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.

Gennou Handle Drawing 20201010

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

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

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

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

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

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

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

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

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

Draw the Key Lines for the Top-view

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

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

The 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

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