All times are good for those who know how to work and have the tools to do so.
The Ootsuki nomi is the largest of the Japanese chisels. It is essentially a scaled-up tsukinomi paring chisel, equivalent to what is called a “slick” in the West.
The name is written 大突鑿 which is the same as tsukinomi with the addition of the character 大 meaning “large,” or “ big.” Besides “Oo “ this character can also be pronounced “dai.” If you examine this very basic Chinese character you may notice it looks like a man with his legs spread and arms extended, as if he is describing to his buddies the size of the fish that got away. At least that’s how I remembered the meaning when I was a young man in Japan many moons ago.
So the name translates directly to “large paring chisel.”
If you have never done timber framing, a brief explanation may be helpful.
When doing production work (versus hobby stuff) one cuts the pieces and parts of most open joints using circular saws. Handsaws are also necessary for some cuts, but for most situations a circular saw is much quicker and less tiring. There’s a lot of wood that needs cutting after all and only so many hours of daylight.
Mortises are typically cut with portable electric hollow-chisel machines. There are other options such as portable chainsaw mortisers, stationary router machines, or the amazing German Hundegger machines. http://hundeggerusa.com
I once worked for a Japanese company that cut entire structural frames using CAD driven CNC machines in a factory. In that situation however, the CNC machinary, while very precise and very quick, was so expensive and so inflexible that the building had to be designed around the repertoire of joints and sizes the machinary could cut rather than the joints required to make the best building. And it could not handle significant dimensional irregularities in the timbers used, so only machined glulams were suitable. A very limiting endeavor indeed. The sort of frame the gentlemen in the pictures below are cutting was simply impossible for CNC equipmennt. I left that job after 2 years.
Sharp tools guided by human hands, controlled by human minds with years of experience are more flexible.
Indeed, handtools like axes, adzes, chisels and handsaws are necessary especially when doing “ round work” in logs or when the design calls for irregular-shaped timbers. Paring chisels are also needed to achieve the relatively precise tolerances and smooth surfaces such work demands.
Ootsuki nomi are relatively heavier than other Japanese paring chisel with larger diameter and longer handles. They are built to resist the large bending moment forces created by a large man gripping the handle with both hands and pushing like a plow horse to pare wood. This is the task this chisel excels at.
Most Japanese carpenters that use this tool buy them in sets of two: a wide 48~54mm wide one and a narrower 24mm chisel, although other sizes are available. I own a set by Kiyotada, one with a 54mm blade and an extra-large handle intended for working especially large North American timbers.
The wider width of the two in the set is used most frequently for paring tenons and saddles.
The 24mm is used for paring standard rectangular mortise, dovetail mortises and dovetail tenons, besides a hundred other tasks. In cross section, it is essentially a large shinogi usunomi chisel to help it get into tight places.
When paring large surfaces with the wider ootuskinomi chisel the hollow ground ura may allow bumps to escape paring requiring multiple passes to knock them down. This is easy to overcome with practice, but some people prefer an ura with not a single, but multiple grinds with lands between each hollow-ground area to help index the blade. I believe this is one of the few situations where these multiple ura, called mistuura or “triple-ura” are useful.
Some people like the unusual appearance of mitsuura. I must admit they look sexy in wide blades, but they have their downsides . The first downside is that mitsuura blades can take a little longer to sharpen. Second, they can be a little harder to keep flat. Neither of these are difficult problems to overcome. But the third downside is more problematic.
Because the three hollow-ground areas are shallower and have less total volume than a single ura, they tend to wear out and disappear sooner. This is not a serious deficiency unless you use and sharpen a mitsuura chisel a lot, or have a heavy hand when sharpening the ura. The negative impacts are minor in most cases.
I just want you to be aware of these peculiarities and to be gentle when sharpening mitsuura blades.
These are not chisels most people will ever have need of but as long as humans are doing timber framing, there will always be a demand for this unique tool.
Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located immediately below.
You cannot mandate productivity, you must provide the tools to let people become their best.
This post will be a little different from my normal post for several reasons. First, because although I love this tool, I can’t procure them anymore, so it is more of a show and tell. And second, because I have a couple of stories to tell about the blacksmith that made it, and the store that sold it to me.
The kote nomi is written 鏝鑿 in Chinese characters meaning ” trowel chisel.” It is not an elegant name, but is accurately descriptive. It is essentially the same as the Western ” cranked-neck chisel. ” It is used to pare grooves, dadoes, sliding dovetails, rabbits and mortises, anywhere the handle of a regular paring chisel would get in the way.
The sides have a steeper bevel than regular chisels, much like a shinogi usunomi, to help it get into tight places and cut right up against the sides of sliding dovetail groves, dadoes, etc..
These are not easy chisels to sharpen because of both the offset, and the tendency for the neck to get in the way.
This is one of those chisels that you may not need often, but when you do need it, you need it badly.
The shape of the 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.
Pixie, kobold, elf, and sprite,All are on their rounds tonight;In the wan moon’s silver ray, Thrives their helter-skelter play.
Gentle Reader, have you ever placed a tool down, only to later discover it has vanished into thin air? Do your tools ever become unexplainably dull or corroded within what seems like just a few days after cleaning and sharpening them? If so, you may have an Iron Pixie infestation without realizing it.
Respected fairyologists theorize that, unlike their timid brethren frolicking in forests, or their blingy cousins in Hollywood, New York, and Washington DC who delight in tricking the mass media, film industry and corrupt politicians into constantly making greedy, immoral, hypocritical fools of themselves, Iron Pixies (genus Fatum Ferrum), do not fear iron or iron alloys. Indeed, besides pilfering and concealing tools that contain iron, they love nothing more than to use their corrosive powers to return this metal to its natural state through the thermodynamic chemical process known as “rubeum, et conversus abibo” (turn red and go away).
These piratical pixies become especially joyful if the owner of the snatched tool is unable to find it after much frantic searching, and is eventually forced to buy a replacement. Only when they see the replacement tool will the pernicious pixies permit the owner to locate the pilfered tool, usually rusty and chipped.
We’ll come back to the supernatural aspects of woodworking tools, but first let’s examine some more mundane details about sharpening blades, and a few things that typically go wrong with them.
The Ideal Bevel Angle
There is such a thing as an “ideal bevel angle” for each blade in each cutting situation, one that cuts the wood quickly, cleanly, with minimum force expenditure and that keeps the blade effectively sharp for the maximum amount of cutting possible, but determining this angle is not an easy calculation since it is difficult and expensive to actually observe what is happening at the cutting edge from a shaving’s-eye-view.
For example, a steep 60° bevel angle on a chisel will support the cutting edge thoroughly and will be durable, but it will pound the wood more than cut it wasting time and energy and damaging the wood unnecessarily. On the other hand, a 15° angle will cut well, but is likely to chip and dull quickly. A balance is necessary.
This balance will depend on many factors including hardness and abrasiveness of the wood you are cutting at any time (e.g. Sugar Pine versus Ipe), the quality and nature of your chisel blade, the type of cut you are making (low-pressure surface paring versus high-pressure deep mortises), and the care you take to protect the cutting edge. Yes, technique matters.
Determining the ideal bevel angle is ultimately a trial and error process the diligent craftsman will unconsciously perform until it is second nature, but the following are some general guidelines to get you started.
Most Japanese woodworking tools, including plane blades and striking chisels (oirenomi, atsunomi, tatakinomi, mukomachinomi) perform well in most construction and furniture woods with the standard 27.5°~30° bevel angle. This is a good compromise, acute enough to cut most wood efficiently without too much friction, while still providing adequate support to the thin cutting edge to avoid chipping.
But like any rule, there are exceptions. For example, 35° is often a superior bevel angle for chisels when quickly cutting mortises in harder woods or planes shaving tropical hardwoods.
When cutting very soft woods, such as Paulownia, similar to balsa wood, a 22~24° bevel angle may work best.
Paring chisels (tsukinomi), when used properly, are subject to less violent forces than striking chisels, and can handle a 24° bevel angle. But for most woods, a professional-grade Japanese plane or chisel blade will likely experience chipping if the angle is much less.
There are many variables and potential solutions one might consider, but as a general rule, I recommend starting your experiment with a 27.5~30° bevel angle for plane and chisel blades.
If you find that your blade chips or dulls quicker than you think it should, increase the angle gradually until it calms down. This can result in a double-bevel blade, one difficult to sharpen freehand. In this case, I fully support using a honing jig, at least until you achieve a flat bevel wide enough and stable enough to sharpen freehand. But don’t handicap yourself by relying solely on honing jigs because they can become like training wheels on a bicycle: slow and childish.
Mercurial Bevel Migration
There is a strange, almost supernatural phenomenon many woodworkers experience, the first evidence of which is a plane or chisel blade that previously held a sharp edge a long time suddenly and unexplainably beginning to dull or roll or chip sooner than before. Even professionals with many years of experience occasionally see their tools exhibit this nasty behavior.
Some craftsmen faced with this dilemma begin to question their sanity. They may ask themselves: “Has heaven turned its face against me? How do I rid myself of this curse? Do I need to see a shrink?” Other craftsmen, more aware of the dangers of pernicious pixies, draw strange hex symbols on their walls or inlay brass circles and pentagrams into their floors to exorcise them from their workshop. Indeed, this practice has a long history in Europe and America.
Unfortunately, more than one blacksmith has been falsely accused of poor workmanship when the fault actually lay with the tool’s owner unwittingly allowing Iron Pixies to run amok. If this happens to your tools, please use the methods described below to purge any pestilent pixies in the area.
You would be wise to consider all possible causes of Mercurial Bevel Migration (MBM), including those unrelated to any infernal fiends that may or may not be skulking in your lumber stacks.
But if not pesky pixies, what else could cause this maniacal metallurgical malfeasance? Never fear, Gentle Reader, there is another possible explanation, one that can be resolved without paying for years of expensive psychotherapy and mind-altering drugs, or placing small bowls of blood and milk around your workshop, or enduring the pain of tattoo needles, or paying for stinky ceremonies involving burning sage and spirit drums.
The more likely cause is simply that it’s human nature when sharpening chisels and Japanese blades with their laminated, top-heavy construction to apply more pressure to the bevel’s rearward half (farthest from the cutting edge) abrading the softer jigane body more than the harder hagane cutting layer. Eventually, as the soft jigane wears away, the bevel angle will decrease to the point where the cutting edge will lose support and become fragile.
Once you are aware of this tendency and take preventative measures (and assuming you don’t have an iron pixie infestation), all should be well.
Next let’s examine some measures to get rid of both this bad habit and trixy pixies.
Pixie Predation Prevention & Pacification
If you suspect the presence of iron pixies, you should perform a Pixie Detection test. A reliable method is described in the next section below.
In any case, to avoid pixie infestation, you should create a workshop environment unfriendly to pixies. The following is an partial list of measures I have found to be effective.
Cleanliness: Clean bench surfaces and sweep the floors daily. Periodically vacuum and wet-mop workshop floors twice a year during the winter and summer solstices (approximately June 21 and December 21);
Add more lighting: Iron Pixies fear light because it reveals them to their enemies;
Keep a pair of boots near the door into the workshop: Pixies are deathly afraid of boots, especially when they contain the feet of sharp-eyed human children, but just the sight of boots will prevent them from entering a space;
Keep brass benchdogs in your workshop. Expert fairyologists insist, and I agree, that having a brass bench dog (remember, Iron Pixies do not fear iron or steel or the IRS) or two close by will banish Iron Pixies to the workshop’s dark recesses and keep their nasty claws away from tools. The deterrent effect of bench cats is unclear, but if you decide to rely on one, be sure it bothers to stay awake;
Welcome spiders: Although this may seem to contradict No. 1 above, Iron Pixies fear spiders, especially daddy longlegs, who tangle them in their webs.
Make regular offerings to the gods of handsaws. More on this subject in future posts.
A more mundane but sure way to prevent MBM is to make or buy a bevel angle gauge and regularly use it to check your bevels during sharpening. Aluminum, stainless steel or even plastic gauges will work of course, but brass or bronze are more effectual at purging perfidious predatory pixies because copper is toxic and zinc causes pixies indigestion. Be sure to store it close to your valuable steel tools to help repel the maniacal monsters.
Here’s the important thing: once you have this tool on hand, use it to check each blade before, during and after sharpening to ensure you are maintaining the correct bevel angle instead of allowing it to decrease incrementally over repeated sharpening sessions. Make this a firm habit. More on this important subject in future posts.
Remember to measure the bevel angle at the blade’s far right or left edges because the hollow-ground ura of Japanese blades makes it difficult to correctly measure the angle if you check it elsewhere.
Pixie Detection Methods
Iron Pixies are secretive creatures most people never see, but if you suspect you have an infestation, a detection test is called for.
While there are many proven methods to test for pixie infestation, the least expensive non-toxic iron pixie detection test is to sharpen a plane blade, and while doing so, attempt to “stick it” on the stone as in the photo below. This phenomenon is evidence the stone and the blade are in such perfect contact that the suction between the blade, water and mud on the stone’s surface strong is enough to support the weight of the blade.
If you are unable to accomplish this marvelous feat even after many attempts, you can be assured of the presence of peevish pixies nearby. In that case, use the preventative measures listed in the section above. You should also flatten your sharpening stones (especially the rough and medium grit stones) and make sure your blade’s bevel is perfectly flat. Bulging bevels are the pernicious pixie’s playground. (Aha! Iambic pentameter!)
Fair warning: If you stubbornly persist in your efforts to stick a plane blade before purging the area of pixies, they may go berserk to prevent this sublime event from occurring. If that happens, Katy bar the door!
In the next stage of our adventure, we will examine some of the health ailments blades commonly suffer. High cholesterol in chisels? Planes with pneumonia? Or just toolish hypochondria? Stay tuned to find out more.
Please share your insights and comments with everyone in the comments section below. If you have questions or would like to learn more about our tools, please use the questions form located directly below.
Our customers outside of Japan frequently need some information to help them select the best wood for their chisel handles. In this post I’ll describe the woods available and the advantages and disadvantages of each to help you make an informed decision.
The chisels we sell all have wooden handles in several varieties of wood, the two most common being Japanese White Oak and Japanese Red Oak. We also can provide handles for some chisels in Gumi (Silverberry wood), Ebony, and Rosewood. Let’s look at White Oak first.
Japanese White Oak
Japanese White Oak (JWO) is very similar to American White Oak in that it is closed grain, dense, and has medullary rays. The color is a little whiter than the American or European varieties, and in fact, it’s a little denser and stronger than either. It holds up well to being struck with steel hammers.
JWO is not a slick wood when dry and does not become slippery when wet, important characteristics in a tool handle where staying attached to the blade and staying secure in a sweaty hand while being pounded on are part of the job.
Like White Oak everywhere, it contains tannic acid. In fact, bark and chips from this wood have been used since before written history to tan leather because this chemical converts animal skins that would otherwise rot into durable leather. Tannin, which is the base word of both tanning and tannic acid, comes from the medieval Latin word tannāre, a derivative of tannum (oak bark), from which the tannic acid compound is derived.
Tannic acid can react with some people’s sweat causing the wood to turn a dirty grey color. This tendency is not strong among the Japanese people, but it is among many caucasians, including me.
This discoloration in no way weakens or harms the wood, it just makes it look dirty.
JWO generally has a bland, indistinct grain with few flecks, not a problem for a tool handle or plane block, but less than ideal for furniture.
Japanese Red Oak
Japanese Red Oak (JRO) is as different from American Red Oak as the “the moon and a mud turtle,” as they say over here. It is a much more useful wood.
Similar to JWO, Japanese Red Oak is closed grain and also has medullary rays. It contains much less tannic acid, and ranges in color from a dark red (difficult to obtain nowadays) to a pinkish red.
JRO has been prized in Japan for tool and weapon handles since forever. Indeed, JRO is the preferred wood for the bokken wooden swords used in the martial arts. The better grades are denser than White Oak with a more interesting grain. Unfortunately, this grade of Red Oak has become difficult to obtain.
As with Japanese White Oak, Red Oak is not a slick wood when dry and does not become slippery when wet.
There are unscrupulous people that dye less colorful pieces of Red Oak a dark red color to jack up the price. We don’t deal with such slimy people and our JRO handles are all authentic. Caveat emptor, baby.
JRO has the advantage of discoloring less than JWO over time and tends to look cleaner longer. It makes a more attractive handle.
The downside to the JRO generally available nowadays is that it is a little less dense than White Oak. I consider Japanese Red Oak to be the perfect wood for paring chisels, and Japanese White Oak the perfect wood for atsunomi chisels. Either wood works fine for the smaller oiirenomi bench chisels.
Gumi (Elaeagnus multiflora or cherry silverberry) is more a hedgewood or bush than tree. It has historically been cultivated primarily for the fruit it bears. It is stronger than Japanese White Oak, but lighter in weight. It has a distinctive yellow color that some people find attractive. I don’t get the attraction, but must admit it has a striking appearance.
Gumi makes a fine, durable handle. It is a more expensive material. My handlemaker has shorter pieces suitable for oiirenomi handles in-stock, but nothing longer.
Gumi handles are custom order.
Ebony and Rosewood
Ebony and Rosewood make elegant, durable, well-balanced handles for paring chisels, which are never struck with hammers and therefore unlikely to crack. But material costs are quite high. They are also custom order items that take some time to fabricate.
Oirenomi and atsunomi and other types of tatakinomi with ebony or rosewood handles look great. And in the case of amateurs that buy such chisels (from other sources) just to collect and/or admire, I have nothing to say. But we sell professional-grade tools to be used on real-world jobsites and in workshops by serious craftsmen for serious cutting, not to become safe queens. Using ebony and rosewood handled oirenomi or other varieties of tatakinomi to do real work is like wearing Jimmy Choo stilletto heels to a construction site.
Yes, Jimbo makes elegant shoes. And if your ensemble is well thought-out, a pair of his heels will make your legs look mahvelous dahling, simply mahvelous. Sadly, they will neither last long nor get the job done. Other workers will mock you behind your back. And embarrassing stuff will happen at the worst possible time.
For warranty reasons, we do not sell tatakinomi of any kind with handles of ebony or rosewood. They are too easily and irreparably cracked/damaged if struck with a steel hammer. Professionals will not purchase, and we will not sell, such silly tools.
While it has not been a problem so far, importation of some exotic hardwoods such as Brazilian rosewood into the United States can be a problem, according to the guitar makers I know and information on the infallible internet (ツ). If you order handles made from these woods, please be aware that you become the responsible importer once such materials cross into the jurisdiction of your local Customs Office. They may confiscate your tools or levy fines. The risk is all yours. That said, it has not been a problem so far.
Not encouraging, I know, but customs services worldwide are in the business of making literally tons of money every hour by taxing the entire world using their absolute authority within their bailiwick, and lots of guns. The most profitable income source for governments, as you know, is not taxes but making and circulating money (literally manufacturing money), followed by customs fees. Such it has always been; such it will always be.
On the other hand, we have experienced difficulties and customs duties in only two countries, namely Spain, which is notorious for once charging confiscatory import duties on gunpowder and cannonballs brought into Spain by Great Britain to free that country from Napolean’s armies during the French occupation.
Australia was brutally difficult on one occasion, but that incident may have been driven more by dazzling government incompetence rather than enforcement of the country’s importation laws.
For standard oirenomi and other tatakinomi intended to be struck with a steel hammer, either White Oak or Red Oak are entirely adequate and cost-effective. White Oak is a little stronger, but its appearance does not improve with use or age. Red Oak is not quite as dense and strong, but it is sufficient for these chisels and looks better over time.
For wider Atsunomi and Mukomachinomi (mortise chisels) which will see heavy use, White Oak is the best choice due to its higher density and superior strength.
If cost and delivery time is not a concern, you like the yellow color and want to be different, then gumi is an excellent choice for oiirenomi. It’s the same as the difference between brown leather work boots and tan-colored Timberland boots.
For usunomi and other paring chisels not intended to be struck with a steel hammer, Red Oak is the best choice, IMO, but White Oak will perform just as well. Gumi is not an option. Ebony and Rosewood look beautiful and feel nice (if you don’t have allergies to Rosewood), but are expensive and require lead time.
In the first post in this series, we examined the two main categories of Japanese chisels: the tatakinomi designed to be struck with hammer, and the tsukinomi used to pare wood without using a hammer. Beginning with this post we will shift our focus to several varieties of tsukinomi.
If you need to cut precise joints in wood, then you need both striking and paring chisels.
The most popular variety of tsukinomi is the mentori usunomi (面取り薄鑿）which translates to “beveled thin chisel.” The name is appropriate as the blade is long and thin and the neck gently tapered.
Just as with oiirenomi, the blades of tsukinomi can be made with different profiles, such as the rectangular cross-section of the kakuuchi, or the more triangular cross-section of the shinogi.
The usunomi has the more streamlined cross-section of the mentori oiirenomi with two bevels ground into the right and left sides of the blade’s face, flowing over the shoulders and feathering into the neck.
An atsunomi or oiirenomi can pare joints, of course, but the steel crown and mushroomed wood fibers on the handle’s end make them uncomfortable for such jobs. More importantly, the blades and handles of these chisels are often too short to provide adequate angular control. In short, the usunomi is more comfortable to use, and pares wood more powerfully and more precisely.
Western paring chisels by comparison are even thinner and have longer blades than Japanese paring chisels. There can be no denying they do a fine job. Japanese paring chisels like the usunomi have a few potential advantages worth considering, however.
The most significant advantage is that the steel cutting edges of Japanese paring chisels are much harder. The paring chisels my blacksmiths forge are around 65~66 Rc , whereas Western paring chisels are usually around 55 Rc. A Western style paring chisel with its thin blade of uniform steel hardened to 65 Rc would easily snap in half if stressed. This extra-hard steel makes possible an edge that stays sharper longer, with the result that, given the same number of sharpening opportunities and time in a given workday, a professional-grade usunomi will help you do more hours of high-quality work than a softer blade. For craftsmen that use their tools to feed their families this higher-level of performance is not something to be sniffed at.
The second advantage of the Japanese paring chisel is their hollow-ground ura which makes it easier to maintain a flat bearing surface. If you haven’t used Japanese chisels, this claim may sound unlikely. But please recall that there are narrow lands surrounding the ura, all in the same plane, that create a flat bearing surface to guide the chisel.
This tool is well-suited to reaching into narrow mortises and other wood joints to clean and pare surfaces roughed out by axe, adze, saw and tatakinomi to precise tolerances.
It excels at trimming mortise side walls and end walls. And shaving tenon cheeks and shoulders to precise dimensions without causing spelching or cutting too deeply as shoulder planes are wont to do is a piece of cake.
In addition, the longer blade and flat face of the usunomi make it ideal for paring angles, such a 45° mitres, in combination with wooden guide blocks or jigs.
The usunomi may be struck with the heel of the hand, but never with a hammer or mallet. The slender neck, thin blade, and unreinforced handle will simply not accept such abuse gracefully.
Chisels intended to be struck with a hammer typically perform best with a cutting edge bevel of 27~30°. Any shallower and the hard steel at the cutting edge may chip instantly dulling the tool. However, the cutting edges of usunomi along with other tsukinomi are not normally subjected to the high stresses chisels motivated with hammers must endure, so the cutting efficiency can be increased by lowering the angle to 24° or so without creating problems, depending of course, on the wood you need to pare and the type of paring you intend. For instance, paring end grain may require a steeper angle than long grain.
If you have used long-bladed Western chisels hard for a few years, you will have no doubt experienced your chisel’s flat becoming somewhat rounded over many sharpenings. This occurs because, for various reasons, the center portion of the blade’s flat is abraded at a slower rate when being sharpened than the blade’s perimeter, resulting in distortion regardless of whether you keep your stones perfectly flat or not.
Obviously, a chisel with a flat that is banana-shaped lengthwise and crosswise is not ideal for paring flat surfaces, but there is a bigger problem. Namely, it is simply more difficult and time-consuming to create a sharp edge on a blade with a curved flat than one with a true flat. A flat like this begs for amateurish tricks using rulers, etc.. of the sort professionals would be embarrassed to use. A friend once scathingly described these techniques as “training wheels.” Oh my.
The ura on the Japanese chisel is specifically designed to deal with this shortcoming, and it does a great job of it.
The 30mm usunomi in the photo above has an ura with three hollow-ground areas instead of one. This detail is called a ” mitsuura” ミツ浦 meaning ”triple ura.” It has the advantage of providing a larger bearing surface than the standard ura does, one that is helpful when using wooden jigs for paring to precise angles, for instance. It also helps the ura index better when paring large surfaces, especially with chisel blades wider than 24mm.
Some people prefer chisels with the mitsuura detail for their appearance. I admit mitsuura look sexy, but I am not a fan of using this detail unless it is truly necessary because of the downsides I will not deal with in this already overlong post.
If I can liken the atsunomi to a shire horse, then the usunomi is a falcon. Both are beautiful powerful animals, but just as one wouldn’t use a draught horse to chase down a rabbit, or a peregrin to pull a plow, neither oiirenomi nor atsunomi are as effective as the usunomi for paring and cleaning joints.
The usunomi is one of those tools that is a pleasure to use.
Among woodworking tools, the usunomi is special: as it becomes part of your hand, you will discover that neither the blade nor your hand but your mind is shaping the wood.
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Japanese mortise chisels are called “Mukomachi Nomi” 向待鑿. I am unsure of the origin of the name, but the Chinese characters can be read as meaning “wait over there.” A curious name, it may refer to the shape of the transition from blade to neck, called a “machi” which is unique in Japanese chisels. I will simply call them “mortise chisels.”
Mortise chisels are single-purpose tools for cutting rectangular holes in wood for mortise and tenon joints, the oldest recorded wood joint known.
Unlike other Japanese chisels, and even Western mortise chisels, the sides of the Japanese mortise chisel are shaped square to the “flat” instead of being angled slightly less than 90 degrees. The surfaces of the sides are of course straight along their length, but are either flat or slightly hollow across their width.
Other varieties of chisels have sides angled inwards to prevent the chisel from binding in the cut. This is less than ideal, however, when cutting small mortises because it allows the chisel to twist inside the mortise scoring the sides and reducing precision. The Japanese philosophy is that the blade’s sides should shave and clean the mortise at the same time it is cutting it so the sides don’t require additional cleanup with a paring chisel. Its a matter of precision and efficiency.
The straight flat sides of the mortise chisel have a relatively larger surface area that can create a lot of friction in the cut making extraction difficult in some cases, so the standard maximum width is 15mm.
Many advocate using double bevel cutting edges for Western mortise chisels. I have no problem with double bevels for atsunomi used to cut wide, deep mortises because the double bevel tends to kick more waste out of the mortise hole than a single flat bevel, although double bevels are more trouble to sharpen. But in the case of the standard Japanese mortise chisel, I recommend using a simple flat bevel for two reasons:
The first reason is that, since sharpness is critical for precise work, and a flat bevel is quicker and easier to sharpen, a flat bevel is more precise.
The second reason is that a flat bevel tends to stabilize the chisel in the cut more than a double bevel blade can, keeping it from twisting out of alignment and gouging the sides.
The mortise chisel is a specialist chisel for joinery, cabinetmaking and furniture work. It is not generally used by carpenters. Craftsmen that routinely use mortise chisels work to much tighter tolerances than most woodworkers, so a professional-grade mortise chisel must be forged and shaped to tighter tolerances than other chisels.
I only have one blacksmith with the skills and attention to detail required to make mortise chisels to my specifications. He thinks I’m too picky. I think he’s too stubborn. We’re like an old married couple（ツ).
If you need to cut lots of precise mortise holes quickly, then this tool will definitely improve your results and increase your satisfaction. It may not be the most handsome chisel in your toolchest, but you will come to rely on it more than any other for quality joinery work.
Standard widths for mortise chisels are 3mm, 4.5mm, 6mm, 7.5mm, 9mm, 12mm, and 15mm, but Sukezane won’t make 15mm mortise chisels for me anymore, dagnabit.
More than any other, mortise chisels are subtle, intelligent beasties, or at least they can be. I will talk more about what to look for in a good mortise chisel, as well as how to realize their Einstein-like focus to help you do better work, in future posts.
“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.