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 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.
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.
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.
“Life is not a matter of holding good cards, but of playing a poor hand well.” – Robert Louis Stevenson
So, you finished building that fine cabinet, or 8-panel entry door, or carved balustrade and the day has come to install it at the jobsite. Will you need to cut a bit of gypboard or lath-and-plaster while installing it? Might your chisel get jammed against or into bricks or concrete in the process? Will you need to cut a notch in sandpaper-grit filled plywood or OSB? Any hidden screws or nails in the way that might require more than stern words?
Jobsite installations and remodeling often demand nasty work everyday tools can’t accomplish without serious damage. At that moment, having a tool tougher than the job is the difference between working and whining. This is that tool.
HSS oiirenomi are a modern variation of mentori oiirenomi made using high-alloy steels tougher and more resistant to abrasion and high temperatures than more traditional steels.
These chisels are useful for doing remodeling work and cabinet and equipment installations where plywood, MDF, OSB, LVL, drywall, acoustic board, insulated board, plaster, mortar, underlayment and studs full of hidden nails, and even ALC (autoclaved lightweight concrete) panels need to be cut, trimmed, fitted or demolished. Demolition…Oh joy (not).
Although High Speed Steel (HSS) won’t become as sharp as plain high-carbon steel, and takes more time to sharpen using a grinder and diamond plates, when you need to cut or trim the hard abrasive materials listed above, these blades will keep clippin’ without chippin’ when a standard chisel would be turned into an expensive gasket scraper. Also, one can quickly repair the damaged edge on an HSS chisel with a bench grinder or angle head grinder of the sort found on any construction jobsite without burning or softening the steel, a handy feature indeed.
HSS oiirenomi are hardened using special processes that leave the metal bright instead of creating the black oxide skin typical of standard high-carbon steel blades, an appearance some people find attractive.
Before I tried my first HSS oiirenomi, I kept a couple of old plastic-handled steel-cap Stanley chisels in my toolkit as “beaters” for cutting gritty, abrasive materials. They were soft and instantly dulled, but their edges would dent instead of chipping and were easily repaired. Poor things; some days they ended up looking more like rounded-over wide-blade screwdrivers than wood chisels. HSS chisels are just the ticket for this kind of brutal work.
The chisel pictured above was manufactured by Mr. Usui Yoshio under his brand “Sukemaru” (助丸). He is the fourth generation in this long line of famous blacksmiths.
The blade is one-piece of high-speed steel, not laminated high-carbon steel. The neck, however, is a softer, more malleable stainless steel which adds toughness to the tool while reducing costs.
Interestingly, the blade and neck are not welded together, but are connected by spinning the neck at high speed and forcing it against the stationary blade fusing the two components together more securely than is possible by welding. An amazing sight to see. High-level mechanical engineering going on here, boys and germs.
Standard widths for high-speed steel oiirenomi are 3mm, 6mm, 9mm, 12mm, 15mm, 18mm, 21mm, 24mm, 30mm, 36mm, and 42mm.
“Do not wait; the time will never be “just right.” Start where you stand, and work with whatever tools you may have at your command, and better tools will be found as you go along.”
The oldest style of oiirenomi currently available nowadays is called ” kakuuchi oiirenomi” （角打追い入れ鑿）which means ”square-forged oiirenomi,” refering to the squarish shape. In cross section, the blade is rectangular with 4 more-or-less square outside corners. Other than this cross-sectional detail, it is identical in appearance to the mentori oiirenomi we discussed in my earlier post here.
Where the Shinogi Oiirenomi in the previous post is thin and light, the Kakuuchi Oiirenomi is more bulky and heavy. They are also stiffer in the blade and even in the neck, which can be an advantage in narrower widths.
This added stiffness is not due to the extra mass of metal alone, but also to the fact that the steel layer is wrapped further up the blade’s sides than is possible for the thinner beveled sides of the mentori oiirenomi, as you can see in the photos above. Wrapping the high-carbon steel cutting layer up the blade’s softer low-carbon steel sides in this way creates in effect a hardened steel “U” channel with an increased moment of inertia, which makes the blade much stiffer. The thicker the chisel’s sides, the deeper the U channel, and the stiffer the blade.
The U-channel construction of Japanese chisels is a clever but subtle structural detail unique in the universe of chisels and one most people are not aware of.
Carving chisels do not have this U-channel detail and therefore are not as stiff or as tough as chisels that do. When you are considering buying a chisel, this is an important feature to confirm.
Kakuuchi chisels take less time for a blacksmith to shape than the mentori oiirenomi we discussed in Part 2 of this series. The difference in shaping these two styles of chisels is the added step of grinding the extra bevels that make the mentori oiirenomi sleeker.
Indeed, most styles of Japanese chisels can be obtained with a Kakuuchi cross section, including the oiirenomi version shown in my previous post, as well as atsunomi and usunomi, chisels we will examine in future posts.
Kakuuchi-style chisels take a little more effort to sharpen because the area of the bevel is larger, and more significantly, the area of the hard steel layer is greater, but on the other hand, they feel more stable on the stones.
More than a preference for greater weight, stiffness and stability, I suspect most individuals who prefer this old-fashioned chisel are making a fashion statement, something like “brogues not oxfords,” if I can adapt a movie quote.
In my opinion, they are not as elegant in appearance as either the mentori oiirenomi or shinogi oiirenomi referenced in previous posts, but they do have undeniable dignity and presence.
“The best investment is in the tools of one’s own trade.”
The next variety of oirenomi we will look at is called the ”shinogi oiirenomi” (鎬追入鑿).
Shinogi (鎬) means ”ridge” as in the angled ridge of a rooftop or mountain. It is pronounced “she-noh-gee.” I believe the word was borrowed from the sword world where it refers to an angled ridge design on the back edge of Japanese swords (shinogizukuri 鎬造り). This detail is used not only in tatakinomi but in tsukinomi as well.
Shinogi oiirenomi are beveled like mentori oiirenomi but are different in that the bevels extend all the way to the centerline of the blade’s face creating a definite ridge. The thickness of the blade’s right and left edges is typically thinner than oiirenomi making it easier to get into tight corners.
I am very fond of this handy, lightweight style of oirenomi and keep a 10pc set mounted to the inside of my toolchest’s lid.
The downside to this design is that the chisel blade loses some stiffness compared to other styles, so they are less than ideal for heavy-duty wood hogging.
Some call these ” umeki” or ” dovetail” chisels. Indeed, some blacksmiths will grind the bevels to a very thin edge for this purpose.
My blacksmiths will not create these thin edges for three reasons: First, shinogi oirenomi are not all that rigid to being with, and thinning the sides further is inviting breakage. Second, warpage is especially difficult to control in thin cross-sections resulting in more rejects and increased costs. And third, people always cut themselves badly using chisels with sides made thin enough to actually fit dovetails. Neither my blacksmiths nor I want that responsibility.
Most umeki chisels do not have the thin sides most people expect.
If you need very thin, sharp sides, you should grind and polish the bevels yourself. Don’t forget to keep a first-aid kit close by, one you can use with just one hand. Seriously.
Shinogi oiirenomi are available in the same widths as oiirenomi.
In the next post I will introduce an old-fashioned but still useful oiirenomi called the “kakuuchi oirenomi.” Stay tuned.
“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!?!”
This post contains information for the Beloved Customers of C&S Tools to reference when setting up their new chisels. While you don’t have to do it before giving your chisels a ride around the block, performing these setup procedure is essential to ensure your chisel’s handles will endure hundreds of thousands of hammer blows and provide trouble-free service for many decades. Please, don’t put it off.
Which Chisels Require Setup?
There are several general categories and many types of Japanese chisels. I will delve into this subject in great detail in future posts, but the two general classifications are Tatakinomi (叩鑿）meaning “striking chisel,” which are designed to be motivated with a steel hammer to cut larger quantities of wood, and Tsukinomi (突き鑿), which translates directly to “thrusting chisel,” the equivalent of “paring chisel” in the Western tradition, and are designed to be pushed by hand for paring operations. The setup measures described herein are not entirely irrelevant, but are normally unnecessary for tsukinomi.
Tatakinomi, including oirenomi (bench chisels), atsunomi (oirenomi on growth hormones), and mukomachinomi (m0rtise chisels) are the focus of this post.
Steel hammers are not gentle, so takinomi always have steel hoops or crowns on the end to reinforce the handle and prevent them from cracking and splitting. This crown, as well as the ferrule installed at the blade end of the handle (kuchigane) can be highly stressed in use and failure can occur with unpleasant results. In this post I will explain how to setup your tatakinomi to ensure they are happy and provide you excellent service for many decades of hard use.
Why Should I Setup My Chisels?
C&S chisels are professional-grade tools each hand-forged by a single blacksmith in the traditional manner from plain, pure, high-carbon Shirogami steel. They are not mass-produced consumer-grade tools and will serve you best if you treat them in a professional manner.
Japanese tatakinomi chisels are designed and manufactured assuming the end user will perform some setup work before using them. Performing setup will probably help your chisels perform a little better and will absolutely ensure the handles last longer. And by avoiding the deformation and damage that typically develops without proper setup, you will preserve your reputation as a professional woodworker in the eyes of other professionals.
The chisel shown in the photographs in this post is a variety of tatakinomi called an Atsunomi, written 厚鑿 in Chinese characters and which translates to “thick chisel.” Not a romantic name, but certainly accurate at least in comparison to the smaller, more common oirenomi. It is intended for heavier work such as timber framing. I chose it for this blog post because it is easier to photograph.
This chisel was forged by a famous Japanese blacksmith named Shimamura Kosaburo (RIP) who used the brand Kiyotada, meaning “pure and faithful.” During his lifetime Mr. Shimamura was lauded by experts in the fields of blacksmithing and metallurgy as the finest chisel blacksmith in Japan.
Does Chisel Setup Help?
Unlike western chisels, Japanese tatakinomi chisels are designed to be struck with a steel hammer. These impact forces tend to make the handle mushroom and split, but the crown (hoop) contains and compresses the wood fibers preventing this damage. Even then, however, the force of impact does crush and break fibers at the handle’s end so that after decades of use the handle will gradually become shorter.
For the crown to continue to protect the handle properly, it must be able to travel down the handle in tiny increments without gouging and splitting the handle. Also, your hammer may occasionally strike a bit off-center mushrooming the end of the metal crown over time and preventing it from traveling down the handle. If this deformation becomes too great, the mushroomed crown will dig into the handle damaging and weakening it. The crown must therefore be chamfered to prevent deformation and to allow this travel to occur without gouging and splitting the handle
The truncated metal cone or ferrule that fits between the handle and blade is called the kuchigane (口金), which translates to “mouth hardware.” It serves to keep the hammer impulse forces from splitting the handle, but if it does not fit tightly, or if it digs into the handle, it can weaken it, so the wide end of the kuchigane must be deburred and chamfered. In some cases, the handle may need to be shaved to properly accept the kuchigane. The following pictures show what these measures will help avoid.
Tools and Materials
Fine point marking pen or ball pen
Sharp knife for cutting wood
Sharp knife or deburring tool for deburring and chamfering mild steel (an inexpensive kiridashi kogatana with an edge sharpened to 45 degrees shaves metal faster and cleaner than a file)
Rat-tail file or chainsaw file (can also be used for deburring)
Flat mill file
Block of hardwood for driving off crowns
Wet/Dry sandpaper (220, 320, 600 grit)
Satin varnish or polyurethane and thinner
Gas stove or propane torch (optional; outdoors use)
Silk cloth (optional)
Step 1: Safety first. You will need all your fingers for this process. Tape some cardboard around the cutting edge so they remain attached to your hands.
Step 2: Remove the crown (hoop). Grip a block of hardwood tight against the handle, with one end butting up against the crown. Strike the opposite end with a hammer. Work the block around the crown and repeat until the crown comes off.
Step 3: Mark the blade’s orientation on handle. Place a mark or arrow on the end of the handle in line with the flat of the blade to help you reassemble the handle in the same orientation. If you are setting-up multiple chisels at the same time, write the blade width on the handle’s end to avoid confusion later.
Step 4: Separate the blade from handle. If the process of removing the crown did not loosen the blade, hold the blade in one hand and strike the kuchigane against the corner of a wooden workbench or block of wood. The best locations to strike the kuchigane are at points in line with the corners of the square tang, as seen in the photos of the bare tange below. Notice how the tang’s flats are aligned with the top and bottom of the blade.
Strike each corner twice, then shift the point of impact 90° and repeat. The goal is to gradually rattle the handle off, so don’t be shy. If the blade and handle still refuse to separate, expand the kuchigane and shrink the wood using a heat gun or by placing the kuchigane nearly (but not quite) touching a hot incandescent light for a few hours. Do not place the chisel in an oven!
Step 5: Disassemble the handle and kuchigane. If you are setting-up multiple chisels at the same time be sure to keep each chisel’s components separate and mark them.
True the Tang and Shoulder
Step 6: The tang and neck/shoulder should meet at a clean 90° angle (although a slight filet is acceptable), and the shoulder should be clean and flat. If necessary, true it up carefully with a flat file. At the same time, flatten and smooth the shoulder, but be careful to only true the shoulder and not file gouges into it. Also use the file to remove burrs and gross irregularities on the tang as necessary.
As you can see in the photo above, the tang does not need to be perfect, just free of big irregularities and burrs that might cause the fit between handle and tang to lossen after hard pounding,
When you are done, there should not be a pronounced gap between the shoulder and kuchigane when the chisel is assembled.
Prepare the Kuchigane(Ferrule)
Step 7: Check the blade end of the handle with the kuchigane in place. If it is a sloppy fit, adjust the handle using knives, files, and sandpaper as necessary.
Step 8: Flatten each end of the kuchigane with a flat file. Be sure the ends are in planes perpendicular to the kuchigane’s centerline
Step 9: Chamfer the inside of the kuchigane’s wide end (not narrow end) with a knife or round file. Shave or file a a 45° chamfer 1/2 to 2/3 the thickness of the kuchigane’s wall on the inside corner of the kuchigane’s wide end. An inexpensive kiridashi kogatana knife or deburring tool with a blade angle of around 40 degrees will easily shave the mild steel used for crowns and kuchigane and works quicker and cleaner than a file.
A stopped hole drilled into a board works well to secure parts when deburring and chamfering them. Vise grips also work well for securing crowns if you pad the jaws to keep them from gouging the parts, but tend to deform kuchigane
Just be careful not to cut yourself. They may be beautiful and very useful, but many chisels and knives are cold vampiric geniuses (genii?) that fear neither sunshine nor spaghetti sauce and want to cut you, so beware! Hold parts in a way the blades absolutely can’t bite you no matter how hard they try. A severed tendon can be a tragic life-changing injury.
Step 10: If you decide to refinish the kuchigane, remove the existing chemical bluing with sandpaper at this time.
Prepare the Crown(Hoop)
Step 11: Chamfer both inside corners (top and bottom edges) 45° with a knife or a rat tail file. This step is very important.
Step 12: Deburr and clean up the crown’s inside surface. However, be careful to not remove too much metal or the crown may fit too loosely.
Step 13: Lightly file and sand the crown’s exterior surfaces to remove major irregularities. There is little point in trying to make these surfaces perfectly smooth since they will get banged up by hammers.
Prepare the Handle
Step 14: Check the Depth of the Tang Hole. If this hole is too shallow, the pointy end of the tang will bottom-out and can cause the handle to split. Measure it with piece of wire or a stick. If it is not deeper than the length of the tang, drill the hole just a tad deeper.
Step 15: Check/Adjust Blade Alignment. With the kuchigane removed, insert the tang into the handle correctly oriented, and sight down the handle. If the handle and blade do not line up properly, you may need to correct the misalignment.
To do so, first try fitting the blade to the handle in a different orientation (90˚). If this does not improve things, make thin slips of wood the width of the tang’s flat and fit one into the hole before inserting the blade. Slips made of cardstock, manila folder, or cotton typewriter paper work well too. If you feel a lot of resistance when inserting the tang, attach the kuchigane to prevent splitting.
Thinner or thicker slips can be inserted if more correction is necessary, but there is a point where too many slips will make it impossible to insert the tang without splitting the handle. In this worse case scenario, shave the hole a bit wider with a chisel or other slender piece of steel sharpened as a scraper to permit adequate shimming. Be careful to remove the absolute minimum amount of wood.
Step 16: Check/Adjust Crown Fit. It is acceptable for the crown to leave a shallow ring depression in the handle, but if the crown digs deeply into the handle, shave or sand the handle to ensure the crown will not gouge it.
Step 17: Prep the Shoulder. Most chisels have a shoulder turned into the handle where the kuchigane terminates, making for a smooth, attractive transition between kuchigane and handle. This is most pronounced in chisels made in Western Japan. However, if the kuchigane butts tight up against this shoulder, over time the force of the hammer can drive the kuchigane into this shoulder damaging the handle.
Relieving this shoulder with scallops will provide some room for smooth movement of the kuchigane over time. To do this, first mark a line around the handle where the kuchigane ends. Then remove the kuchigane.
Step 18: Wrap a piece of paper or light cardboard 3/16″ to 1/4” above this line, secure it with tape, and using it as a guide, mark another line around the handle with a fine-point marking pen, ball pen, or knife. Remove the kuchigane and paper.
Step 19: Mark the Handle: Use a pen, pencil or marking pen to mark the cone at diagonals across the tang hole and extend these marks to the line you made in the previous step. This will leave four lines 90° apart. Now make similar marks at the flats of the tang and extend the lines. There should now be eight lines separated by 45°.
Step 20: Cut the Scallops: Wrap masking tape around the cone as shown in the picture below to protect the cone from cuts which might weaken it. With a very sharp knife, make four cuts in small increments centered on one of the lines and forming a concave scallop between the two adjacent lines. Repeat for the other four lines. These curved scallops should transition smoothly into the wooden cone, but should not cut into it. This may not be as easy to accomplish as it seems. If done properly, the scallops should appear very uniform and attractive. Finally, shave off the ridge between the scallops creating a total of sixteen scallops at 22.5°.
Finish the Handle
Some people prefer a handle without any finish, while others like a shiny finish.
Hand sweat tends to react with the tannic acid in Japanese White Oak handles turning them a dirty-looking grey. Japanese Red Oak, as in the handle in the pictures above, does not discolor as much.
Whether you refinish the handle, leave it as-is, or sand it bare is your choice. It makes no difference to the chisel’s performance.
Step 21: Sand the Handle. So at this point, you can either (1) Not sand the handle (unless it is damaged), and varnish the scallops and any areas shaved at the crown end of the handle to match the existing handle finish; (2) Sand off the existing finish entirely to bare wood; or (3) Refinish the entire handle.
Step 22: Apply a Finish: This step is applicable if you decide to apply a finish to the handle. Sweat may cause Japanese White Oak, a wood commonly used for chisel handles, to discolor, so a light finish (not a thick glossy finish) is appropriate in my opinion. The following is the method I recommend. First, sand off any remaining finish on the handle. Apply a coat of satin varnish or polyurethane diluted 100% with thinner. Allow as much of this mixture to soak into the wood’s fibers as possible. Rub the wet varnish mixture forcibly into the wood using wet-or-dry sandpaper. Thinned varnish will penetrate further into the wood than straight varnish, and the pressure of sanding will force it deeper into the fibers than just capillary action. In addition, sanding will create a wood/varnish slurry filling the grain.
Allow this mixture of varnish and wood dust to dry without wiping it off. It will look terrible, but never fear. Repeat these steps for a second coat and allow to dry. Apply a third coat, sand lightly, and then wipe off the varnish slurry with a cloth.
When dry, the result will be a non-slip surface free of lathe marks that does not appear to have any finish, but that will protect the wood from sweat and moisture. If a little bit of visible surface finish is desired, a final single coat of thinned varnish can be applied. To ensure the previously cut scallops remain nice and crisp, do not sand them.
Warning: Do not apply finish to the crown end of the handle because the finish will make the wood fibers too stiff to deform properly. If you want to go the extra mile, a bit of melted paraffin wax or beeswax allowed to soak into the end of the handle will protect it from water and make it more resilient over time than just bare wood.
Finish the Kuchigane and Crown
This is an optional cosmetic step, but will make your chisel more attractive. There are several ways of surface finishing the metal of the kuchigane and crown:
Heat Bluing: Simply heat the kuchigane and crown on a stove until it is blue-black. Not very durable.
Oil Black: Coat the metal with motor oil and heat it until the oil is burnt off. This method makes a lot of stinky smoke, so don’t do it indoors. Fairly durable.
Gun Blue (chemical bluing): Brownells’ cold blue formula works well. Birchwood Casey also makes a convenient chemical bluing product. Looks nice, but not very durable.
Rust Blue or Rust Black: These are classic, beautiful gun metal finishes that are much more durable than chemical or heat bluing. However, the process requires dangerous chemicals and time. A description of the process is not possible here. Extremely durable.
Burnt Silk Finish: This is my favorite finishing method because it is quick and easy and looks good. Simply heat the metal parts over a flame, and using pliers so you don’t burn yourself of course, wipe the metal in a wad of scrap silk. An old silk necktie works fine. The silk protein will char, coating the metal with a carbon finish with an interesting texture. Wipe the metal quickly but thoroughly to prevent globs of melted silk from sticking to the metal. Don’t do this inside the house because the smoke will set off the smoke alarm and the stink will endure for weeks. SWMBO will not be pleased.
Reassemble the Chisel
If this is a new chisel, it may be convenient to sharpen the blade before final assembly.
Step 23: Install the Crown. To begin assembly, hold the handle in the air by one hand and drive on the crown using a mallet, not a steel hammer. You should always remove your wrist watch before wacking chisels, and now is a good time too.
There is a specialty tool for this job, essentially a steel cone that fits over the crown, which you strike with a hammer. If you enjoy spending money on heavy tools that take up space and are seldom-used, then you gotta have one. But a wooden mallet works just as well and can do many more tasks.
Once the crown is flush with the handle, angle the handle and strike the crown with your mallet driving it further onto the handle. It only needs to be driven down so the top of the crown is below the end of the handle by 1/16”. More is wasteful. Then use a steel hammer to lightly mushroom over the corners of the handle securing the crown in place. Do not soak the handle in water.
Soaking the handle in water prior to fitting the crown is a method preferred by handlemakers and wholesalers that fit hundreds of crowns a day. They will soak 50 handles at a time in a shallow pan of water to make the wood softer and easier to deform. The problem with this technique is the water will also cause the wood to swell, and when it later dries and shrinks, the crown may become loose over time. Your handle deserves better.
Step 24: Install the Kuchgigane. Fit the kuchigane to the handle lightly and insert the blade’s tang oriented according to the marks you made previously. Tap the end of the handle to lightly seat the blade, but allow enough room so the kuchigane can be rotated by hand. Rotate the kuchigane to minimize any gaps between it and blade’s shoulder. If you see any big gaps, lightly file the kuchigane to match the blade’s shoulder. If any part of the handle projects past the kuchigane’s mouth, carefully shave it off with a sharp knife.
Step 25: Seat the Blade. Finish seating the blade by holding the chisel in your hand in the air and striking the end squarely with a steel hammer until it seats tightly.
Use the Right Hammer
When cutting wood, please use a hammer with a flat face, such as a Japanese gennou, to strike your chisel. A hammer with a domed or convex face, as are almost all hammers sold outside Japan nowadays, will damage the chisel’s handle after enough strikes. Ergonomics aside, a ball peen hammer or claw hammer with its face ground flat will work just as well as a Japanese gennou.
And while we are on the subject of hammer faces, I recommend you smooth and even polish your hammer face so it will strike cleaner and reduce the wear on your chisel handles, counterintuitive as that may seem. Slipping will not be a problem, trust me.
I encourage you select a hammer weight that balances well with the weight and blade width of your chisel, the type of wood and type of cutting you plan to do, and your body and style of work. This decision will make a difference in the precision and speed of your work, the energy you expend, and the stress on your joints.
375gm (13.2 ounces) is a standard medium weight for gennou hammers in Japan, perfect for driving nails, general carpentry work, and motivating atsunomi. However, many find a lighter-weight head, perhaps in the neighborhood of 80~60 monme (300gm/11 oz to 236gm/ 8.3 oz), works better with smaller chisels, such as oirenomi, for furniture and joinery work.
I also encourage you to make a handle for your hammer that suits your body and style of work.
This post is already too long so I won’t go into details, but suffice it to say that commercial hammer handles are a one-size-fits-nobody design that confuses the hand, is un-aerodynamic (I bet you never thought about air-drag in relation to hammer handles), transmits excess vibration to your joints, and ignores obvious ergonomics causing the head to impact the chisel off-center and out-of-kilter. There is a better way, and you will love the results.
But we will dive head-first down that rabbit hole in future posts.
Rust Prevention & Storage
If set up properly, a quality set of Japanese chisels will endure decades of hard daily use with no maintenance beyond oiling and sharpening.
You should store your chisels where they will be protected from weather, water, sudden temperature changes, dust, fly-specs, and paint overspray. Convenient though it may be store chisels in an exposed rack or bare on a shelf, unless you use chisels stored this way nearly everyday and clean and oil them frequently, such storage methods reduce their useful lifespan and will waste your sharpening efforts and sharpening stones sure as eggses is eggses.
I recommend you make a wooden chisel box with a lid to store your chisels. I am preparing an article on how to design and make a chisel box, and will post it on the blog when it is ready.
After every use, oil the blade to prevent rust. An aburatsubo or oilpot is a critical accessory for chisels, and is easily made. You can find details here.
PS: If you have questions, please use the form below. Your information will remain confidential (we’re not evil Google or incompetent facebook).