shortens and the hoop “drops,” shifting its position down the handle.
The crown is made of relatively soft but still strong mild steel. In use, it may occasionally be struck by a steel hammer. This choice of material is not based on economics or convenience but on the practical reality that the face of a steel hammer impacting the edge of a hardened steel hoop would get dinged and even deform after enough hits.
But this creates another problem, namely that the crown may eventually become deformed by hammer strikes unless preventative measures are taken. This is not a trivial cosmetic matter because the hoop’s edge may deform to the point it curls back inside itself. Then, if the user continues to beat on the chisel, the hoop will gouge and eventually split the handle.
The best way to avoid this grief is to use a hammer with a flat instead of convex face and to properly setup the chisel when new. For instructions on doing this, please see my earlier post about Setting-up Japanese Chisels.
Another downside to the crown and steel hammer arrangement is that the end of Japanese tatakinoni are far from smooth and can be uncomfortable to use when paring. The solution to this is three-fold. First, setup the crown properly and chamfer and smooth its edges. Second, avoid hitting the crown with hammer so it doesn’t become rough and gnarly. And finally, use a tsukinomi chisel for paring. Life is good.
Chisel handles can be made of a variety of woods, but strong hardwoods such as oak are commonly fitted to chisels designed to be motivated with hammers.
Chisels not intended to be struck with a hammer can be fitted with more brittle but decorative wooden handles such as ebony or rosewood.
The Two Categories: Tatakinomi and Tsukinomi
There are two primary categories of Japanese chisels. I think these same categories apply to other traditions, but in the difference is especially clear-cut in Japan.
The first category is the “tsukinomi “ (突き鑿). Tsuki means “to push,” so tsukinomi refers to push, or paring, chisels. Standard widths range from 1.5mm to 48mm. Handle lengths and materials vary with the type of tsukinomi, the intended purpose, and personal preferences.
Tsukinomi are pushed by hand and sometimes by shoulder in the case of the large ootsukinomi, known in the West as “slicks.” Most tsukinomi have relatively longer, more slender and elegant necks. They incorporate the same kuchigane ferrule at the blade end of the handle, but do not have a steel crown hoop reinforcing the opposite end.
By definition these chisels are not intended to ever be struck with a hammer. Even if the handle does not split, their more slender necks will not endure impact forces gracefully. More often than not they are used to clean and pare to final tolerances joints cut using other chisels.
The second main category of Japanese chisel is called the “tatakinomi” (叩き鑿）meaning “striking chisel.” This is the style of Japanese chisel best known outside Japan. These chisels are stronger and tougher than tsukinomi and are intended to be struck with a steel hammer.
Wooden mallets are not typically used with Japanese chisels. The logic for this practice is simple: A steel hammer is the smallest, lightest, and most energy-efficient way to motivate a chisel. The physics of this are self-evident. Accordingly, the logic behind the tatakinomi design is that, since it must efficiently remove lots of wood, and a steel hammer is the most efficient way to motivate a chisel, the tatakinomi’s handle must be designed and made strong enough to endure being struck by a steel hammer from sunrise to sunset. A simple calculus.
By contrast, the Western tradition of using chisels with inherently fragile handles requiring users to obsessively baby them with relatively soft, energy-wasting, un-aerodynamic, big-ass mallets is illogical and inefficient. But to each his own.
Some people stubbornly insist on using mallets even to strike their Japanese tatakinomi. This reminds me of the country bumpkin that bought a newfangled chainsaw from a hardware store in town to cut firewood only to bring it back the next day complaining it was slower and more work than his old axe and handsaw. The puzzled hardware store owner checked the fuel and spark plug, but found no obvious problems. With a perplexed look he yanked the starter rope. The chainsaw’s motor started right up with a roar and a cloud of smoke. The shocked customer almost jumped out of his overalls in wide-eyed surprise, screeching “ what the hell’s that racket!?!”