The Japanese Gennou & Handle Part 18 – Wood Selection

Stanley “Stan the Man” Musial, one of baseball’s greatest players and most consistent hitters.

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 a tenon 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.

Chinese Mulberry Wood

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 with 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 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 horny 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 take notice.

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 cat starts 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 to find. 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.

A Hiroki head with a Ushikoroshi wood handle

Nowadays Japanese White Oak is the standard handle wood in Japan. It is denser and 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.

Black Persimmon Planks

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.

A Kosaburo Classic-profile head with a Black Persimmon handle
A Kosaburo Modern-profile head with a Black Persimmon handle

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.

Top: A 100monme Hiroki Yamakichi head with a new and shockingly-colored American Osage Orange handle. Bottom: A 60monme Kosaburo Classic-profile head with a mellowed American Osage Orange handle.

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.

A 80monme Hiroki Daruma head with a tiger maple handle (side view)
A 80monme Hiroki Daruma head with a tiger maple handle (face)
A 60monme Hiroki Daruma head with a tiger maple handle (side view)
A 60monme Hiroki Daruma head with a tiger maple handle (face view)

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

YMHOS

Stan the Man Musial. Please notice the skinny bat he used with great success.

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 the angry fleas of a thousand camels infest my armpits.

Previous Posts in The Japanese Gennou & Handle Series

The Japanese Gennou & Handle Part 17 – The Drawing Part 6/6

Dom Campbell’s in-progress atedai, and a few of the tools he used, including a most excellent gennou with a Kosaburo head and a handle he made himself.

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.

Stan Musial

In the previous five posts in this sub-series about making a drawing for a high-performance custom gennou handle, we measured various dimensions and incorporated them into our drawing. In this post we will bring everything together, and then discuss some of the strange features of this design, including a physics equation that drives it.

During this phase of the handle-making process you will have another opportunity to express the minimalist artiste lounging stylishly within your soul, probably wearing a cravat and sipping espresso languidly. C’est Magnifique!

The Sides

Let’s start work by drawing the butt’s width, determined in the previous post, on the plan view (upper half of the drawing above) centered on the handle’s centerline.

Next, once again in the plan view (upper half of the drawing above), draw two lines from where the tenon exits the eye to the butt.

Beginning at the grip area, draw curves from these two lines to to the right and left sides of the butt in a smooth transition, gradually expanding in width. The curvature/flair you produce will depend on the size of your grip, the width of the butt, and your sense of what makes a beautiful line. Feeling artistic yet? More espresso please.

Whither the Bulge?

Gentle Readers will have noticed from the drawings and photographs seen in this series so far that, unlike commercial handles, the handle we are designing does NOT exhibit a cancerous swell just below the eye. This is not a mistake. Remember, we are making a lean, mean, racing machine, not a nail bender with a sloppy eye and mass-produced tenon that needs wedges to hold it together.

This shape, with its narrow neck, flare towards the butt, and lack of the typical bulge below the eye strikes most people as strange, so an explanation may be useful.

To begin with, Japanese gennou heads of the quality assumed in this article are not secured with wedges, but by an extremely tight fit between the wooden tenon of the handle and the surfaces inside the precision-forged eye. Indeed, the fit should be so tight that, if by accident or some terrible oversight, one attempts to drive the tenon of a handle made from a wood too weak for the job into the head’s eye, the handle and/or tenon will fracture. Your humble servant has done this several times. Such a tight fit does not occur by accident. Wedges could only weaken the tenon and handle causing early failure.

To ensure this fit is indeed tight and secure, Gentle Readers must prepare the eye if the head is of lessor quality than the Hiroki or Kosaburo heads we carry, as described in previous posts in this series. If that work was necessary, we will assume it has already been completed.

Gentle Readers must use a strong, tough wood suitable to the task. The selection of wood will be the subject of the next post in this series.

They will also need to create a properly sized tenon on the handle’s end. These are critical points.

Because it is a craftsman’s hammer, not a wood butcher’s maul, there are no wedges to split the handle, and therefore no need for a tumor below the eye to both reinforce the sloppily-made handle and to keep the wedge from pushing the head down the handle.

Indeed, without the cancerous bulge, if the handle loosens sometime in the future, tapping the handle further into the eye will tighten it up, something a bulge would make impossible. Best to eliminate unsightly, unnecessary bulges entirely.

Air Resistance

Your humble servant has previously suggested that the handle we are designing will be a “high-performance tool,” indeed a “racing machine.” While not in the same class as a Formula-1 race car, air resistance is definitely a factor affecting performance, one impeded by an unnecessarily large hammer face, a thick, obese handle, and a bulge below the eye as is typical for commercial handles.

Why is air resistance an issue, you say? Of all the hand tools used in woodworking, aside from the long-handled axe, the hammer is the one that moves the fastest, and since air resistance varies with the square of the object’s velocity, hammers and axes are impacted by air resistance more than any other hand tools. Remember, we are talking about energy created by your body that is wasted by pushing air around unnecessarily.

For those Gentle Readers that enjoy math, the formula for calculating air resistance includes the area of the object, a drag coefficient specific to the object’s shape, and the object’s velocity squared. 

F = Force due to air resistance, or drag (N)

k = A constant that combines the effects of density, drag, and area (kg/m)

v = The velocity of the moving object (m/s)

ρ = The density of the air the object moves through (kg/m3)

CD = The drag coefficient, includes hard-to-measure effects (unit-less)

A = The area of the object the air presses on (m2)

We can’t control air density.

The total CD drag coefficient is a combination of the CDhead of the head and the CDhandle of the handle. We can reduce this combined Total CD by using a more aerodynamic steel hammer head instead of a huge, silly mallet, and by reducing the area of the handle pushing the air aside during the swing. I haven’t made the calculations, but the energy squandered by the excess drag of an obese handle over thousands of swings during a day’s work is not insignificant.

Another advantage of a slender neck on a hammer handle is the surprising reduction in vibration transmitted to the user’s hand, saving wear and tear on joints. This alone makes it a worthwhile improvement in my experience.

But all is not blue bunnies and fairy farts, I fear, for there are two downsides to a skinny super-model neck on a handle. First, if you tend to miss a lot when driving nails, errant heads may chew up the handle in an area where there is not much material to spare. Gentle Readers would be fully justified in blaming this damage on the malicious malfeasance of pixies, or the luck of Murphy, but my advice is: don’t miss.

The second downside to a slender neck in a gennou handle is that it’s inconvenient for choking-up on. But on second thought, that’s not a disadvantage to anyone except mountain trolls and grannies, bless their fluffy-white souls. The solution? Don’t choke up on the handle; The grip is the grip.

All Choked Up

Commercial hammer handles are a one-size-fits-nobody design, intended to accommodate many grip styles, apparently by many species, along most of the handle’s length. Holding the hammer like a hungry troll tenderizing a dwarf for the stewpot (perhaps with a delicate sprinkle of sage or a more bold glob of “floater” spice), and choking up on the grip like a near-sighted grandmother is the lowest-common-denominator design standard for commercial hammers, a crude detail simply not to be borne by C&S Tool’s Beloved Customers and the exceedingly refined Gentle Readers of this blog.

“They should be grilled and sautéed with a sprinkle of sage”

The ultimate goal of this exercise is to produce a hammer that fits Gentle Reader’s body perfectly, not every Tom, Burt or William that staggers into The Home Despot from the Ettenmoors. It will fit your arm, and your hand, and you grip without choking-up on it.

What’s wrong with choking up on the handle? Did I just hear you say: “If it’s good enough for Granny it’s good enough for me?” If so we may need to procure more of the salve Mifune Toshiro lamented not having.

Choking up on the handle is inefficient for two reasons. First, because it changes the balance of the hammer and your working rhythm (pendulum physics). This is bad.

Second, when you choke up on the handle, for at least a couple of strikes you lose the sense of the distance from your hand to the striking face’s center, reducing both your precision and confidence, and the energy imparted to the chisel or nail. Reestablishing the correct distance in your mind requires a glance at the hammer, an adjustment in your head, and an interruption in your hammering rhythm. All this nonsense is easily avoided by gripping the handle in the same location every time.

You have basically designed most of the grip’s details when you set the butt’s shape and dimensions, and the location of your palm’s heel, index finger, and pinkie finger. I suggest you leave well-enough alone for now, and, assuming this is your first custom handle, make it a tad oversized at first, and then whittle, shave, and sand it as you use it until it fits you perfectly.

In the next post in this series we will select a piece of wood from which to make our craftsman’s gennou handle. Soon we will be making sawdust… how exciting!

YMHOS

If you have questions or would like to learn more about our tools, please see the “Pricelist” link 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, facist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may the angry fleas of a thousand camels infest my armpits.

Previous Posts in The Japanese Gennou & Handle Series

The Japanese Gennou Hammer & Handle Part 16 – The Drawing Part 5/6

The Christian does not think God will love us because we are good, but that God will make us good because He loves us.

C.S. Lewis

In this post we will continue working on the design drawing of a craftsman’s gennou hammer handle designed and made to specifically fit Gentle Reader’s body and way of working.   

We will layout the top and bottom of the grip area, and include clearance for Gentle Reader’s pinkie finger. The resulting curvature will ensure the striking face will be in proper alignment with either chisel or nail when in use, providing improved accuracy and efficiency, while reducing stresses on joints.

Adding the Top and Bottom Edges

We touched on the shapes of these edges in a previous post, but the time has come to add the lines to our drawing. In a previous post, we extended the two lines in the side view drawing from the eye straight back towards the butt.

With the butt sketched on the drawing with the lowest edge of its downward-facing radius just touching the head’s “striking face plane,” draw an arc the length of your grip from the heel of your palm to the second joint of your index finger, with the compass’s leg pivoting on the intersection of the overall-length line, and top edge of the butt.

Then draw a straight line between the intersection of the OAL line and butt’s upper edge and the top line that you extended from the eye previously. This line will be angled downwards toward the butt.

Next draw a straight line from the intersection of the OAL line over and just touching the pinkie finger circle, until it intersects the bottom line extended from the eye. Combined with your body, and nature of your individual swing, the angle of this line will determine the angle of the head at the point of impact.

Since everyone is different, only you can decide what angle works best for you. These guidelines are a good place to start, but understand you may need to modify or remake the handle until you find the angle that works best for you. By recording the angle in a drawing each time you can adjust it to find the angle that works best for you.

Now smooth out the transition of these lines into a smooth curve, with all edges relieved and radiused, but without making the top edge of the grip area too rounded.

Some people prefer to make these lines and the handle more or less straight, and to change the angle at the point where the handle exits the head’s eye. This is entirely acceptable, but realize such a design depends on really tough wood with interlocked grain or an unusual kink in the grain direction to avoid eventual failure.

I prefer to deal with this change in angle by using a smooth curvature instead. I think it looks better. I know it fits my hand better. It is easier to find wood with a gradual curvature than kinked grain. And my engineering background tells me that I want to avoid sudden transitions that induce stress concentrations, especially where steel meets wood and when grain runout is possible. But it is your decision.

Draw the curves with a pencil, then erase and redraw, erase and redraw until it looks right. 

In the next post we will add the handle’s sides to our drawing.

BTW, links to all the published posts in this series are located below.

YMHOS

If you have questions or would like to learn more about our tools, please see the “Pricelist” link 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, facist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may the bird of paradise fly up my nose.

Previous Posts in The Japanese Gennou & Handle Series

The Japanese Gennou & Handle Part 15 – The Drawing Part 4/6

Statue of Filippo Brunelleschi, the father of technical drawing and linear perspective, and both architect and builder of one of the largest and most magnificent domes in the world. Thanks, Maestro Brunelleschi, for teaching us how to draw! But what’s up with pokin holes in pizza dough…?

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 (perfection is unattainable), so 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 the angled impact must cause the hammer to push the chisel away from the intended direction of cut. 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 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 reduces your cutting precision, destroys your hammering rhythm, dulls your chisels, hurts your hand and bends your nails. This condition can no more be tolerated than a rabid gerbil or a corrupt politician. Or is that a rabid politician and a stinky 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 the chisel 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

Christmas Cheer Christmas Is Coming GIF - ChristmasCheer ChristmasIsComing Excited GIFs

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

The Japanese Gennou & Handle Part 14 – The Drawing: Part 3/6

Top: A 100monme (375gm) gennou head by Hiroki mated to a new Osage Orange handle. Bottom: A 60monme (225gm) Kosaburo classic ryouguchi head joined to a mellowed Osage Orange handle. The difference in the size of the eyes and weights of the heads combine to make handles of different dimensions. Therefore the design begins with the head.

“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 the gennou or fiddling with it.
  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.

A classic Kosaburo gennou head mounted to a 12″ osage orange handle.

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

In the case of this Yamakichi gennou by Hiroki, the striking face is is towards the right side of the photo. Please notice the shape of the handle with respect to the striking face.

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 stuff. 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.

A confused, lost Hobbit basher. And just look at that dried-out skin! Won’t you please help him find his way back to a dark, damp forum somewhere? A stop-off for a pedicure and a moisturizing treatment would not go amiss.

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

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 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

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 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 eye 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 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)

A Dandy leaving Saville Row in a sharp morning coat. The extra hand is that of his out-of-frame bride and not a birth defect. Please notice that his head covering does not resemble underwear.

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

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 minimalist 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.” When used with skill, which of these tools 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 minimalist 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 avoid repeated errros. A drawing will also help you avoid 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

So far 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?

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, facist 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

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

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, facist facebook, thuggish Twitter, or a US Congressman’s Chinese girlfriend and so won’t sell, share, or profitably “misplace” your information. May toes all grow black, stinky mushrooms if I lie.

The Japanese Gennou & Handle Part 2 – Ergonomics

A Kosaburo hand-forged gennou head hung on a Black Persimmon handle. This was the first professional-grade hand-forged gennou head I purchased many moons ago.

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

Professor Marshall McLuhan

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 I encourage them 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 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 bent nail, 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 forcing ourselves to adjust our grip and swing to fit standard one-size-fits-nobody hammers.

A lot of blowhards and marketing departments give lip-service to so-called ergonomics, but not here at C&S Tools, my good man. 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.

Three 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 blister-maker 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

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, facist facebook, thuggish Twitter, or a US Congressman’s Chinese girlfriend and so won’t sell, share, or profitably “misplace” your information. May dogs and puppies forever hate me if I lie.

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 (written 玄翁 in Chinese characters and 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 kings did 200 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 the prevalence of craftsmen purchasing pre-manufactured things, including tool handles, many of which they would have made for themselves as a matter of course.

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 containers 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 precisely, make your joints hurt less, 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 is a series of performance tests listed in the last post of this series (when it is published, see link at the end of this post) 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 fitted 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 efficient 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, thank 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 needlessly-curved 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.

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, facist facebook, thuggish Twitter, or a US Congressman’s Chinese girlfriend and so won’t sell, share, or profitably “misplace” your information. May I never know love or sunshine if I lie.

Subsequent Posts in The Japanese Gennou & Handle Series