The Care and Feeding of the Wild Mortise Chisel – Part 1

Sukezane brand 9mm mortise chisel (mukomachinomi) side view

It is well with me only when I have a chisel in my hand

Michelangelo 1475-1564

This is the first in a five-part series about the Mortise Chisel, especially the Japanese version.

Also called the “Joiner’s Chisel” in Japan, this is a specialized chisel used by specialist craftsmen to cut precise, smallish joints when making furniture, cabinetry and joinery. Carpenters don’t use it, and few have in that august trade have even seen one.

In this post your humble servant will introduce a tiny bit of the terribly long history of the mortise and tenon joint, and give a description of this specialized chisel.

In future posts we will look at how to evaluate, adjust and even how to use the Mortise Chisel in general and the Japanese Mortise Chisel in particular. We will also touch on bevel angles and blade hardness problems.

We will discuss what to look for in a good mortise chisel and how to examine it with an eye to increasing its performance. This is something most users of chisels never consider, but it can make a big difference in the case of mortise chisels. Indeed, I daresay most Gentle Readers will mutter the equivalent of “Bless us and splash us” when they read it.

Of course we will also discuss how to effectively correct irregularities in our mortise chisel that negatively impact performance, irregularities most people never notice.

After our Mortise Chisel is properly fettled (they almost always have some problems) we will take our racing chisel out for a few laps, but prior to that we will consider how to effectively use this specialized tool. Too few receive proper training nowadays in chisel work, but here are C&S Tools we feel it our duty to help our Beloved Customers improve their skills.

We will conclude this series by taking the “Old Master’s Test,” just to make sure both our Mortise Chisel and our skills are improving.

While focused on the Japanese Mortise Chisel, the principles and improvements discussed in this series of articles are applicable to any chisel used to cut mortises.

While all Gentle Readers with eyes to see, ears to hear, and hands that love wood are welcome to share this hard-earned knowledge, it is intended primarily for our Beloved Customers, especially those who use chisels professionally to keep body and soul in close proximity.

Some Background

Your humble servant drafted this series of posts years ago, and has shared bits of it with Beloved Customers from time to time when requested, but the information has not always been well-received for a number of reasons.

There is an old Japanese saying, one which probably originated in China, written 「馬の耳に念仏」and pronounced “Uma no mimi ni nenbutsu,” which translates to “Prayers in a horse’s ear.” Why are Buddhist prayers relevant you ask? Good question. You see, some of the principles I will present in this series directly contradict doctrine taught by some of the Holy Woodworking Gurus in the West. Like vespers to a beast of burden, wisdom is wasted on the willfully, woefully ignorant (wow, that almost sounds like iambic pentameter!).

But our Beloved Customers are neither horses nor asses nor politicians but shockingly intelligent human beings to whom your humble servant is convinced the time has come to expound the gospel of the Mortise Chisel as it was taught to me by Masters who have since abandoned this impure world for more ethereal realms.

This series of posts is equivalent to a graduate school course in chisels, something like “Mortise Chisels 701.” And just like a course in advanced differential equations, most Gentle Readers will never need it. But never let it be said that your humble servant didn’t do his best to improve both the skills and the tools of our Beloved Customers.

Some History of the Mortise & Tenon Joint

Mortise chisels are used for cutting rectangular holes in wood usually intended to accept tenons to form a structural connection called the “mortise and tenon joint” between pieces of wood.

No one knows how long humans have been using the mortise and tenon joint, but it has certainly been longer than nails, and many thousands of years longer than screws, although modern humans with their lithium battery-powered, made in China, landfill-bound, multicolored plastic and rubber screwdrivers may find it difficult to imagine. So let’s begin the journey by briefly examining just two well-documented extant physical examples that may provide motivation for using this enduring joint.

The oldest known wooden structure is a neolithic well liner discovered near Leipzig Germany, constructed from oak timbers shaped by stone adze and joined at the corners with half-lap joints and pinned tusk-tenons at through mortises. Tests indicate the trees the timbers were split from were felled between the years 5206 and 5098 BC, making the assembly at least 7200 years old.

Next, let’s look at a less soggy but more recent, complicated and elegant example.

The oldest existing wooden building in the world is a Buddhist Temple named Horyuji located in Nara Japan. Originally constructed around 600 A.D. and rebuilt around 700 A.D. after a fire, this huge 1300 year-old temple and pagoda complex was reconstructed using hundreds of thousands of hand-cut mortise and tenon joints, testifying to the longevity of wooden structural systems and the value of this universal connection technique.

Horyuji  is far more than just a temple to Buddhism, it is a temple to woodworking. If you haven’t yet visited it, you’re truly missing something. 

I mention these two examples to illustrate the universality, strength, and durability of the mortise and tenon joint. Anyone serious about woodworking must master this most ancient and essential connection.

The mortise chisel is the best handtool for the job of cutting mortises less than 15mm in width. For wider mortises, well-fettled oiirenomi or atsunomi are more efficient.

Japanese Mortise Chisels

12mm mortise chisel (mukomachinomi) Face View
12mm mortise chisel (mukomachinomi) Side View
12mm mortise chisel (mukomachinomi). Please notice the rectangular cross-section precise right angles, and straight, clean sides. This is the most precise of the Japanese chisels.

In the Japanese language mortise chisels are called “mukomachi nomi” (向待鑿), with “nomi” meaning “chisel.” Don’t ask me the origin of the rest of the word because I don’t have a clue, and have heard few plausible explanations. There is another post linked to here that contains more information about this chisel.

I will use the term mortise chisel in this article to refer to mukomachi nomi.

For our Gentle Readers interested in the Japanese language, there are several combinations of Chinese characters used to write mukomachi, none of which make much sense or seem related in any way to either tools or woodworking. The most common characters used are “向待” with the first character meaning “there” or “direction,” and the second character meaning “wait.” Combined, they seem to mean “Waiting over there,” or something like that.

I assume the name was originally phonetic and somebody decided to use these kanji because their pronunciation matched the phonetic name. This sort of linguistic contortion is seen frequently in Japan, and has been a source of confusion for all and sundry for many centuries. I blame it on elitist Buddhist priests going back and forth between Japan and China over the centuries, but it is typical of the Japanese people in general and priests in particular to take a perverse pleasure in intentionally making and using terms others can’t figure out.

This confusing practice is not unique to bald priests. When I was an engineering student, I recall the professors insisting we never attempt to simplify or too clearly explain the technical jargon of the trade to non-professionals because it was essential to job security for them to never quite understand it.

If you are familiar with Japanese architecture, you have seen the wooden lattice work that defines it in doors, windows, dividers, shoji, fusuma, koshido, glass doors, ceilings, and even fences, all items made by “tategushi” or “joiners” in Japan. Each piece of any lattice needs two tenons and two matching mortises to stay in-place, so a single piece of traditional Japanese joinery may have literally hundreds of small, very precise mortises, indeed thousands in the more complicated pieces. The Japanese mortise chisel was developed specifically at the request of joiners for this type of work. Therefore, it is also known as the “Tategu Nomi” which translates to “joinery chisel.” Few carpenters use this chisel.

Nora Brand 6mm Mortise Chisel (Mukomachinomi) Side View. Although it appears to be a simple, unsophisticated tool, nothing could be further from the truth. Based on the Kiyotada pattern, this is an especially beautiful example to those with eyes to see.
Nora Brand 6mm Mortise Chisel (Mukomachinomi) Ura View
Nora Brand 6mm Mortise Chisel (Mukomachinomi) Shoulder View. Exceptional shaping and filework .

Japanese mortise chisels are similar to other Japanese chisels in having a laminated steel structure with a hollow-ground ura (flat), an integral tang, wooden handle, and steel ferrule and hoop. Unlike most other chisels it has a rectangular cross-section with sides usually oriented 90˚square to the hollow-ground ura, and either flat or just slightly hollow-ground to better keep the blade aligned in the cut and to dimension and smooth the mortise’s walls.

Western mortise chisels do not typically share this detail, although unusually intelligent and observant Western woodworkers of course modify their chisels to gain similar benefits.

If speed and precision are important to you, then the sides of the chisel being oriented at 90° to the ura absolutely provide a serious advantage when cutting most mortises because the sides, and especially the two sharpish corners where these three planes meet, will effectively shave and precisely dimension the mortise’s side walls as the mortise is being cut without the need to pare them later.

Unlike most mortise joints cut with oiirenomi or atsunomi, so long as the mortise is the same width as the mortise chisel, and the user has the ability to maintain the chisel at the right angle while striking it with a hammer, the width of mortises cut with this chisel are usually quite precise and seldom if ever need be cleaned with a paring chisel. This functionality means that you can cut mortises, and especially small ones, both precisely and quickly with great confidence. It’s not called the “joiner’s chisel” for nothing.

The mukomachi chisel does not work as well in wider widths because of the increased friction between the chisel’s sides and the mortise’s walls. For joints wider than 15mm, please use a trued oiirenomi or atsunomi. And don’t forget to use your oilpot.

In the next class in our graduate course on the care and feeding of the wild mortise chisel, we will examine the various details to look for in an effective mukomachi nomi. Most of these details are applicable in the case of other chisels such as oiirenomi and atsunomi too, indeed any chisel intended to be used to cut mortises including Western mortise chisels.

But wait a minute! Before ya’ll run out of the classroom like a caravan of crazy stoats chasing a pixie, please pick up your homework assignments from the table by the exit doors. And please, don’t leave your empties behind on the floor. Paper coffee cups are one thing, but diascarded aluminum beer cans attract out-of-work divorce lawyers and other such desperate vermin.

See you next time.

YMHOS

Your most humble and obedient servant’s set of well-used mortise chisels. The 8 pieces on the right are by Kiyotada (1.5mm~15mm). The two 2 newer chisels on the far left are by Nora. Over the years I have used these tools both professionally and as a hobbyist more than any other of my chisels, as you can perhaps tell from the differing blade and handle lengths which have become shorter with use. A stoic tool, they gossip among themselves less than most other chisels. They are good friends and reliable workmates that worked hard for many years to pay rent, tuition and food for the wife and babies.

If you have questions or would like to learn more about our tools, please click the see the “Pricelist” link here or at the top of the page and use the “Contact Us” 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, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may Mama Shishi bite my head off.

YMHOS

Other Articles in “The Care and Feeding of the Wild Mortise Chisel” Series

The Care and Feeding of the Wild Mortise Chisel – Part 1

4 thoughts on “The Care and Feeding of the Wild Mortise Chisel – Part 1

  1. I am very excited for this series! And to find some smaller mortise chisel. The question as to angle is interesting to my beginner mind. Is lower better for end grain? Or is high for holding edge? Don’t tell me, yet—I will let the series unfold.

    Smaller mortise chisels are not that common, these days, it seems. It also feels like for what most Americans do most commonly with Japanese tools (small joinery in small to medium casework) it should be a more commonly utilized tool here.

    Thank you for writing this. And validating my appreciation for this tool, which I felt strange about liking. I couldn’t believe how fast and true my mortise ends were the first time I tried one.

    B

    On Sat, Mar 6, 2021 at 1:13 AM Covington & Sons Tools wrote:

    > covingtonandsons posted: ” Sukezane brand 9mm mortise chisel > (mukomachinomi) side view It is well with me only when I have a chisel in > my hand Michelangelo 1475-1564 This is the first in a five-part series > about the Mortise Chisel, especially the Japanese version. Als” >

    Like

    1. B: Sorry my response is slow. Thrilled you like the series. In answer to your questions, the perfect bevel angle varies with wood and technique. Paulownia needs a shallow angle and a very sharp blade, so 20˚? Ebony needs a higher angle, so maybe 40˚? If a guy is in a hurry and uses the 20˚ chisel to lever out wood when making a kiridanusu, no damage done, but do the same thing when making an ebony mizudansu, or simply pound the chisel in too deep, and even 40˚ may not be enough to maintain a sharp edge for long. Make sense? Those who scorn craftsman-like advanced technique should stick with A2 pigstickers and enjoy some bacon.

      The thing about mortise chisels is that when they work well they are your best friend saving time, making the work easy and precise at all stages, and generally making the user feel extremely competent. But a skewampus mortise chisel is an enemy to good work and sanity. The difference? Shape and dimensions. Even a sketchy mortise chisel can do good work if the user trues it and uses it properly. Problem is, most people don’t realize why their mortise work is so difficult or why their mortise holes are so ragged. They blame their lack of skill, or the joint, or the wood when the problem is almost always a combination of their chisel being out of tolerance and themselves not thinking to do a cause and effect analysis of why their results suck big donkey donuts. I was taught the tricks of the trade by a professional joiner of some renown back in the mists of time. I am only sharing what I learned, and absolutely know works. It won’t help the lazy man or the slob, much less the willfully ignorant, but I can only do what I can do. Stan

      Like

  2. Here I am… Eager to make my first mortice. A sharp and square mortise chisel in my left hand, my right hand reaches for a hammer, yet only a head can be seen where once a hammer was. Those web page stealing pixies! Where is the article on choosing wood? Where is it?

    You Pixies! You thieves… You filthy little pixies! Where is it? Where is it? They stole it from us. My Precious handle, my preciousss..

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s