The Oiirenomi (pr0nounced Oh-ee-reh-no-me) is the most common variety of Japanese woodworking chisel, and the style best known both inside and outside Japan. There are several types of oiirenomi. In this post we will look at the most popular type of oirenomi called the ”mentori oirenomi” ( 面取り追入鑿) meaning ” beveled” oirenomi.
As mentioned in my previous post in this series, nomi means ” chisel, ” but the term ”oiire” 追入れ” is not so straightforward. It is composed of two Chinese characters: ”Oi” 追いmeaning ”to chase” or ” to follow,” and ”ire” 入れ meaning ” insert” or ”place in.” I am uncertain of the origin of this word, but some hints of the original meaning may perhaps be deduced from the characters.
As the name suggests, this chisel’s face is beveled at both sides making it lighter and better able to get into tight locations than the older-style kakuuchi oiirenomi, the forerunner of this chisel, which we will examine in a future post.
I think most people agree that the two bevels moving up the blade, curving around the shoulder, and feathering into the neck give this chisel a sculptural, elegant appearance. The bevels do sacrifice some stiffness and authority compared to the kakuuchi style, but clearly, these compromises are acceptable to most consumers.
A member of the tatakinomi family, it is designed to be struck with a steel hammer and has a hoop (called a “katsura” in Japanese which means “crown”) on the handle’s end to prevent splitting.
There are larger types of tatakinomi called atsunomi better suited than the oiirenomi to heavy cutting and wasting wood in applications such as timber frame joints, and most of those share the same mentori bevel detail, but oiirenomi are better suited to lighter tasks such as furniture work and interior installation work the same as Western bench or butt chisels.
Oiirenomi in general and mentori oiirenomi especially are light-weight, relatively inexpensive, and handy to use. All woodworkers in Japan own at least a few of these.
Materials and Manufacturing Techniques
Our oiirenomi are hand-forged by traditional self-employed blacksmiths with at least 40 years of experience working in their self-owned one-man smithies. They are stubborn gentlemen absolutely dedicated to quality.
These blacksmiths use only Hitachi’s Metal’s Yasuki Shirogami No.1 Steel (aka “White Steel”) for the cutting edge, a plain, exceptionally high-purity, high-quality, high-carbon steel that does not contain significant amounts of chrome, molybdenum, nickel, vanadium, or tungsten, chemicals which are added to nearly all commercial tool steels to make products easier to mass-produce by factory workers, instead of more expensive skilled blacksmiths, with fewer rejects. These alloys add considerably to the cost of the materials, while resulting in a finished product that will not become as sharp as Shirogami steel, will not hold a sharp edge as long, and will be more unpleasant and more time-consuming to sharpen. If you have the sharpening skills, then Shirogami No.1 is a steel you should experience.
The Shirogami high-carbon steel is actually a strip that our blacksmiths forge-laminate to a softer low-carbon steel body and neck. During heat treatment the high-carbon steel layer becomes very hard, but the low-carbon steel body and neck remain relatively soft. In use, this construction protects the hard steel from breaking, which is what would happen if the entire chisel was made of one piece of steel hardened the degree Japanese professional woodworkers demand. It also makes it easier to sharpen the hard cutting edge, a task that would be difficult if the blade was all the same hardness. Please see this this page, this page, and this page to learn more.
Our blacksmiths perform a minimum of 3 heats to each blade while using hammers and spring hammers to forge this special steel. This “hand-forging” process, combined with the special heat-treatment techniques they have perfected over many years, produces a “fine-grained” steel of the sort that has been coveted by professionals for tools and weapons since ancient times. The final hardness is between 65~66 on the Rockwell C hardness scale. Most Western Chisels are softer at 55~60 HRc. This extra hardness makes the blade stay relatively sharper longer, and the fine-grain crystalline structure of the steel ensures each blade will become sharper without sacrificing durability.
These are professional-grade tools made by craftsmen, not factories, and are intended to meet the severe performance expectations for Japan’s most uncompromising woodworkers, unlike the mediocre-quality but attractive-looking “consumer-grade” chisels peddled inside Japan to the amateur market, and outside Japan to the uninformed. How much bacon do you like with your sizzle?
Our oiirenomi are available individually, or in discounted 10 piece sets (3, 6, 9, 12, 15, 18, 24, 30, 36, 42mm) with Japanese Red Oak or White Oak handles. We have all varieties in-stock ready to deliver.
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