Momi-Giri #2: Yotsume-kiri (four sided) bit

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Blog entry by aerialcopper posted 05-26-2018 08:49 PM 1480 reads 0 times favorited 0 comments Add to Favorites Watch
« Part 1: Illustration and Introduction Part 2 of Momi-Giri series no next part

Here is a simple method for making a “yotsume-kiri”, a gimlet bit for bamboo/wooden nails. For this gimlet, I wanted to use the fewest tools possible. You can see my method for making the handle here.

I used annealed 1/8” square 1095 steel key stock which cost $1.08 from McMaster Carr. Any medium or high carbon steel will make a nice bit: O1, W1, A2, 4142 all seem to be available and economical in small sizes. Even mild steel (nails, spokes, etc) would probably be fine for this style of bit, but would probably not hold up well in other styles.

Here is my fixture for indexing and holding the key stock while filing:

The tapered point needed a wedge (nail) underneath to prevent vibration. Then I filed the tang:

I dressed each face on a sharpening stone, then burnished them as I would a cabinet scraper to work a little hardness into the cutting edges.

For the ferrule, I chamfered the ID of a piece of copper tube with a utility knife, and cut off the sharpened segment with a hacksaw. Pressing the ferrule into the end grain was the sloppiest part of this gimlet, and for the next one I will probably make an alignment pin. Because the handle was turned about the bit’s point, the ferrule position doesn’t make a difference in use.

Above is my method for cutting nails of a certain length out of bamboo skewers with a cutting gauge (“wari-keshiki”). This way, I can also quickly remove the weak sections of skewer and put a nice chamfer on the tip of each nail.

I hope you’ll forgive the simplicity of this project- in any case it was a fast and satisfying tool to make. I’m building a tool box now, and will see how it fares :)

-- Dylan-

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