The Japanese Gennou & Handle Part 2 – Ergonomics

“We become what we behold. We shape our tools, and thereafter our tools shape us.” – 

Professor Marshall McLuhan
A Kosaburo hand-forged gennou head on a Black Persimmon handle

Marketing and mass-production have changed many things, but not how the human body works.

In this post we will examine some ergonomic factors of hammers you may find interesting, and ask some questions you may want to consider.

Ergonomic Factors

Making tools that fit the user’s body and way of working is an old idea. Here is an example.

Since the time I was a boy with a Daisy BB gun, I have enjoyed making beautiful rifle stocks using marbled walnut for my bolt-action guns and curly maple for flintlock longrifles. But a custom gunstock is not just a chunk of beautiful wood.

During my research into the art I learned how craftsmen have, for centuries, made custom shotgun and rifle stocks to fit each customer’s body. Indeed, unlike factory stocks, custom gunstocks are not straight, but are bent, twisted and offset in subtle ways to fit their user’s bodies to provide a steadier hold, quicker target acquisition, and reduced recoil. These techniques work.

Indeed, there’s a surprising number of calculations one must crunch, measurements that must be made of the rifle’s components, and details of the user’s body that must be determined in advance of designing a custom rifle stock. I’m talking about a rifle made using thousands of dollars of wood and precision-machined steel, designed to fit a particular person’s body, and intended for a particular type of shooting, not a K-Mart blue-light-special killer of unsuspecting tin cans.

Through trial and error and handwork I learned how employing these ergonomic principles could yield significant improvements in the performance of everything from reproduction flintlock longrifles to 1000 yard target bench guns, and even .45 caliber bolt-action elephant rifles. When I heard that a group of specialist Japanese carpenters had, over centuries of experimentation, developed tool handle designs that applied similar principles, the pieces clicked together in my mind like a Purdy double-gun’s breech.

A hammer is not a complicated piece of precision machinery like a modern benchrest target rifle, so we tend to think of the hammer as a stupid tool lacking finesse, but I disagree. Let us consider some of the challenges the lowly hammer is expected to meet that an ergonomic design can help it overcome.

The first challenge is air drag. The hammer is the most dynamic handtool a woodworker uses, moving relatively long distances at relatively high speeds. And during the swing the hammer pushes a lot of air aside creating drag and expending energy. It adds up. This is just one reason why big-faced mallets are inefficient compared to a steel hammer. There are those who will revel in their ignorance by disputing this fact, but to them I say: There is no medicinal cure for stupidity so learn some basic math. If you remember your freshman physics classes, you will recall that the formula for drag in a fluid (which includes air) is as follows:

F_{D}\,=\,{\tfrac {1}{2}}\,\rho \,v^{2}\,C_{D}\,A

where F D is the drag force, ρ is the density of the fluid, v is the speed of the object relative to the fluid, A is the cross sectional area, and C D is the drag coefficient, a dimensionless number.

The drag coefficient depends on the shape of the object and on the Reynolds number {\displaystyle Re={\frac {vD}{\nu }}},

You don’t need to input actual numbers into this formula to see that the two factors in this equation we can readily control are the area of the hammer (A) and its speed (v). The factor that we can manipulate to our benefit when designing our handle is the area (A), which includes not only the size of our hammer’s face but the width and length of its handle.

Second, when using our hammer we draw its head back beyond the range of our vision, and then, without looking, swing it with great force to precisely hit targets as small as a chisel handle or nail head, while avoiding hitting our own head, ear and hand. If the hammer’s head naughtily wiggles out of proper alignment during the swing, a headache or smashed finger may result, so we need a hammer head and handle combination that will be easy to keep in alignment during the swing without giving it a lot of thought.

The third challenge our hammer must overcome is the tendency of its striking face to impact the target with its center of mass misaligned with the centerline of the nail or chisel, or with the striking face canted forward or backward or to the side instead of square to the target’s centerline. Think about this next time you bend a nail or your chisel cuts in one direction when you wanted it to cut in the opposite direction.

A person proficient in using mass-produced hammers must train their eye and body to match the hammer they are using at the moment. Of course, this can be done, but it is inefficient. What I am proposing instead is to design our hammer handles so they match our individual bodies and the work we need it to perform instead of being forced to adjust our grip and swing to fit standard one-size-fits-nobody design parameters.

A lot of blowhards and marketing departments give lip-service to so-called ergonomics, but not here at C&S Tools, madame. Indeed, in future posts in this series we will discuss in great detail a number of ergonomic factors our Beloved Customers should include in their gennou design specific to their individual bodies and style of work, including the length of the hammer handle, twist and offset, grip location and shape, handle details to help the gennou index automatically in their hand without having to actually look it, and of course, the angle of the head.

We will both explain why and show you how to design, draft, and make a hammer handle suited to overcome these challenges while in your hand.

Questions

I am not fond of gaudy, decorated tools, but that does not mean my tools are plain as mud. As you may be able to tell from the photographs of one of my favorite gennou in this article, I enjoy subtle details that give them a unique attractive appearance, especially if those details improve their performance. My gennou are tools that please both my eyes and hands. I don’t know if they have shaped me, as Professor Mcluhan suggests, but they certainly give me more confidence and joy in my work than a run-of-the-mill rubber-handled hammer ever could.

For years I have encouraged people to ask themselves three questions on the subject of hammers. So I pose them to you now, Gentle Reader.

First, does your hammer and its handle fit your body and style of work, or is it a “one size fits nobody” product made by a conglomerate that knows everything about selling hammers but nothing about using them?

Second, is your hammer aesthetically pleasing to your eye and an extension of your hand, or is it like every other hammer that ever fell off the hardware store’s rack?

And finally, is your hammer likely to become an heirloom appreciated by your descendants, or will it end its days sad and lonely in a landfill?

If you answered nay to any of these questions, I promise you will find something of value in this series of posts.

In the next post in this series on designing and making gennou handles, we will examine some history and the ergonomic factors that resulted in the design that is the subject of this series.

YMHOS

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 profitably “misplace” your information.

Previous Posts in The Japanese Gennou & Handle Series

Part 1 – Introduction

Part 3 – What is a Gennou?

Part 4 – Varieties of Gennou

Part 5 – Kigoroshi

The Japanese Gennou & Handle Part 1 – Introduction

I do think a carpenter needs a good hammer to bang in the nail.

Oliver Reed

Introduction

This is the first in a series of posts about the Japanese gennou hammer (pronounced “gen-noh) in general and and how to design and make a unique one that perfectly fits your body and style of work.

The objective of these posts is to share with you, Gentle Reader, what I have learned over the years about gennou handles to help you design and make your own handle.

I will gladly share the entire series, including the drawings, as a single document with Beloved Customers upon request.

The True Craftsman Makes His Own Tools

A handful of generations ago quality high-carbon steel was difficult to make and expensive, so woodworkers worldwide, especially Japan, could not afford many tools, and the ones they did own or inherit were very important to them.

At least partly to reduce costs, it was standard practice back then for a woodworker (or his master) to commission the metal parts of his tools, such as the heads of his axe, hatchet, adze and hammer, and the blades of his chisels from the local blacksmith. In the United States or other British colonies a craftsman may have purchased chisel and plane blades imported from Sheffield, but he would not want to pay the high costs of shipping wooden components across oceans and over mountains when he could make them himself. After all, woodworking was his business, so a self-respecting craftsman would make all the wooden components of his tools, such as handles and plane bodies, himself as a matter of course. Needless to say, those old boys knew how to make handles.

But things have changed. You may not realize it, but we live in a time of extreme wealth where even the poorest live better than most humans did 100 years ago, partly due to widespread industrialization of all aspects of our societies making the necessities of life, and even what would have been called luxuries, available to everyone cheaply. This industrialization combined with cheap transportation has resulted in craftsmen purchasing pre-manufactured many things they would have made for themselves as a matter of course, including tool handles. I would wager that most woodworkers younger than 60 years old have never made an axe handle, hammer handle, or a plane body, and don’t even know how to.

Accustomed to the easy availability of standard tools, lacking an eye for performance and focused like a laser on lowest cost, most woodworkers nowadays get by with poor quality tools made by farmers in Chinese factories from poor quality scrap metal designed by kids using computers working in marketing departments that have never used a handtool professionally. Those tools may look great on the internet or wrapped in theft-proof plastic hanging on pegs in the big-box retailers, but how do they perform? And how long will they last? And what do they say about the men using them? Tools are terrible gossips, you know.

You cannot purchase a hammer handle like the one we will discuss in this series, and no one can make it for you. A hand-forged gennou head fitted with a handle made in accordance with the guidelines presented in this series will become a unique lifetime tool and the sure sign of a superior craftsman. More importantly, it will help you work more efficiently and give you greater confidence in your skills.

If you think this all sounds too good to be true, I challenge you to put it to the test. In fact, there will be a series of performance tests listed in the last post in this series that will allow you to generate hard proof of the truth of these claims for yourself. You will be impressed with the results.

While Japanese hammers are the primary focus of this series, you can apply the ergonomic principles and solutions I will describe to all varieties of hammer and axe handles.

Modern Tools: Marketing, Design & Manufacturing

I grew up using hammers designed for maximum sales in a competitive marketplace of amateurs, of the type I call “One Size Fits Nobody.” Back then they were made in the USA, but nowadays they are cheaply mass-produced in China. Prices are rock-bottom, and quality is focused solely on getting an attractive product out the door at the right price-point while fending off the hordes of snaggle-tooth slavering lawyers that specialize in product liability and personal injury lawsuits. To these corporations, you and I are beasts in a herd, of no import beyond the content of our wallets and our willingness to open them.

Like the cover of a manga comic book, mass-produced modern tools are carefully designed to immediately draw the eye and excite the senses of those passing by. Bright colors and futuristic shapes war with each other for attention on the pegboards of big-box retailers. Handles are made of plastic and rubber over steel or fiberglass, secured with globs of glue intended to hide malformed ulcerous eyes.

The designers of these blister-makers and nail-benders intend their products to age poorly so they will be discarded by purchasers after just a few years to ensure unending sales of new-and-improved replacements. Plastic and rubber are the materials of choice because they are cheap to fabricate, easy to make colorful, look exciting when new, and speedily surf the spiral wave into the depths of the toilet of planned obsolescence. 

The international playboy that Billy Crystal introduced the world to in “Nando’s Hideaway” might have been talking to one of these hammers when he said “This is from my heart which is deep inside my body: You look mahvelous, absolutely mahvelous dahling. Remember, it is better to look good than to feel good.” Perhaps these tools do look mahvelous hanging on those pegboards. But how good do they feel?

The tool conglomerate’s product development departments and marketing geniuses have taken the Latin Lover’s philosophy to heart. They know that tools that look good and turn to garbage quickly sell better and are more profitable than tools that merely feel good. I am sure ‘Nando would go “crazy nuts” if he observed modern hammers in their natural environment, but alas my friends (saludos, my darlings, you know who you are), Nando will not make the journey to a big-box home center to inspect their pegboard tools because he does not feel good.

Clever people these marketing strategists, stuffing their pockets with money and landfills with plastic and scrap metal by selling imitation tools to the herd. But as for me, I’ll have none of that churlish fraud, than you very much.

Would you buy a hammer like this? If so, please don’t call yourself a craftsman or operate heavy equipment.
Wow, a comprehensive torture kit. And just the right color too. Please don’t puke on your computer or smartphone.

Hammer Handle Morphology

The hammer is an extremely simple tool, literally as old as rocks. I suspect humans made the first multi-component tools by attaching wooden handles to stones to make hammers, axes and clubs. 

People have all but forgotten how to make a proper tool handle nowadays, but it wasn’t always that way.  Everyone made their own replacement handles only five generations ago, and their expectations were guided by sweat and blisters. They didn’t need product development departments in Shanghai to tell them what handle worked best.

Axes are an obvious example of how marketing has morphed handle design. Take a gander at an old tool catalog and notice how axe handles have become thicker and curvier in the last 120 years. Do these changes mean that for millennia humans didn’t know how to use axes or make proper handles for them? Do modern human joints and tendons endure the higher vibration and impact forces a thicker, heavier, stiffer handle transmits better than those of our forefathers? Has the nature of modern trees changed such that grain runout no longer weakens a handle made from their wood? No, these recent changes in handle design are not intended to make tools more functional, or more durable, but are rather intended to increase sales of cheaply mass-produced tools of apparently innovative design, but of mediocre quality and disposable utility. They simply look mahvelous, absolutely mahvelous dahling, especially as an illustration in a catalogue or hanging on a peg in a hardware store.

But please, don’t get me started on modern mass-market saw handles.

In the next post we will look at the history and types of gennou hammers. In the meantime, here is some music from Fernando.

YMHOS

PS: Here is an excellent article about the “Devolution of Axe Handles” that jives well with my research and experience, and the advice my grandfather gave me about making an axe handle 50+ years ago.

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 profitably “misplace” your information. I swear it on a stack of bibles.

Subsequent Posts in The Japanese Gennou & Handle Series

Part 2 – Ergonomics

Part 3 – What is a Gennou?

Part 4 – Varieties of Gennou

Part 5 – Kigoroshi