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 21mm (Left Face View)
Kiyotada Kotenomi 21mm (Face View)
Kiyotada Kotenomi 21mm (Ura View)
Kiyotada Kotenomi 21mm (Right Shoulder View)
Kiyotada Kotenomi 21mm (Face View CU)

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.

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).

Kiyotada Kotenomi 9mm (Face View)
Kiyotada Kotenomi 9mm (Ura View)
Kiyotada Kotenomi 9mm (Right Side Neck View)
Kiyotada Kotenomi 9mm (Left Side View)

Kiyotada Kotenomi 9mm (Left Face View)

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.

Standard kotenomi chisel (face view)
Standard kotenomi chisel (Right 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

Links to Other Posts in this Series

The Varieties of Japanese Chisels Part 1 – The Main Categories

The Varieties of Japanese Chisels Part 2 – The Mentori Oiirenomi (面取追入鑿)

The Varieties of Japanese Chisels Part 3 – The Shinogi Oiirenomi (鎬追入鑿)

The Varieties of Japanese Chisels Part 4 – Kakuuchi Oiirenomi (角打追入鑿)

The Varieties of Japanese Chisels Part 5 – High-Speed Steel Oiirenomi (HSS 追入鑿)

The Varieties of Japanese Chisels Part 6 – The Mortise Chisel (Mukomachi Nomi 向待鑿)

The Varieties of Japanese Chisels Part 7 – The Nihon Mukomachi Nomi (二本向待鑿)

The Varieties of Japanese Chisels Part 8 – The Atsunomi (厚鑿)

The Varieties of Japanese Chisels Part 9 – The Uchimaru Nomi Gouge (内丸鑿)

The Varieties of Japanese Chisels Part 10 – The Sotomaru Nomi Incannel Gouge (外丸鑿)

The Varieties of Japanese Chisels Part 11 – The Tsuba Nomi Guard Chisel (鍔鑿)

The Varieties of Japanese Chisels Part 12 – The Usunomi Paring Chisel (薄鑿)

The Varieties of Japanese Chisels Part 13 – The Shinogi Usunomi 鎬薄鑿 Paring Chisel

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

If you have questions or would like to learn more about our tools, please use the questions form located immediately below. Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google or incompetent facebook and so won’t sell, share, or conveniently and profitably “misplace” your information.

The Varieties of Japanese Chisels Part 4 – Kakuuchi Oiirenomi (角打追入鑿)

“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.”

George Herbert

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.

Kakuuchi Oiirenomi – Hidari no Ichihiro (Hyotan mark)
Kakuuchi Oiirenomi – Hidari no Ichihiro (Polished; Hyotan mark)
Kakuuchi Oiirenomi – Hidari no Ichihiro (Hyotan and “Mi” marks)

DESCRIPTION

Where the Shinogi Oiirenomi in the previous post is thin and light, the Kakuuchi Oiirenomi is bulkier and heavier. 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, and the deeper the U channel, the stiffer the blade will be.

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.

The following are some pictures of two of our Kakuuchi Oirenomi by Nagamitsu, hand-forged, of course, from Hitachi Yasuki Shirogami No.1 Steel (aka “White Steel).

36mm Kakuuchi Oiirenomi by Nagamitsu (Face)
36mm Kakuuchi Oiirenomi by Nagamitsu (Side)
12mm Kakuuchi Oiirenomi by Nagamitsu (Ura)
36mm Kakuuchi Oiirenomi by Nagamitsu (face)
36mm Kakuuchi Oiirenomi by Nagamitsu (Side)
36mm Kakuuchi Oiirenomi by Nagamitsu (ura)

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 nor as handy as either the mentori oiirenomi or shinogi oiirenomi referenced in previous posts, but they do have undeniable dignity and presence.

What do you think?

YMHOS

Links to Other Posts in this Series

The Varieties of Japanese Chisels Part 1 – The Main Categories

The Varieties of Japanese Chisels Part 2 – The Mentori Oiirenomi (面取追入鑿)

The Varieties of Japanese Chisels Part 3 – The Shinogi Oiirenomi (鎬追入鑿)

The Varieties of Japanese Chisels Part 5 – High-Speed Steel Oiirenomi (HSS 追入鑿)

The Varieties of Japanese Chisels Part 6 – The Mortise Chisel (Mukomachi Nomi 向待鑿)

The Varieties of Japanese Chisels Part 7 – The Nihon Mukomachi Nomi (二本向待鑿)

The Varieties of Japanese Chisels Part 8 – The Atsunomi (厚鑿)

The Varieties of Japanese Chisels Part 9 – The Uchimaru Nomi Gouge (内丸鑿)

The Varieties of Japanese Chisels Part 10 – The Sotomaru Nomi Incannel Gouge (外丸鑿)

The Varieties of Japanese Chisels Part 11 – The Tsuba Nomi Guard Chisel (鍔鑿)

The Varieties of Japanese Chisels Part 12 – The Usunomi Paring Chisel (薄鑿)

The Varieties of Japanese Chisels Part 13 – The Shinogi Usunomi 鎬薄鑿 Paring Chisel

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

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

If you have private questions or would like to learn more about our tools, please use the questions form located immediately below. Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” Your information will remain confidential (we’re not evil Google or incompetent facebook).

The Varieties of Japanese Chisels Part 3 – The Shinogi Oiirenomi (鎬追入鑿)

“The best investment is in the tools of one’s own trade.”

Benjamin Franklin

The next variety of oirenomi we will look at is called the ”shinogi oiirenomi” (鎬追入鑿).

Hidari no Ichihihiro Shinogi Oiirenomi Blade
Shinogi Oiirenomi – Nagamitsu 長光

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.

鎬が高い図
Two Angles of Sword Shinogi
日本刀の断面図
Blade Cross-section
View of Sword’s Shinogi and Hamon

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.

YMHOS

© 2019 Stanley Covington All Rights Reserved

Links to Other Posts in this Series

The Varieties of Japanese Chisels Part 1 – The Main Categories

The Varieties of Japanese Chisels Part 2 – The Mentori Oiirenomi (面取追入鑿)

The Varieties of Japanese Chisels Part 4 – Kakuuchi Oiirenomi (角打追入鑿)

The Varieties of Japanese Chisels Part 5 – High-Speed Steel Oiirenomi (HSS 追入鑿)

The Varieties of Japanese Chisels Part 6 – The Mortise Chisel (Mukomachi Nomi 向待鑿)

The Varieties of Japanese Chisels Part 7 – The Nihon Mukomachi Nomi (二本向待鑿)

The Varieties of Japanese Chisels Part 8 – The Atsunomi (厚鑿)

The Varieties of Japanese Chisels Part 9 – The Uchimaru Nomi Gouge (内丸鑿)

The Varieties of Japanese Chisels Part 10 – The Sotomaru Nomi Incannel Gouge (外丸鑿)

The Varieties of Japanese Chisels Part 11 – The Tsuba Nomi Guard Chisel (鍔鑿)

The Varieties of Japanese Chisels Part 12 – The Usunomi Paring Chisel (薄鑿)

The Varieties of Japanese Chisels Part 13 – The Shinogi Usunomi 鎬薄鑿 Paring Chisel

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

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

If you have private questions or would like to learn more about our tools, please use the questions form located immediately below. Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” Your information will remain confidential (we’re not evil Google or incompetent facebook).

Setting Up Japanese Chisels

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 perform this process before giving your chisels a ride around the block, these setup procedures are essential to ensure your chisel’s handles will endure hundreds of thousands of hammer blows and provide trouble-free service for many decades. They may also help your chisels perform more efficiently. Please, don’t put it off too long.

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 steroids), and mukomachinomi (mortise 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, so we highly recommend the proper setup of these kinds of chisels.

Why Should I Setup My Chisels?

C&S chisels are professional-grade tools, not mass-produced consumer-grade tools. They will serve you best if you treat them in a professional manner, including performing proper setup.

In fact, Japanese tatakinomi chisels are designed and manufactured assuming the end user will perform some setup work before using them. This is traditional. It was not that long ago that craftsmen in Japan purchased chisels as components and made the handles themselves.

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 article 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. I agree with the assessment.

Kiyotada Brand Atsunomi Chisel in brand-new unused condition prior to setup

Unlike western chisels, Japanese tatakinomi chisels are designed to be struck with a steel hammer. These impact forces tend to cause the handle to mushroom and even 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 over decades of hard use the handle will gradually become shorter.

For the crown to continue to protect the handle properly as it becomes gradually shorter, the crown must be able to travel down the handle in tiny increments without gouging and/or splitting the handle. Also, your hammer may occasionally strike a bit off-center mushrooming the crown over time preventing it from traveling down the handle without gouging. In order for the crown to continue to protect the handle from splitting, it must therefore be chamfered to prevent deformation and to allow this travel to occur without gouging 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 metal.” This bit of hardware is key to the handle design of Japanese chisels because it serves to keep the hammer impulse forces from splitting the handle by compressing the handle against the tang. But if the kuchigane 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.

Split Handle
Mushroomed Crown and Handle Crack

Tools and Materials Needed for Performing Setup

  • Masking tape
  • 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
  • Pliers
  • 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)

Disassembly

Mark Orientation of Handle to Blade

Step 1: Safety first. You will need all your fingers for this process, and icky red stuff will make the handle slippery, so please tape some cardboard around the cutting edge to ensure your digits remain attached to your hands.

Step 2: 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 or other designation on the handle’s end to avoid confusion later.

Step 3: 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 tang 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!

Rap the Kuchigane to separate it from the handle and tang. You can see the gap at the top of the kuchigane where it is beginning to separate from the handle.

Step 4: Remove the crown (hoop). Now that the blade and handle are separated, 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.

Remove the Crown
A view of the end of the handle where the crown was previously installed. Notice the compression lines produced in the wood when the crown was first installed. The inside of the hoop needs to be cleaned up and the end chamfered to prevent the hoop from gouging the handle, obviously, but this sort of tight fit is desireable.

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. I usually write the blade’s width on the handle’s end with a marking pen and scratch it inside the kuchigane and crown with a pointed ascribe or awl.

The Chisel’s Four Component Parts

True the Tang and Shoulder

Step 6: True the Tang and Shoulder: Perfection is not necessary. The tang and neck/shoulder should meet at a clean 90° angle, however a slight filet is acceptable. The shoulder should be clean and flat. If necessary, true it up carefully with a flat file, but be careful to only true the shoulder without filing gouges into the tang. Also use the file to remove burrs and gross irregularities on the tang as necessary. Please remember that the tang will always be hidden, so please don’t weaken it by trying to file it to perfection.

The tang before cleanup
The tang after cleanup

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 loosen 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 Kuchigane: 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 the End of the Kuchigane: Flatten each end of the kuchigane with a flat file. Be sure the ends are in planes perpendicular to the kuchigane’s centerline

Kuchigane before chamfering

Step 9: Chamfer the Kuchigane: 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 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.

Kuchigane after chamfering

Step 10: Refinish the Kuchigane: If you decide to refinish the kuchigane, remove the existing chemical bluing with sandpaper at this time.

Prepare the Crown (Hoop)

The Crown Before Deburring and Chamfering

Step 11. Chamfer the Crown: Chamfer both inside corners (top and bottom edges) to a nice round 45° angle with a knife or a rat tail file. This step is very important.

The crown after chamfering. This step is critical.

Step 12. Deburr the Crown: 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.

Deburred, Chamfered, Filed and Sanded Crown

Step 13: Clean the Crown’s exterior surfaces: 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 the hole in the handle which receives the tang is too shallow, the pointy end of the tang will bottom-out and can cause the handle to split. Measure it’s depth 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.

The Handle’s Coned End Before Fitting

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. Place a Guide Around the Handle: Wrap a piece of paper or light cardboard 3/16″ to 1/4” above the line of the shoulder, 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 uniform and attractive. Perfection is neither attainable nor desirable in a handmade tool. 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. Do not heat the blade!

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. Do not heat the blade!

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. Do not heat the blade!

Reassemble the Chisel

If this is a new chisel, it may be convenient to true the blade’s ura and sharpen it before final assembly. These tasks are a little easier with the handle removed.

Step 23: Install the Crown: To begin assembly, hold the handle in the air by one hand and drive on the crown using a wooden, plastic or rawhide mallet, not a steel hammer. You should always remove your wrist watch before wacking chisels if you want it to keep working. A word to the wise.

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 must 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. You only need to be drive it down far enough 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, for Pete’s sake!

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 soften the ends making it easier to mushroom. Convenient for them, but bad for the chisel because 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 Kuchigane: 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 mallet or hammer until it seats tightly.

Voila!

Step 26. Final Check and Adjustment of Kuchigane to Shoulder Fit: Now that the chisel is assembled, there is one last check to make. The fit between the blade’s shoulder and the narrow end of the kuchigane need not be perfect (perfection is unattainable for mere mortals) but it does need to be fairly uniform because most of the impulse energy from the hammer flows through this tiny interface. Therefore, if there is a big gap, or if half the kuchigane on one side, for instance, is not contacting the shoulder, the flow of energy will not be smooth and the chisel will feel “skittish.” Examine this fit for gaps and irregularities, and correct them by filing the kuchigane. You will need to loosen the blade and handle enough to insert a small file, but you don’t necessarily need to completely disassemble the chisel.

Congratulations! Your chisel is now setup for professional use.

Use the Right Hammer

When cutting wood with a tatakinomi, 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, may 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 hardware-store 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 60~80 monme ( 236gm (8.3 oz) to 300gm (11 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.

We will dive head-first down that rabbit hole, screaming like a banshee on fire, in future posts.

Kosaburo Gennou Head and Black Persimmon Handle

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, spilled beer, and paint overspray. Convenient though it may be store chisels in an exposed rack or bare on a shelf, unless your workshop is a temperature and humidity controlled cleanroom, or you use chisels stored this way nearly everyday and clean and oil them frequently, such storage methods are guaranteed to 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.

YMHOS

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