“The beginning of wisdom is to call things by their proper name.”
The “Tsuba” in Tsuba Nomi is the Chinese character 鍔 which means “guard” as in a sword or knife guard.
Two nubs attached to opposing sides of the blade just below the handle look like the guard for a knife or sword. This chisel is driven with a hammer to quickly create a pilot hole for nails or screws. The blade becomes tightly wedged into the wood, but by striking up on these projections with a steel hammer, the blade can be extracted.
This unique chisel comes with blades with round, square, or rectangular cross-sections.
Square and rectagular blades usually have a chisel-point beveled on two sides, but sometimes are beveled on just one side. Round blades may have simple pointed ends, but sometimes they have short triple tines to drive the crushed wood fibers into the hole.
While this chisel severs the wood fibres, unlike an auger, drill, or gimlet, it does not remove material from the hole. The ends of the severed fibers are angled down into the hole, and over time and exposure to humidity and water, will partially swell back to their original shape locking nails in tightly.
This chisel is still used in the wooden shipbuilding industry, but other than that sees very little practical use nowadays. I own one but have have never used it in anger.
“There is a great satisfaction in building good tools for other people to use.”
This is the second and final post about the heavy-duty Japanese carving gouges.
The Sotomaru Nomi” 外丸鑿 is what is called an “Incannel Gouge” in the West. “Soto” 外 means “outside” or “external,” “maru” 丸 means “round,” and “nomi” 鑿 means “chisel.” The name corresponds closely to the English language term for incannel gouges.
As with other Japanese chisels, the Solomaru nomi has a thin layer of high-carbon steel laminated to a softer low-carbon steel body with a neck and tang. They also have the ferrule which compresses the handle’s wood to keep the blade’s tang firmly attached to the handle and prevent the handle from splitting, and a crown to prevent the handle from cracking when struck with a steel hammer. Unlike most Japanese chisels, however, they do not have a hollow-ground ura.
The cutting edges differ from their Western counterparts in that the bevel is a single, flat plane, instead of a curved surface. The advantage of this detail when sharpening would be difficult to overstate. The blade can be sharpened on a normal, flat sharpening stone without pesky slips, finger contortions, or heaven forfend, miniature die grinders.
This is an unusual chisel outside Japan, but is indispensable for working round wood and bamboo used in Japan’s sukiya and teahouse construction traditions. Although this chisel has many advantages, it will not waste wood as rapidly as the uchimaru chisel we looked at in the previous post. Its shape is more conducive to cutting precisely curved surfaces than its concave sisters.
The hard steel lamination in this chisel has more support than its brother the uchimaru gouge we looked at in the previous post, making it a bit tougher.
Sharpening is easier and quicker than other gouges because the bevel can be treated as a single flat plane. The area called the “flat” or “ura” on conventional chisels is convex so it can be worked on a flat stone eliminating entirely the need for those pesky grooved stones and slips.
The disadvantage is that the flat bevel/curved cutting edge cannot make clean stopped cuts against 90 degree surfaces. This shortcoming is easily dealt with, however, by making a few more passes.
The sotomaru nomi is perfect for fitting straight line curved surfaces in some situations because its convex surface can ride and index directly on the concave surface being shaped, whereas the more common concave gouge must be tilted at an angle on its axis to cut, with less precision.
Since this chisel can cut parallel to its axis, and does not need to be angled up from the surface being worked to cut, it can cut and carve in much tighter locations than standard gouges.
If you need to make curved cuts at 90° to the workpiece’s surface, as in the photos above, then this chisel is indispensable. I’m sure you can see why this chisel is a must-have for the elegant ” round work” the Japanese love so much.
Another advantage is that the sloped cutting edge can easily make undercuts, something their Western counterpart cannot do. This is an essential performance criteria for accomplishing a few traditional Japanese architectural details such as the edge detail in the beam nose shown in the photo below. Good luck cutting that with a standard gouge!
It’s always nice to have the right tool for the job at hand.
Standard sizes are 9mm, 12mm, 15mm, 18mm, 24mm, 30mm, 36mm, and 42mm.
“Along with the milk of my nurse I received the knack of handling chisel and hammer, with which I make my figures.”
In a previous post, we looked at various types of oiirenomi (bench chisels) and mortise chisels. In this post we will examine a type of tatakinomi called the “Atsunomi.”
The ”Atsunomi, ” written 厚鑿, translates to “thick chisel.” This is the largest variety of tatakinomi and is almost identical in design to its petite oirenomi sisters. Being larger, heavier and stronger it is able to transmit and endure the impact forces of heavy hammer blows from sunup to sundown and cut a lot of wood. Indeed, I can remember times when the handles of the 24mm and 30mm Kiyotada atsunomi in the photographs on this page became seriously hot after long hours of heavy hammer blows.
The 24mm chisel in the photograph below was the first atsunomi I owned. All three of the Kiyotada atsunomi chisels shown herein have seen hard use with heavy hammers, but have held up well.
If I can liken the bench chisel or oiirenomi to a 1/4″ cordless hand drill, then the atsunomi is a 9 amp 1/2″ corded drill (when combined with the right steel hammer). Serious business indeed.
The atsunomi is ideal for heavy work such as timber framing and wasting large amounts of wood quickly. However, carpenters are not the only trade to use them. Many professional craftsmen in Japan, even those that never work on construction sites, prefer to use atsunomi even for delicate work because of their relatively longer blades, greater durability, and cost-effectiveness.
Because of its greater size and weight, the atsunomi is not as nimble as the smaller varieties of tataki nomi and demand greater strength and skill of the user. But on the other hand, it is very stable in the cut and wastes wood with oodles of gravitas.
As with all tataki nomi, the handle is big enough to use with one hand, but not two. Atsunomi always have a mild steel katsura crown installed at the end of the handle to reinforce it and prevent it from splitting under hammer blows.
Standard widths for atsunomi are: 12㎜, 15㎜, 18㎜, 21㎜, 24㎜, 30㎜, 36㎜, 42㎜, 48㎜.
There are several varieties of atsunomi, some with very wide blades and others with very long necks, but I will not go into that level of detail in this post.
In Part 9 of this saga of romance and derring-do, we will examine the Uchimaru Nomi.