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A Handle for a Gennou
I recently received a Tenryuu gennou head from So Yamashita at Japan Tool. This has a Tsuchime (hammer mark) finish and in the Daruma style, which is a broad head useful for chisels.
My preference was for a head weighing 375gm as this would suit both dovetail (Umeki Nomi) and bench (Chu-Usu-Nomi) chisels. I also have a lighter 225gm gennou for nails and a large 450gm gennou for heavy work ..
The head came without a handle as I planned to make one myself, and this led to some research.
Firstly, which wood to use?
The most common woods used in Japan are White and Red Oak. “King” of the woods is Gumi. Below is a beautiful Gumi handled gennou shaped by So …
I was thinking seriously of a Gumi handle when So suggested Jarrah – it has ideal properties of being hard, very tough but still retaining a little flex. Plus it would personalise my gennou with a touch of Australia!
The two best articles on handle design and construction I came across were those from So (on his website), and another from Jim Blauvelt (at the Japanese Woodworking forum).
The essential features were:
The head is attached to the tenon without a wedge.
The handle is curved to make it easier to determine the flat side of the head, which is the side used on the chisel (the domed side is used for driving a nail below the wood surface. This gennou is to be dedicated to chisel use only).
The mortice in the head of the gennou is formed with great precision. The sides are square and there is a slight taper. The correct way to fit the tenon of the handle is with the maker’s mark facing the handle as this places the taper in the correct direction…
To attach the tenon without a wedge, the tenon is made slightly oversize, then compressed by hammering on all four sides, before forcing the tenon into and through the mortice. Chamfer the end of the tenon prior to hammering it home. Finally, soak the tenon stub in oil to expand the tenon. This will create a strong joint that does not require a wedge.
Finally the handle ..
The total length of the handle is a standard 300mm (12”). This was shaped with spokeshaves and finished in oil and wax.
The curve “leans” towards the rear, which causes the head to tilt slightly away from the handle.
This is what I came up with …
Regards from Perth