The Japanese Gennou & Handle Part 13 – The Drawing Part 2/6

This gennou’s handle has a pronounced curvature, a design detail that is neither artistic or whimsical but is based on sound engineering principles employed to achieve specific functional objectives.

In the previous post about designing a handle for your gennou hammer on paper we discussed the reasons for making a drawing and a few of the details. In this post we will begin by representing the head and its key lines in our drawing.

But first, a disclaimer. Some of our Gentle Readers will find the idea of making a drawing in preparation for making something as apparently simple as a handle made from a single stick of wood nonsense, even irritating. Indeed, I felt the same way once, but I was wrong. That is not, heaven forefend, to imply that our Gentle Readers could ever possibly be wrong in anything they undertake, or less than towering intellectual giants, only that the lowly gennou handle is not as simple as it appears.

You may recall your humble servant mentioned the two points listed below in a previous post. They remain valid principles that should guide your eye and hand when making a drawing. Or, if wood costs you nothing and your time is worth even less, feel free to ignore them.

The first point goes like this: “When making some things, past a certain point there is simply no room for either improvisation or trial & error without starting all over again.”

The second point is a little longer, but no less valid: “The principle of “less is more” absolutely applies, but achieving an elegant and functionally superior “Less” is neither accidental nor serendipitous, but can only be consistently realized through “More” thought, planning, and eyeball time, things difficult to do without a drawing.”

A Sample Drawing

The drawing below is an actual drawing your humble servant prepared for one of his gennou incorporating a 375gm (100monme) classical-style head by Kosaburo. Although it’s a simple drawing made entirely by hand, it includes all the critical details other than the species of wood and flow of the grain. Please notice that it consists of a top view, side view, end view (butt) and 2 sections, all combined in a one-sheet, compact drawing.

You will want to make a similar drawing incorporating all the lines shown but adapted to your gennou head, your body’s dimensions, and your preferences.

You can download this drawing in jpeg format by clicking the link below.

Draw the Key Lines for the Side-view

The gennou that resulted from the drawing above. This handle has a distinctive curve that is neither a result of warpage nor evidence of your humble servant’s advancing senility, but an intentional design feature we will discuss in the next post. I’m supposed to take these Gingko pills, but I forget why…

You can make your drawing on paper or wood, with wood being the more durable medium since ancient times because it does double duty as both parchment and drafting board, and can be erased entirely with a handplane. Moreover, the combined drawing and drafting board can be hung on a nail on the wall for future reference without fear of deterioration. But paper is easier to use.

Begin by making one horizontal parallel line across the sheet of paper. In the drawing above, this is the horizontal line touching the flat face of the hammer labeled “Striking Face.”

When orienting your head on the drawing, the flat striking face must face towards the bottom of the page. The head’s brand will be nearest the striking face and facing towards the right edge or butt of the handle.

Draw a vertical line, of course perpendicular to the Striking Face Line you just drew, and to the left of the page through the centerline of the gennou head. We will call this the “Vertical Centerline.”

Next, draw a horizontal line parallel with the Striking Face line, through the perfect center of the head’s eye (the mortise hole in the gennou head). To do this, you will need to first mark the center of the eye on the Vertical Centerline.

Begin by measuring the distance from the actual head’s striking face to the endwall of the eye closest to the striking face, and transfer this distance onto the Vertical Centerline starting from the Striking Face line using either a vernier caliper or a sharp compass.. Then measure the interior length of the eye, and add this distance to the measurement you just made. Now you have the location of both endwalls of the eye located on the drawing. Divide this line in half using your calipers or compass, and you now have located the center-point of the eye.

Be sure to precisely measure and mark these distances because if you get it wrong, problems will result.

Then draw a “Horizontal Centerline” through the center-point of the eye across the sheet, of course perfectly parallel with the Striking Face line.

Next draw two more horizontal lines from the top and bottom endwalls of the eye across the page. The width of these two lines is labeled “Eye” on the side-view drawing above.

Place the head on the drawing, with its flat face perfectly flush with the Striking Face line. You may want to lay/clamp a piece of wood along the Striking Face line make sure you get the head oriented properly centered on the vertical and horizontal centerlines you drew earlier. Then draw the outline of the head on the drawing.

Insert the wooden layout tenon you made previously into the eye, place the head back on the drawing as before, and transfer the layout tenon’s outline onto the drawing. If the eye is perfectly perpendicular to the head’s centerline then the layout tenon may not be necessary, but using the layout tenon helps to ensure the eye’s angle is accurately represented in the drawing to avoid unpleasant surprises.

Draw the Key Lines for the Top-view

Moving onto the Top View, make another horizontal line 5~6 inches above the Horizontal Centerline across the page. This line will be the centerline through the head and handle seen from above. Measure the width of the eye (the narrowest dimension), divide it in half, and transfer it to the drawing. Draw two horizontal lines from the location of the eye’s endwalls across the page. These lines are labeled “Eye” on the Top View.

Place the gennou head on the drawing and trace the outline of the striking face.

The butt of the gennou shown at the top of this article. Notice it is domed. Once again, not a sign of senility, but an intentional and entirely functional feature, the lack of which could result in the destruction of the handle during installation (seriously). Notice also how the top edge of the butt is nearly flat, while the lower edge (leading edge) is a uniform radius. These two details are neither artistic nor whimsical but have distinct functional purposes.

The head, it’s striking face and profile, the width, length and angle of the eye, the centerline of the handle in both side view and top view are all now accurately represented on the drawing. 

In the next post in this series we will measure your body and add those details to the drawing. You don’t need a Savile Row tailor for this task, but if you have one just lounging around on your couch, hogging the remote control, drinking your beer and smoking your cigs, go ahead and put the bum to work! (ツ)

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, incompetent facebook or the owners of Tik Tok and so won’t sell, share, or profitably “misplace” your information. That would be criminal.

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The Japanese Gennou & Handle Part 12 – The Drawing Part 1/6

A gennou with a modern-style 180monme head (700gm/25oz) by Kosaburo and a black persimmon handle.

A drawing is simply a line going for a walk. 

Paul Klee

This is the first of six posts in a sub-series describing why and how to make a full-scale drawing in preparation for making your gennou handle. 

Please note that the principles described in these posts on Japanese gennou handles apply to all varieties of hammer and axe handles, and can be adapted to Western tools with great success.

Why Bother Making a Full-scale Drawing?

The greatest fun in working wood as a hobby for your humble servant is watching an object evolve in my hands, sometimes magically becoming better than what I had imagined it would be. Many Gentle Readers have the same experience.

My day job in Japan’s construction industry is not so fancy free: I spend too many hours each day planning, discussing, reviewing/marking-up, and writing about complicated drawings, so drafting a drawing to make something from just a single stick of wood feels kinda silly on the one hand and too much like real work on the other. But despite these conflicting emotions, please understand I am dead serious about the importance of a drawing, and you should be too.

So why am I recommending you make a drawing? There are 3 reasons: 

Record of Ergonomic Parameters

A gennou design must begin with the fixed parameters of your gennou head, but there are several ergonomic measurements from your own body you will need to incorporate into your handle design and meld with the specific details of the head you select. This isn’t difficult to do, but because every head, every body, and therefore every handle is different, and because there are a surprising number of details that must be combined, it can be difficult to get everything right without a drawing, especially the first few times.

Develop an Elegant Minimalistic Design

The second reason for making a drawing before you make sawdust is that the gennou I am teaching you how to make is in every way a minimalistic object comprised of only two simple components the details of which require thoughtful planning to get right. 

Allow me to share a couple of points about minimalism I learned from observing the successes and failures of world-class architects and designers in New York, San Francisco, London, Hong Kong and Tokyo: When making some things, past a certain point there is simply no room for either improvisation or trial & error without starting all over again. Assuming one is not so fatuous or deluded as to accept a monkey’s scribbling as high-art, you can imagine the resulting potential for wasted time and money and brain cells.

The famous architect Frank Loyd Wright once said: “An architect’s most useful tools are an eraser at the drafting board, and a wrecking bar at the site.” Which of these tools used with skill do you think is the most cost and time effective?

Here is wisdom: The principle of “less is more” absolutely applies, but what most people not involved professionally in the design and fabrication of expensive minimalistic physical objects do not realize is that achieving an elegant and functionally superior “Less” is neither accidental nor serendipitous, but can only be consistently achieved through “ More” thought, planning, and eyeball time, something difficult to do without a drawing.

How does this apply to making a simple gennou handle, you ask? Excellent question; You really are paying attention, I see. Once you have cut or shaved away too much wood (even a single shaving can easily be too much), there can be no more thinking, planning or eyeball time without starting over, wasting much of your valuable time and wood. Best to avoid that nonsense if possible, don’t you agree?

Take a Mulligan

The third reason for making a drawing is related to the first and based on the unfortunate likelihood that your first attempt is unlikely to produce ideal results. But don’t be discouraged because your second attempt will be much better. If you begin with a drawing, by the third attempt you will have figured out precisely what works best for you, knowledge that will serve you well your entire life. I promise.

In order to accomplish the goal of the perfect handle in just two or three iterations you will need to record the measurements, assumptions and changes you made each time so you can effectively fine tune them without having to start from scratch each time. A drawing is the best tool for this purpose.

A drawing will also help you eliminate repeated errros. A drawing will also help you eliminate repeated errros.

What to Include in the Drawing

I recommend you make a full-scale drawing of the handle viewed from the side, the top (back) edge, and the butt for a total of 3 viewpoints on a single piece of paper. You should also make cross sections at several locations at the handle inside the side view.

It is also useful include general dimensions, such as overall length, width at the eye and width at the butt to help you select a suitable piece of wood.

Developing Drawing Skills

Many have no experience making drawings. That’s perfectly OK. The only way to become competent at making simple drawings using orthographic projection is to do it.

The basic idea of orthographic projection is to represent a 3-D object in 2-D drawings, usually a side view(s), top/bottom view, and end view(s), but for the purpose of drawing a simple gennou handle without power windows and tuned exhaust, a side view, top view, end view and a few simple sections are plenty.

The drawing below is one I made for one of my gennou showing just top and side views. As you can tell, it starts with the head. Sorry, no sections. I will provide more drawings beginning with the next post.

A handmade drawing for gennou hammer made to fit the author with an 85monme Kosaburo head. You can download this drawing for your reference by clicking the button below.

If you are serious about making quality objects in wood long-term, the ability to make a simple drawing is a skill you should develop. The drawing doesn’t need to be pretty, it doesn’t even need to be detailed if you are making it for your own use, but it should represent and record things like dimensions, straight line/curves, and the locations of features.

“Why can’t I just do it in my head?” you ask? Of course that is an option; There are times when we all shape wood as we imagine it, the instant we imagine it.

But a drawing lets you combine and adjust details, wait some time to grow “fresh eyes,” and examine the product. A drawing makes it easy to make fine adjustments to a minimalist object. It lets you share the design with others and get their opinion. It lets you record your successful designs for future use. It is a powerful tool, one that will improve your woodworking skills.

And with practice, the act of making drawings refines your eye and your imagination, improving not only your design ability on-paper, but your ability to create an object in your head and examine it from different angles. Just ask any second-year architecture student.

Tools for Drawing

I will go into more details about drafting tools every woodworker should own and become proficient with in a future post, but in preparation for producing the drawing we will begin in the next post, and assuming you will make the drawing on paper instead of a board, you should gather the following minimal tools:

  1. Drawing board: A plain wooden board with four straight sides and square corners at least a little bigger than the finished gennou. Any smooth, flat board will suffice;
  2. Paper: Better quality drafting paper, vellum, or mylar is best, but any smooth, white paper will suffice;
  3. Masking tape: To secure paper to board (drafting tape will damage the drawing least);
  4. Straightedge: 12″ or longer (must be truly straight);
  5. Mechanical pencil with lead;
  6. Eraser: A good quality one that won’t leave smudges;
  7. Square: A clean framing square without burred edges will suffice;
  8. Drafting Triangle: A 45° plastic or steel drafting triangle, with minimum 8″ legs (cheap is OK);
  9. Compass: With pencil;
  10. Divider: With sharp points;
  11. Vernier caliper (not mandatory but helpful);
  12. Eraser shield (not mandatory but helpful).

The Gennou Head

In this series we’ve looked at a lot of gennou heads of many different varieties and weights made by different blacksmiths. Now that we have are on the brink of making a design drawing, however, the time for talking is over. If you don’t have a good gennou head in-hand, please get one. The design of your handle simply cannot begin without it.

In the next installment in this story of love and longing we will begin our drawing. Please sharpen your pencils and get your eraser ready.

YMHOS

Can I eat your eraser? Pleeeeeease?

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, incompetent facebook, or troublesome Twitter and so won’t sell, share, or profitably “misplace” your information. May all my toes turn green and go squishy if I lie.

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The Japanese Gennou & Handle Part 8 – Head Style & Weight

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A comparison of two styles of hand-forged gennou heads. Top: A Yamakichi gennou head by Hiroki. Bottom: A classical ryouguchi head by Kosaburo with the antique “swollen eye.” Both handles are made from American Osage Orange, an excellent wood for hammer handles. The top handle still exhibits the neon yellow color typical of OO, while the bottom handle has been exposed to sunlight for a few weeks and turned a nice but unusual brown color.

Better a bald head than no head at all.

Seamus MacManus

In the previous post in this series about Japanese hammers we examined a feature found in all modern hammer heads: the essential, unblinking unseeing eye. In this post we will touch on the style of heads recommend for using with Japanese chisels. We discussed this subject in this post as well.

Gennou Head Shapes

The most common head shapes commonly available in Japan nowadays are: ryoguchi, daruma, funate, yamakichi and various hybrids thereof.

Ryouguchi

Ryouguch is the most common style of head, at least in Eastern Japan. It has two faces: A flat one for striking chisels and nails, and a slightly domed opposing face for kigoroshi and setting nails below the surface of boards.

While a simple design, this style of head has a relatively high moment of inertia, making it is more stable than other styles and therefore less likely to twist out of alignment during the swing, or twitch upon impact, a positive thing if you are a card-carrying member of NBA (Nail Benders Anonymous). (ツ)

Face designs in this style vary widely including round, oval, square, rectangular (usually with corners removed for a more octagonal shape) true octagonal, and the “Ichimonji” style with roundish sides and a flat top and bottom. We prefer the rectangular shape with cut corners best, but one style is no better than another. We don’t recommend, however, faces with 90 degree corners as the corners are counter-productive during kigoroshi operations and are structurally weaker.

If you are worried about pulling nails, we encourage you to use a nail bar to reduce the number of broken hammer handles wandering the world sad and lonely as a cloud.

A 200monme/ 750gram/ 26oz Modern-style ryouguchi gennou by Kosaburo. Notice the symmetrical shape, slightly flared ends, and the polished “hachimaki” band near each striking face.

The Daruma

Named for a famous buddhist priest of oval stature who lost both arms and legs through excessive meditation in his quest for “satori,” an intensely spiritual obsession that no doubt consumes the attention of some of our more enlightened Beloved Customers, the daruma (pronounced dah/rhu/mah) style gennou head is a stubbier version of the ryouguchi gennou, always with a round face.

This style of head is more popular outside of Japan than it is domestically, for reasons your most humble and obedient servant fails to understand. From a physics viewpoint, at a given weight it is less stable than any other style of gennou, but because it has a bigger face, and is intended to be used at constantly differing angles such that stability is not so much a virtue, it is preferred by carvers. Joiners like it too for cutting repetitive mortise and tenon joints, but it is not favored by most trades and may invite remarks at jobsites from other workers about the owner being unable to find his derriere with both hands and a GPS. That said, your humble servant frequently uses daruma heads for cutting precise mortise joints. Wait a minute…. where did I set down that darn GPS tracker….?

An 80monme/ 300gm/ 11oz daruma head with an rock maple handle.

The Funate

A funate gennou with bubinga handle.
The tail of a funate gennou. This point can be sharpened for creating pilot holes for nails when shipbuilding, or left as a rectangle of starting and setting nails. The face is slightly domed, but still flat enough for striking chisels. A good multi-purpose head that favors nails more than chisels.

The funate gennou is closer in appearance to Western hammers with a skinnier neck behind the striking face, but without the split-tail “piano chisel” a foreman from my misspent youth named Jack Frost called the claw on his 28oz waffle-face framing hammer. It is more commonly seen in the Western Japan than Eastern Japan where I learned Japanese woodworking.

This gennou is useful for finish work involving nails and for tapping-out plane blades, but less useful for wacking chisels.

The Yamakichi

Yamakichi was the name of a gennou blacksmith working in Fukuoka on Kyushu Island that originated this style of head and gave it his name. “Yama” 山 means “mountain” and “kichi” 吉 means “luck” or “lucky.” Kosaburo introduced this style to Tokyo in response to customer demand and with Yamakichi’s permission, we are told, improving the design somewhat.

This style is a heavy-duty stubbier version of the funate with a slightly domed face and a kinda sorta pointy tail, perhaps better suited to driving/setting nails than the ryouguchi head, but certainly better for striking chisels than the funate style.

Better with nails than the ryouguchi style, this head makes an excellent all-round hammer for working in the field, and can even handle tapping-out and kigoroshi tasks.

The design has a unique and interesting appearance which reminds this humble scribbler of a 1956 Ford F100 truck in that, while neither sleek nor smooth, it has a sculptural quality not seen in the other styles that “grows on you.” It feels good in the hand.

There are other in-between head shapes, but these are the four basic styles generally available for woodworking today.

Another view of the Yamakichi gennou pictured at the top of this article after the color has mellowed through exposure to sunlight. This is 300monme/375gram/ 11oz head by Hiroki has an American Osage Orange handle. (The decorative twine was added at the tool’s request. It has a thing for the color red).

Weight

The subject of gennou head weight was examined at some length in a previous post.

Regardless of the type of gennou head you select, weight is a critical factor that will depend on what you plan to hit, your height above the thing you are hitting, how hard you need to hit it, and how precisely you need to hit it. Your own practical experience is the best basis for selecting the genno weight for a particular job, but some guidelines can be suggested.

To begin, the traditional measure used for gennou in Japan is the “monme,” with 100 monme equaling 375 grams or 13.2 ounces (1 ounce = 28.35 grams). 

The standard middle-of-the-road weight for genno used by carpenters in Japan is 100monme (375grams/ 13.2 ounces). The most common hammer used for finish carpentry in the United States weighs 16oz = 120monme, a size commonly available in gennou too. So if you are going to buy your first gennou, and you intend to use it for general finish carpentry or furniture making, a 100 or 120 monme genno is a good place to start. 

For finer work, an 50-80 monme (11-7 oz) to gennou is a good choice. If you intend to make furniture or joinery, one in this weight range is a must-have.

For cutting deep mortises in heavy timbers with large chisels, as in timber framing or boat work, a 200monme (26oz) hammer is frequently used, but 250 (33oz) and even 300monme (40oz) heads are available. I own and use them when necessary. Some factors to consider when selecting a heavy gennou are that with greater weight comes greater impact force, and greater penetration, but heavier gennou are more tiring to swing and harder to control precisely.

Other factors to consider are the width of the chisel blade being used, since a wider blade requires more force to cut to a given depth, and the hardness/toughness of the wood being cut. Only experience can tell Gentle Reader what weight will work best in a given situation. Just be aware that, unlike bobby socks and government health care, there is no such thing as one-size-fits-all.

Conclusion

We hope this article has answered some of Gentle Reader’s questions on the subject of selecting a gennou head. If you have additional questions or need clarification, please use the “Leave a Reply” form below.

In the next post in this metaphysical adventure series we will discuss the differences between mass-produced and hand-forged gennou heads. We will look at woods suitable for making handles, and gennou design in much greater detail in future posts, promise.

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 by using 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.

The Japanese Gennou & Handle Part 3 – What is a Gennou?

What we have is given by God and to teach it to others is to return it to him.

Gian Lorenzo Bernini
56-1
Kiyomizu Temple, Kyoto, Japan

There are as many varieties of hammers in Japan as there are in western countries. With one notable exception, and in one specific application, Japanese hammers are not especially superior to their western counterparts. That exception is the gennou (pronounced gen-noh), a hammer intended specifically for striking chisels, adjusting plane blades, and crushing wood (i.e. “kigoroshi” or “wood killing”). This article will provide a further introduction to the gennou hammer.

What Is a Gennou?

A box-stock, garden-variety, economy Japanese gennou hammer with a one-size-fits-somebody handle

The Japanese have different terms for different hammers, of course. A hammer used strictly for driving nails, or banging sheet metal, or driving stakes is called a “kanazuchi” meaning “steel mallet.” The gennou (pronounced gen-noh), on the other hand, can be used to drive nails, but it is also suited to striking chisels and adjusting planes. The word genno was borrowed from the name of a buddhist priest who lived, or so the story goes, in the 1300’s and used a steel hammer to destroy a poisonous rock that was troubling the common folk. I’m not sure what one has to do with the other, but there you are.

The Attraction of the Gennou

Many Japanese craftsmen often have an emotional attachment to their gennou. Perhaps this is because, unlike saws, chisels, and planes that are gradually but inevitably sharpened away until almost nothing remains, or squares or making gauges that loose tolerance or wear out, a quality gennou will last for a lifetime relatively unchanged other than the occasional replacement handle. A good gennou is a simple, reliable, hardworking friend that never complains. It doesn’t have a pigtail; It doesn’t need to be sharpened. And most importantly, it will never ask a dangerous question like “do these pants make my butt look big?”

Technical Matters

The gennou is a simple tool consisting of a steel body of some shape or another and a wooden handle. The head has a rectangular hole called the “eye” in English and “hitsu” in Japanese to receive the handle’s tenon. A high-quality gennou with a good eye and a handle made by a skilled craftsman doesn’t have wedges or other silly contrivances to connect the two.

The steel used is typically designated SK, a standard high-carbon tool steel made in Japan used for making hammers, axes, and many other tools. It is very similar chemically speaking to 01 steel in the Americas. Not as pure as Hitachi Metal’s Shirogami or Aogami steel, but still completely adequate for hammers. I wouldn’t pay extra for a gennou head made from Shirogami or Aogami steel, and you shouldn’t either

Mass-produced gennou are drop-forged very inexpensively. The eyes are rough and the handles are secured with wedges. Indeed, the eyes are typically so irregular that the head will not stay on the handle without wedges. A gennou head with rough and/or irregular eyes can create unnecessary problems for the user.

“Irregular” has several connotations when talking about gennou eyes. One obvious problem is an eye that is not truly rectangular. For instance, it may have curved, twisted walls, wonky interior dimensions, or interior corners that are not square. Not only is it a pain in the tuckus to make a handle to fit an eye with these deformities, but you can bet your sweet bippy it will cause the handle tenon to loosen up sooner.

Another irregularity commonly seen in the eyes of poor-quality gennou is rough interior walls. You would think that rough walls would hold onto the tenon better, and perhaps they do compared to highly-polished walls, but rough, uneven walls tend to wear-out the tenon and cause it to loosen over time. Imagine the vibrations the tenon is forced to absorb through those walls and the grinding motion between wall surface and handle that results.

An intentional irregularity frequently seen is end walls (versus the longer side walls) that are sloped from each opening towards the center of the eye, essentially making the eye bulge inwards in the center. The purpose of these bulges is to crush the wood of the tenon when it is forced into the eye, increasing friction, while also providing a dovetail-like area for the steel wedge to expand the eye back into. It is a reasonable solution for rough, irregular eyes in low-cost hammers to be used by amateurs, but one that the craftsman that truly understands gennou and wants a lifetime tool finds undesireable. We will touch on this detail more in future posts.

Still another irregularity the careful craftsman must watch out for is an eye that is not perfectly centered in both axis in the head. You might think that an eye that is a little skewampus couldn’t make a big difference, but it does because, not only is the balance and center of mass of such a head also skewampus so that the head tends to twist during the swing and wiggle on impact, but because making handles for such a head is unnecessarily troublesome. A clean, uniform, straight, properly-centered eye is worth every penny it costs, especially if you are a professional and consider your time and sanity of any value.

A difficult question I am frequently asked is “how much irregularity is acceptable?” The answer is simple: If you think it is too irregular, then it is, because the work to correct the defect or compensate for it will all be on you.

Please understand that properly correcting major defects in hammer eyes is hard work. It takes time, concentration, a good eye, a flashlight, and a deft hand with skinny files and rulers to remove just the right amount of metal in just the right places inside that narrow eye, a task that is much more difficult than removing metal on an exposed surface because the files are thin, it’s hard to see what you’re doing, you don’t have much leverage, and consistently making a straight pass is not easy. Try it yourself and you will quickly see why.

This is the whole point of high-quality heads like those made by Kosaburo and now Hiroki and why they are worth the high cost: Their eyes are true when new, no adjustment necessary, saving the purchaser many hours of tedious work and blisters. Every time you make a handle for a high-quality head, it saves time and leaves you with a good feeling. It’s a friend. On the other hand, a poorly-made head is a curse, a money-pit (if your time is worth anything), and a frequent source of irritation (especially when the head loosens inexplicable) its entire life.

I hate to say it, but our Beloved Customers should watch out for one last defect when purchasing an expensive handmade gennou head. A perfect eye is truly a difficult thing to make, certainly more difficult than making a head cosmetically beautiful. Unfortunately, one or two famous blacksmiths (who shall remain unnamed in this series of articles, so don’t ask) have earned a reputation among knowledgeable professional woodworkers in Japan for occasionally making gennou with skewampus, eyes. Caveat emptor, baby. She may wear high-heels, a short skirt and be beautifully made-up, but if she has a curly tail and oinks she’s probably be a pig, unless she’s a boor.

If you cannot hold and eyeball an expensive gennou head before concluding the transaction, at least make sure you purchase from someone with a solid guarantee, one with no weasel-words and that reimburses you for return shipping, like C&S Tools’s guarantee does. A guarantee that you must argue about and then spend more money to benefit from is less than half a guarantee IMO.

We will delve further into the tempering and differential hardening of gennou, as well as laminated gennou heads in future posts in this series, same bat time same bat channel.

Why Use a Gennou for Chiselwork?

This is a questions we addressed in a previous post, but which we also examine further here.

Almost any striking tool, from steel hammer to leather mallet, can be used to strike a chisel. The problem is that, unless one is either gentle or the handle of the chisel is reinforced, a steel or even brass hammer will eventually destroy the handle. The solution in the West in the last century has been to use a mallet made of wood, leather, rubber, or plastic instead to cushion the blow and preserve the handle. Let’s consider this for a moment. 

The purpose for striking a chisel with a hammer is to drive the chisel into and through the wood by cutting it, right? But a soft-faced wooden mallet deforms when it impacts the chisel cushioning the blow and wasting energy through this deformation as well as generated heat. It may also waste energy through air drag, as we discussed in the Part 2 of this series. Since energy is lost, more mallet strikes are necessary, wasting time. This is demonstrably counter-productive.

Besides being relatively soft, a mallet is bulkier, slower to swing, has a huge face, and is therefore less precise than a smaller steel hammer. While there may be some that are thrilled with cutting slowly and expending extra time and energy in the process of cutting a joint, most people want to cut as much wood as possible, as precisely as possible, in the shortest amount of time as possible, and with the least energy expenditure possible. But if a chisel handle is so fragile that one must sacrifice time and energy to keep it intact, then it is only logical to conclude that there is something wrong with the design of the chisel.

Ise jingu Shrine, Mie Prefecture, Japan

The Japanese are very serious about woodworking, as anyone who has gone to Kyoto or Nara and seen the ancient wooden temples there can attest. When it comes to chisel work, Japanese carpenters don’t tolerate such silly nonsense as a chisel that must be coddled, and quite early developed a wooden-handled chisel that can be struck hard with a steel hammer all day long without breaking. 

When using a Japanese striking chisel (versus a push or paring chisel) with a hard steel hammer, as much of the user’s energy and time as possible goes into actually cutting wood. The same cannot be said of mallets made of wood, rawhide, or plastic.

The excellent design of the Japanese chisel combined with the quality of steel, and the forging and heat treatment techniques used in manufacturing most Japanese chisels provides a tough cutting edge that stays sharper, longer, placing Japanese chisels at the very top of the evolutionary pyramid of chisels. As the Japanese are wont to do, they developed a hammer specifically for striking chisels.

Most hammers intended for driving nails have a domed face which does not work well with Japanese chisels because it tends to dish out the end of the handle causing the hoop to loosen. This can even result in the handle cracking or splitting. A flat-faced hammer is much better. The Japanese double-faced genno has one face that is forged flat, for striking chisels, and an opposing domed face for driving nails or performing “kigoroshi.”

The simplicity of the design combined with these two types of faces are the primary reasons we recommend using the gennou for motivating chisels.

And while one could grind the face of a Western claw hammer flat and use it to strike Japanese chisels without any problems, the gennou is a hammer that is designed specifically for striking chisels. In my opinion, it is a superior tool for the intended purpose.

In the next post in this series we will examine three varieties of gennou to help you decide which is best for you.

YMHOS

Pagoda at Horyuji Temple, registered as one of Japan’s National Treasures.

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.

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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

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. Swear on a stack o’ bibles.

Subsequent Posts in The Japanese Gennou & Handle Series