Used to be that bats had thick handles and a big barrel. Then they found it’s not the size of the bat that gets the home run – it’s the speed with which you can swing it.

I think I had the smallest handle around. When I got my bats, I even trimmed them down. I used to scrape them. Some years later when I started getting older, I used to start with a 33 and in the summer it got down to 31 and then probably in September got down to 30.

Stan Musial

In the previous 6 posts in this series we guided Gentle Reader in creating a drawing of a high-performance, minimalist handle to fit your gennou head and body closely. 

The handle in this drawing may not fit your body and the way you work perfectly at first; It may require adjustment, but it is a good place to start. 

Keep this drawing so you can remember what you based the original design on to help you analyze and record improvements for your next new-and-improved handle.

With the initial design complete and recorded in your drawing, the next step in this epic adventure of love, lust and sawdust is to select a stick of wood. Oh joy!

Your humble servant will not be so forward as to recommend a specific wood Gentle Reader should use. Instead, I will examine some performance criteria worthy of consideration, and only then suggest some potential candidate species.

The quotes above by Stan the Man Musial, a famous baseball player and coach that made a career swinging wood fast and with great precision, are especially relevant to the subject of gennou handles.

Please remember that, just like a baseball bat, a slender handle will not endure unless it is made from the right wood and designed to handle the forces it will encounter.

Strength & Toughness

Hammer handles are subject to relatively high impact forces in use which produce stresses and vibration, so the wood must be not only strong, as in resistant to compression, tension and bending forces, but tough. It must also have properly oriented grain.

Softer woods are easy to work and feel good in the hand, but the tenon of a gennou handle made from a soft wood such as pine, cedar, poplar or maybe even cherry, for example, will often loosen quickly as thousands of impact forces over time crush the cells.

In addition, since the fit between tenon and eye must be very tight indeed, the process of driving the tenon into the eye will not be easy. Your humble servant has broken more than one handle while attempting this. The last instance was a few years ago with a gennou handle I made from Chinese Mulberry, a wood cherished in Japan for fine cabinetry work and of which I am unreasonably fond due to it’s dramatic grain, its golden color when freshly cut, and the purplish-brown color it changes to over time. I knew it might be too weak for the job, but tried anyway. A sad waste of time and beautiful wood.

BTW, if you have the opportunity to use mulberry wood for cabinet or joinery work, by all means give it a try. I think you will be pleasantly surprised especially as the item made from the wood ages.

The material you ultimately select must be both strong and tough, but it is important to understand the difference between strength and toughness when considering materials.

The term “tough” in engineering circles means a material has the ability to absorb energy and/or forces without permanently deforming or breaking. A tough wood will still deform and bend, but when the forces that caused it to deform/bend are removed, it will return to its original shape instead of being permanently bent or breaking. In the case of a handle, if it is tough, it will flex somewhat without rupturing.

Gentle Readers are, without exception, highly intelligent, possessing a refined eye and therefore will of course be tempted to use beautiful, dark exotic hardwoods such as ebony, rosewood, bubinga, wenge, kingwood, snakewood, etc.. These are fine woods that make beautiful handles, but I don’t recommend them for a first handle due to their high cost and the likelihood that Gentle Readers will want to replace the first handle they make, and maybe even the second and third, as their skills and understanding of the ideal handle for their body and working style improves with time and experience.

And while they may have beautiful color, sexy figure, and great compressive strength, many exotic woods like ebony and rosewood may lack adequate toughness in some (but not all) cases, and crack easily. And the extra weight of such dense woods is seldom an advantage.

Your humble servant has used them successfully, and so won’t suggest they can’t make fine handles, but I simply urge Gentle Reader to be cognizant of the higher risk of failure. If you choose to use an exotic hardwood, please be especially careful of runout, a subject we will discuss below.

Friction

If you consider the vibration and angular acceleration forces acting on the gennou’s head and handle, you will understand the wisdom of choosing a wood that has a high coefficient of friction. Take my word that it is embarrassing to have the head slip off the handle mid-stroke even if no one is watching.

Oily woods like teak lack adequate friction to keep head and handle attached, in my experience. Bocote is another wood that tends to allow Murphy to slip the head off and create unplanned openings in gypboard walls. (ツ)

Stability

Another important performance criteria to consider when selecting a species of wood is that it be stable and exhibit minimal expansion/contraction with humidity changes.

If a wood that forms the tenon connecting handle to head shrinks too much when the ambient humidity decreases, the head will of course loosen.

If the tenon swells too much when ambient humidity increases, the wood cells may be crushed inside the unblinking steel eye causing the tenon to lose the ability to spring back to its original dimensions when humidity again increases, eventually resulting in a loose head. To make matters worse, the handle will loosen up even more when the humidity drops again. Murphy does backwards somersaults and clicks his thorny heels at the apex while cackling with demented glee when this occurs.

This detrimental plastic deformation is the big downside to kigoroshi in hardwoods. Let he who has ears to hear listen.

I encourage you to use a wood with a low tangential/radial expansion/contraction ratio.

The traditional way to deal with tangential/radial expansion/contraction in tool handles such as hammers and axes is to orient the rings of winter wood in the tenon in the long axis of the hammer head/eye. I don’t think this matters much with small hammers with small eyes, but it can make a difference in larger hammer heads with long eyes.

Limb Wood

It is tempting to use limb wood or orchard trimmings to make handles, especially if the grain’s curvature matches the intended design. And leaving some of the natural bark in the grip area can be interesting too. In fact, there was a period a few years back here in Japan when, probably due to the kezuroukai effect, many people were making handles from Mountain Cherry wood with the dark red bark left attached in the grip area.

This is a grand idea, especially if it means you can procure good wood for free. But for heaven’s sake don’t use such wood until it is well-seasoned and stable or you may find your wall has a new dent and your bench dog and his fleas have fled, or your bench kitty has started muttering to the iron pixies skulking in your shop about your parentage and the size of the bus you rode to elementary school. Cats are like that, you know.

Wood Grain and Runout

Grain runout is an important factor to take into account when selecting a piece of wood for a handle. A good definition of runout is as follows:

“Runout refers to the orientation of wood cells being other than parallel to the edge (face) of the board. Often difficult to detect visually, severe runout can be detrimental to strength and resistance to vibration and impact forces.”

When a board’s annual rings do not remain within the boundaries of a given pattern, be it straight or curved, the locations where the grain exits the pattern’s boundaries are called “runout.” This is an engineering term used in structural design that is applicable to selecting handle wood. In this case, it has nothing to do with the rotation of wheels and gears. Cracks tend to begin at runout locations and propagate quickly. Excessive runout can significantly reduce the ultimate strength of a board, especially when subjected to the impacts and bending forces of the sort tool handles experience. 

There are those who will dispute this structural reality, but they have done neither the engineering studies nor the destructive testing that would give their opinions value, and are herewith directed to proceed posthaste to a pharmacy to procure the salve Mifune Toshiro recommended to the tattooed criminals in the movie “Yojimbo” before educating them about pain.

Whatever wood you use, and this is extremely important, you want the grain runout to be minimal, especially in the tenon and neck. Ideally, the grain will exhibit zero runout through the tenon and neck and be curved to match the handle shape. In other words, the ideal stick of wood will have a high-percentage of fibers that are continuous from eye to butt. Such wood can be found but it may take time and effort and eye strain. Using riven wood is a traditional way to reduce runout and provide maximum strength. On the other hand, some gradual runout in the grip area is usually acceptable.

Here is wisdom: The key to judging runout is to not examine just the board, but more importantly the individual stick of wood you are considering using for a handle after it has been cut into a rectangular cross-section in preparation for layout because only when you can see all four sides the handle’s entire length will you be able to reliably judge runout. Murphy will make a fool of you if you let him.

The following link may be informative on the subject of runout: Link 1

Useful Woods

In Japan, the best traditional woods for tool handles are said to be Soraki and Ushikoroshi, both domestic ornamental bushes with white wood and plain-jane grain which are no longer grown commercially and are difficult to obtain. We have a few sticks in-stock for interested parties.

Nowadays Japanese White Oak is the standard handle wood in Japan. It is denser, stronger and whiter in color than its American and European counterparts, but the grain is quite plain.

Hickory is recognized world-over as the best generally-available material for handles, but it’s grain and color are boring. It should be easy for Gentle Readers to procure since it is sold as replacement tool and axe handles in most hardware and home centers.

Other reliable options are Ash, the various species of White Oak, Maple, and Birch, etc..

I have made several handles from Black Persimmon, a fruitwood in the ebony family, yellowish in color but with a dramatic, smoky black grain. Black Persimmon has been highly prized in Japan for hundreds of years as a wood for high-end cabinetry. The grain and color are unique.

Since around 1900, American Persimmon was considered the best wood for golf club heads because of its toughness, the “pop” it gave the ball on impact, and its relative light weight compared to its toughness. It makes a great gennou handle. I am told it is still available in some areas.

I have also made handles from American Osage Orange, a dense, stringy wood used for bows and musical instruments that makes an extremely good handle, at least once the scary neon orange color mellows through exposure to sunlight. I highly recommend it, especially if you can get it for free, which shouldn’t be too difficult in the US Midwest where it was once used extensively for fenceposts and still grows like weeds around old fence lines.

Just make sure it has reached equilibrium moisture content before making a handle from it.

Maple can make an excellent handle too. I used a stick of highly-figured tiger stripe Maple for the daruma gennou handle below, and another piece of Maple with only a little figure for the smaller daruma gennou further below.

In the next post in this series we will layout our handle in preparation for making sawdust.

YMHOS

If you have questions or would like to learn more about our tools, please click 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 all my hammer handles split!

Previous Posts in The Japanese Gennou & Handle Series

• Part 1 – Introduction
• Part 2 – Ergonomics
• Part 3 – What is a Gennou?
• Part 4 – The Varieties of Gennou: Kataguchi, Ryoguchi & Daruma
• Part 5 – Kigoroshi
• Part 6 – The Ergonomic Anaya
• Part 7 – The Unblinking Eye
• Part 8 – Head Style & Weight
• Part 9 – Factory vs. Hand-forged Gennou Heads
• Part 10 – Laminated Gennou Heads
• Part 11 – Decorative Gennou Heads
• Part 12 – The Drawing: Part 1/6
• Part 13 – The Drawing: Part 2/6
• Part 14 – The Drawing: Part 3/6
• Part 15 – The Drawing: Part 4/6
• Part 16 – The Drawing: Part 5/6
• Part 17 – The Drawing: Part 6/6
• Part 18 – Wood Selection

One accurate measurement is worth a thousand expert opinions.

Grace Hopper

As your humble servant mentioned in a previous post, and contrary to what corporate product development departments appear to assume, it is the nature of the human body for the hand to precede the hammer head during the arc of travel, with the result that, if the handle is affixed perpendicular to the axis of the head, the hammer’s face will hit the nail or chisel handle off-center and at an angle. 

In this post we will discuss this eccentric phenomenon in more detail and suggest how to compensate for it in Gentle Reader’s drawing.

The Angle of the Dangle

In evidence of your humble servant’s counter-intuitive assertions above, let us view some stop-motion high-speed photography of a shockingly ugly hammer (‘Nando is simply clucking with disapproval at the sight). 

Although the wood-butcher in this photo is using the inefficent Hobbit-basher grip, please notice the location of his pinkie finger with respect to the hammer’s face shown in this photo, as well as the angle between the hammer’s face and the nail’s axis at the point of impact seen in the last frame.

Now riddle me this, Oh Enigmatic Sphinx:

1. In this series of photos did the impact between hammer face and nail head occur in the center of the claw hammer’s face, or in the lower half of the face?
2. Was the center of mass of the hammer head in-line with the axis of the nail at the instant of impact, or was it offset?
3. Was the striking face oriented perpendicular to the axis of the nail at the instant of impact, or cocked?

Gentle Readers who answer all three questions correctly will win one-half of a day-old Crispy Creme glazed donut the next time they are in Tokyo (I get the first bite of course (ツ)). But rather than just giving out the correct answers (and risk losing half a donut!), Gentle Readers should perform the following tests themselves to gain irrefutable personal knowledge.

The Experiment & Analysis of the Results

Color the face of your hammer or gennou with a marking pen, or Dykem, then use it with a chisel to cut a mortise, without giving the hammer special attention. Perhaps a dozen blows to the chisel while it is held vertical. Then examine the hammer’s striking face and chisel handle.

Now that’s done, please examine the chisel handle. What Rosetta Stone should we use to decipher these mysterious marks?

If the ink has transferred from the hammer face to the chisel mostly dead-center, then all is well. But if it is off-center, it usually indicates two things. First, the hammer handle is either too long, too short, or your grip is goofy. Second, it may indicate that the hammer’s head is cocked at the instant of impact. More on that next. In any case, a clean impact on the end of the chisel must be our goal if we are to work efficiently (A little nod to the gods, for we are fallible, and perfection is unattainable). Therefore an adjustment to either the hammer, or the way we grip it may be called for.

Let’s take a gander at the hammer’s face next. Most people discover that the ink has been scrubbed off the bottom half of the hammer’s or gennou’s face (closest to the hand), and that the ink marks transferred to the chisel are off-center. 

If the bare spots (where the ink was scrubbed off) are not centered on the hammer’s striking face, two things are indicated: First, as seen in the photo above, the hammer’s face is probably not striking the chisel’s handle squarely, but is angled at the time of impact instead of being perpendicular. Not good.

The Consequences

Why should we be concerned about something as insignificant as an angled impact? How clever of you to ask such a intelligent question! Vector analysis suggests that an angled impact must cause the hammer to push the chisel away from the intended direction of cut, or the nail away from the intended goal (maybe even bending it). This has consequences we need to be concerned about.

The second thing these uneven marks indicate is more certain, namely that the centerline of the hammer’s head is not in-line with the centerline of the chisel’s handle at the time of impact. Once again, physics and vector analysis tells us this misalignment causes impact energy to be misdirected and wasted instead of being transmitted through the chisel to its cutting edge and into the wood being cut. The resulting feeling is a whack followed by a kick instead of a clean chopping sensation. 

Where does this wasted energy go and what does it do? It forces the chisel out of the ideal alignment and makes it feel squirrely. It beats on the hand holding the chisel. It also converts to friction heat as the blade beats on the wood instead of cutting it cleanly.

This wasted energy destroys your hammering rhythm, dulls your chisels, hurts your hand, bends your nails and makes your chisel-work sloppy. This condition can no more be tolerated than a rabid gerbil or a corrupt politician. Or is that a rabid politician and a corrupt gerbil? I forget, but it’s a difference without a distinction.

In any case, if we want the hammer’s energy to enter the chisel cleanly and motivate it to cut both efficiently and precisely, we need the center of mass of the head to be oriented closely in-line with the central axis of the chisel or nail at the instant of impact. Likewise, we need the gennou’s flat striking face to impact the chisel handle or nail head squarely, not at an angle.

Solutions

Your work with a hammer will be most efficient and precise if you meet the following three conditions:

1. Grip the hammer’s handle correctly;
2. Use a hammer with a handle length that fits your body best;
3. Use a hammer with head alignment and striking face angle that corrects the misalignment and cocking inherent in standard hammers as mentioned above.

The following guidelines should get your handle design in the ballpark.

When gripping the hammer as described in Post 13 in this series, your pinkie should just fit between the front edge of the handle and the plane of the flat striking face. The small circle drawn near the end of the hammer in the drawing is the pinkie, a dimensions that varies from person to person.

This means that if you place the gennou on a flat tabletop as shown in the drawing, and press straight down on the head so the flat striking face is flush with the tabletop, the toe of the handle will float above the tabletop with just enough clearance for your pinkie to fit between handle and table when you grip it properly.

So let’s take some more measurements and add them to our drawing.

Grip Layout

First, measure the diameter of your pinkie. Approximate is fine.

Next, we need to determine where to draw the pinkie in cross section on our drawing, but to do that we first need to measure the size of your grip. To do this, hold a hammer handle or stick in your hand gripping it lightly across your palm as described in the previous post in this series (not in a Hobbit-basher fist) with the heel of your palm and the first segment of your index finger resting on the handle’s back edge (opposite the head’s striking face), and your fingers wrapped around the handle. Use a pencil or pen to following mark 3 points on the handle or stick:

1. Make the first mark at the point where your palm’s heel ends on the handle’s back edge near the butt. Let’s call this Point 1;
2. Make another mark at the point where the first joint of your index finger begins to curve around the handle/ Let’s call this Point 2;
3. Make the third mark where the front and back edges of your pinkie finger touche the handle’s front edge. We’ll call this distance your “pinkie diameter.”

The length of the “grip” is the distance from Point 1 to Point 2.

Going back to our drawing, layout the “grip” length or “forefinger” location as shown in the drawing.

A line drawn from the top of the butt to the intersection of the grip length, as shown by the arc in the drawing below, will give you the grip angle.

Next use your divider to transfer the location and width of your pinkie finger onto the bottom edge of the drawing’s handle touching the horizontal line. Sketch a circle representing your pinkie finger in cross-section.

With the addition of these details to your drawing, it is close to being complete. I’m excited as a puppy on Christmas morning!

In the next post in this saga spanning time and the islands of the seas we will add the handle’s top and bottom edges.

YMHOS

The following link is to a folder containing pricelists and photos of most of our products. If you have questions or would like to learn more, please use the form located immediately below titled “Contact Us.”

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, thuggish Twitter, or a US Congressman’s Chinese girlfriend and so won’t sell, share, or profitably “misplace” your information. May I swallow a thousand needles if I lie.

Previous Posts in The Japanese Gennou Hammer & Handle Series

• Part 1 – Introduction
• Part 2 – Ergonomics
• Part 3 – What is a Gennou?
• Part 4 – The Varieties of Gennou: Kataguchi, Ryoguchi & Daruma
• Part 5 – Kigoroshi
• Part 6 – The Ergonomic Anaya
• Part 7 – The Unblinking Eye
• Part 8 – Head Style & Weight
• Part 9 – Factory vs. Hand-forged Gennou Heads
• Part 10 – Laminated Gennou Heads
• Part 11 – Decorative Gennou Heads
• Part 12 – The Drawing: Part 1/6
• Part 13 – The Drawing: Part 2/6
• Part 14 – The Drawing: Part 3/6
• Part 15 – The Drawing: Part 4/6
• Part 16 – The Drawing: Part 5/6
• Part 17 – The Drawing: Part 6/6
• Part 18 – Wood Selection

“This life’s hard, but it’s harder if you’re stupid.” 

George V. Higgins, The Friends of Eddie Coyle

In the previous post we started the drawing of our gennou handle using the gennou head as a template. In this post we will determine critical design details including the overall length, butt dimensions, and typical cross sections.

But first, since we are talking about making a tool we must grip in the hand, let’s consider how to hold it. You would be surprised at how many people get this simple action wrong. It matters in the context of this article because we are designing a minimalist tool for which the smallest details matter.

The Grip is the Grip

There are many ways to hold a gennou handle. The hobbit-basher grip in the fist is popular among many hammer wigglers, even those with five fingers, but it provides both low power and poor control, good for Bagginses but not so much for woodworkers.

The most efficient grip is to orient the handle diagonally across the open palm, touching the heel of the palm at one end and the pad at the base of the index finger at the other. The index finger and other fingers then wrap around and under the handle on one side, with the thumb gripping the opposite side of the handle so its is pinched between the index finger and thumb. This is similar to the grip recommended by the famous golfer Ben Hogan.

This method of holding the handle provides significant advantages:

1. The wrist is able to rotate more freely and to a greater degree;
2. The length of the hand touching and motivating the handle is much longer than the Hobbit-basher fist grip providing more leverage (couple) with less effort and more control;
3. The touchpoints at the thumb, index finger, and heel of the palm triangulate the handle in the hand and mind so the user always knows exactly where the gennou’s face is located and its angle with respect to the target without looking at or fiddling with the gennou.
4. The grip on the handle is more secure so the handle wiggles around less in the hand reducing blisters and stresses.

If you find this grip difficult, please stick with it until it becomes a good habit that displaces a bad habit.

Determine Overall Length

The next thing we need to add to our drawing begun in the previous post is the gennou’s overall length (OAL) measured from the handle’s butt (not including the dome) to the Vertical Centerline through the head’s face. This dimension comes from your body with some adjustment for how you grip and swing.

For most people, a good starting length can be measured by bending your hammer arm 90° at the elbow and laying a straightedge or folding ruler across your upward-facing palm and forearm. Touch one end of the straightedge against the tendon at your elbow and measure the distance to the base of your middle finger. In my case this 12 inches, but I’m not a big guy.

You may want to add an extra inch to your first handle. If you later decide the handle is too long, you can whittle it shorter.  Remember, the first handle you make will be experimental, and probably not a keeper. I suggest you plan on making at least three over a period of a few years and after sufficient testing to determine the ideal length for you.

As seen in the photo above, with the head held in a flat palm (not a fist), and the fingers wrapped over the head, the butt just touches my bicep tendon. In my case, by total coincidence, this is 12″. Add ¼” to the length for the domed butt; you will need it. At 5’8″ I am not a big man and have neither long arms nor big hands. Your handle may well be different.

Add this OAL dimension to your drawing.

Measure the Butt

So far we have focused on the head and overall length. The next details we need to determine are the dimensions of the butt, most importantly, its height.

The height of the butt is important not only because it determines how large the grip area’s circumference will be, but also because it partially controls the angle of the grip, and therefore the angle of the head and striking face at the time of impact.

Only you can decide what dimensions will work best for you, but since we need to start somewhere, I suggest you make the handle’s butt at least l” (25mm) wide (seen from above), and 1-⅜” (35mm) high. If you have large hands or prefer a large grip, or are using a heavier head, then the flat area should be wider to reduce pressure on the hand.

Reaction Forces

Next let’s consider the forces acting on the handle and the user’s hand, and their influence on the hammer’s performance and user’s comfort and endurance.

Commercial handles typically have a symmetrical oval cross-section that looks good, is easy to manufacture, and is consistent with the one-size-fits-nobody philosophy convenient for mass-production and mass-marketing. Sadly, this oval cross-section ignores the three reaction forces that act on the user’s hand. 

The first reaction force occurs when the user brings the hammer up in preparation for a strike. In this case, a force couple (matched forces) presses the handle into the first joints of the fingers and the heel of the hand (assuming, of course, one is gripping the handle as recommended above and not like a demented mountain troll).

The second reaction occurs when the hammer reaches the top of its swing and the user changes the direction of the hammer head towards nail or chisel. A force couple presses the handle against the first joint at the base of the user’s index finger, and the tips of the other fingers. The pinkie finger has a major role in retaining the user’s hold on the tool, you will notice.

The third reaction occurs when the speeding hammer head impacts nail or chisel and the handle kicks back at the user’s palm and fingers, just as Sir Isaac Newton predicted.  

If these reactions are balanced to the object being struck/cut by the weight and speed of the hammer, this cycle can be smooth and efficient and the kickback forces minimal. But if the hammer is too heavy, or too light, the forces the user must apply to the hammer and the force and pressure of the resulting reactions can be become tiring and even bruising. A good handle made to fit the head and the user’s body and hammering technique will improve efficiency and reduce wear and tear on the user’s body.

What is this wear and tear you say? All the aforementioned reaction forces cause the handle to kick the muscles, tendons and bones in the user’s hand, and can cause bruising. Even if it doesn’t bruise, after a long day of chiseling the hand wielding the hammer will be more worn and tender than when the day started.

Even if you never grow tired and pain means nothing to you, Oh Master Blaster, these reaction forces tend to push the handle out of alignment in the user’s hand shifting the next hammer stroke slightly off-line, and twisting the hammer’s face slightly out of ideal alignment. Have you ever noticed how the hammer becomes wobbly after a couple of blows in quick succession? Guess why that happened.

Back-edge/Top Cross-section: Flat

The solution to these troublesome physics problems is simply to make the top/back edge of the hammer in the grip area more-or-less flat instead of round or oval, a modification that will spread the reaction forces more evenly across your hand, preventing bruising and reducing fatigue. It will also stabilize the handle in your hand improving unconscious alignment and reducing twisting.

You have probably never seen a handle shaped like this much less used one. It may look uncomfortable in your mind’s eye or on paper, but it is comfortable in-use. Try it before you dismiss it.

Another big advantage of the flat on a hammer handle is one you have probably never thought about, but the lack of which has wasted much of your time while using hammers. When doing woodworking especially, we tend to set our hammers down while we change position, move the workpiece, or remove chips. Often, we don’t recall the angle or direction we set the hammer down, so when we pick it back up we must double check two things by eye: First, where our hand is located on the grip, which distance of course determines how far the center of the striking face is from our hand; and second which face/ claw of the hammer is facing which direction.

I don’t know about you, but I want my hand to learn this information and get the hammer oriented properly without my having to take my eyes or attention away from the work at hand. Anything else is stupid.

The flat immediately tells your hand which direction the striking face is oriented, and where your hand is located on the handle, all without using your eyes or giving the matter a single thought. It’s a psychic handle, sorta (ツ)

Front-edge Cross-sectional Shape

While the top/back of the handle is more or less flat, as seen in the photo above, the lower/leading edge (surface facing the chisel or nail) should be circular at the butt, gradually transitioning to a flat surface as it nears the eye. Some people like this surface to be egg-shaped. I prefer a simple circular radius. For your first gennou handle, I recommend you begin by making it a simple circular radius and shave and whittle it to fit your hand more precisely later.

The reasons for making this surface rounded are simply to maximize the surface area of contact between hand and handle, and to make the grip comfortable.

Put all this into a simple sketch and transfer it to the drawing. At this point the end view of the butt should be shaped like a pregnant letter  “D” with the curved surface oriented downwards towards the bottom of the page of the profile drawing.

Side Surface Cross Section: Flat and Parallel

So far, we have determined the back/top edge will be mostly-sorta-kinda flat, and the front edge will be more-or-less rounded. Next, let’s examine the two side surfaces.

Looking at the butt in cross-section, the handle’s right and left sides should be perpendicular to the flat on the handle’s back/top edge (plan view). These curved-plane surfaces begin at the head’s eyes, and curve down the handle all the way to the butt with some radiusing and softening of course.

Please note that, unlike commercial wooden hammer and axe handles that need a goofy flair below the eye to keep steel wedges from splitting the poorly-made handle, this minimalist gennou handle does not. It is an elegant, handmade craftsman’s tool, not a nail-bender or cockroach killer, and simply doesn’t need wedges.

Instead of a cancerous bulge, the handle remains a few shavings thicker than the eye for some distance until it smoothly flairs into the grip area. This design has serious advantages we have discussed in earlier posts in another series about what hammers to use with chisels, which I will briefly summarize.

1. A minimalist, thin handle has less air resistance wasting less energy, a serious concern in a tool moved as quickly as a gennou;
2. A thin handle transits fewer shocks and vibrations to the user’s hand;
3. A thin handle is easier to pinch between index finger and thumb providing maximum control in the Ben Hogan golf club grip;
4. If and when the handles loosens (it’s only wood after all, not eternal Chinese-made plastic-covered bent sheet metal), the user can tap the handle further into the eye quickly tightening the handle without pausing work. Note that this is not necessarily the ideal permanent fix, although it certainly can be.

Some will look at the thin handle and fear it will break. This is always a possibility with any wooden handle, but your humble servant has never broken a properly-made gennou handle, although I have broken plenty of commercial hammer handles. The key is to make your handle from the right wood, with proper grain orientation and minimal runout (we’ll talk more about these details in future posts), and to always use the head, not the handle, to drive nails and wack chisels. Duh.

We will talk about these specifications and details in future posts in this story of crime and passion.

In the next post we will determine the angle between the head and the handle. If you think this angle is unimportant then you’re in for a big surprise.

YMHOS

PS: We will provide a comprehensive document covering all the steps of making a gennou handle to our Beloved Customers (may the hair on their toes never fall out) upon request.

The following link is to a folder containing pricelists and photos of most of our products. If you have questions or would like to learn more, please use the form located immediately below titled “Contact Us.”

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, thuggish Twitter, or a US Congressman’s Chinese girlfriend and so won’t sell, share, or profitably “misplace” your information. May I swallow a thousand needles if I lie.

Previous Posts in The Japanese Gennou & Handle Series

• Part 1 – Introduction
• Part 2 – Ergonomics
• Part 3 – What is a Gennou?
• Part 4 – The Varieties of Gennou: Kataguchi, Ryoguchi & Daruma
• Part 5 – Kigoroshi
• Part 6 – The Ergonomic Anaya
• Part 7 – The Unblinking Eye
• Part 8 – Head Style & Weight
• Part 9 – Factory vs. Hand-forged Gennou Heads
• Part 10 – Laminated Gennou Heads
• Part 11 – Decorative Gennou Heads
• Part 12 – The Drawing: Part 1/6
• Part 13 – The Drawing: Part 2/6
• Part 14 – The Drawing: Part 3/6
• Part 15 – The Drawing: Part 4/6
• Part 16 – The Drawing: Part 5/6
• Part 17 – The Drawing: Part 6/6
• Part 18 – Wood Selection

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 Gentle Readers may find the idea of making a drawing in preparation for fabricating something as apparently simple as a handle from a single stick of wood nonsense. 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 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 forged 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

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 be touching this line.

Gennou heads usually have a maker’s brand stamped into the steel adjacent the flat striking face. Please orient this brand closest to the “Striking Face” line.

You can of course orient the brand facing either the butt end or the tenon end of the handle. In Japan the standard convention is the butt, making the brand a little less visible. Some Westerners prefer the opposite orientation because, I assume, they want the brand to be immediately visible. This is understandable and entirely practical, but from the viewpoint of the Japanese craftsman it is akin to using underwear as headgear. To each his own.

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 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

The following link is to a folder containing pricelists and photos of most of our products. If you have questions or would like to learn more, please use the form located immediately below titled “Contact Us.”

Please share your insights and comments with everyone by using the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, thuggish Twitter, or a US Congressman’s Chinese girlfriend and so won’t sell, share, or profitably “misplace” your information. May I swallow a thousand needles if I lie.

Previous Posts in The Japanese Gennou & Handle Series

• Part 1 – Introduction
• Part 2 – Ergonomics
• Part 3 – What is a Gennou?
• Part 4 – The Varieties of Gennou: Kataguchi, Ryoguchi & Daruma
• Part 5 – Kigoroshi
• Part 6 – The Ergonomic Anaya
• Part 7 – The Unblinking Eye
• Part 8 – Head Style & Weight
• Part 9 – Factory vs. Hand-forged Gennou Heads
• Part 10 – Laminated Gennou Heads
• Part 11 – Decorative Gennou Heads
• Part 12 – The Drawing: Part 1/6
• Part 13 – The Drawing: Part 2/6
• Part 14 – The Drawing: Part 3/6
• Part 15 – The Drawing: Part 4/6
• Part 16 – The Drawing: Part 5/6
• Part 17 – The Drawing: Part 6/6
• Part 18 – Wood Selection