Introduction: Make a Yari Ganna - Japanese Spear Plane

By Made in Wood
About: Happy in wood shavings YouTube: http://www.youtube.com/c/WOmadeOD Patreon: https://www.patreon.com/WOmadeOD

Have some fun and make this ancient Japanese spear plane, a yari ganna!

You'll need:

  • 1' (300mm) of square tool steel bar stock
  • 1' x 2" x 1" (300x50x25mm) hardwood
  • wood glue
  • boiled linseed oil (or similar protective finish)
  • a forge and workshop, plus common tools

Watch me make mine on my YouTube channel, and please vote for this in the Build a Tool contest

Step 1: Forge the Blade

Refer to diagram, and proceed as follows:

  • Heat your steel up to a bright yellow/orange (working temperature) for the first two inches
  • Strike on three sides to produce a tip
  • Heat between one and three inches from the end to working temperature
  • Use a chop or chisel to narrow a circular neck area at two inches
  • Heat first three inches, and leave to air cool until back to cold colour
    (This is normalizing, and helps relieve stress from working)
  • Heat between two and four inches from the end to working temperature
  • Taper back from behind the neck, drawing two inches of bar out to a six inch tang
  • Heat at end of tang and chop off
  • Heat all of blade, and leave to air cool until back to cold colour
  • Heat tip and shape to a pointed leaf shape (see photos throughout instructable)
  • Heat again and add bevels to edges of the tip
  • Heat neck and angle tang up about 15°
  • Heat all of blade, and leave to air cool until back to cold colour, at least twice

Important - only work the steel while it is between orange and bright yellow/orange, to avoid cracks, and don't heat more than bright yellow/orange to avoid burning off carbon and melting!

Step 2: Grind and Heat Treat

Use a belt sander or grinder to flatten the back of the blade, and smooth the bevels until the edge is almost sharp

Harden: Heat from neck to tip until uniform bright yellow/orange (careful not to overheat narrow edges and tip), and quench in oil, stiring round for at least two minutes before leaving to cool enough to touch

Warning - the blade will now be brittle, so don't drop it or knock it!

Descale with a wire brush if desired

Return to belt sander to check back is flat, and to sharpen the beveled edges, cooling regularly in water so it never becomes too hot to hold in the hand (this would ruin the hardness, and cause the steel to 'blue')

Temper:

  1. Place the iron in a conventional oven at approximately 200°C
  2. Examine iron after 20 minutes
  3. If a colour change to light straw not seen, raise temperature by 5°C and go back to step 2.
  4. Leave in oven for two hours at the same temperature
  5. Turn off oven and leave iron in until fully cooled

Tempering reduces the brittleness to a sensible level, whilst retaining sufficient hardness for the tool

Step 3: Hone the Edge

Use your preferred sharpening system (diamond whetstones and strop shown) to hone a sharp edge to the blade

Warning - This is now a very lethal weapon, so do take care to avoid injury!

Step 4: Handle Part 1

We want to set the tang securely in a wide handle, and the best way I found was to rip the handle material in half, recess each half for half of the tang, and glue the halves around the tang.

Firstly saw the wood in half, length-ways

Plane the sawn edges flat and smooth, so that they meet perfectly

Step 5: Handle Part 2

Recess for the tang:

  • Draw the outline of the tang on one half of the handle
  • Create a tight recess for half the tang thickness
  • Place together with second half and secure tang in position
  • Remove first half and draw tang outline on second half
  • Create a tight recess for the second half of the tang
  • Perfect recesses, such that the handle can just about be closed around it with moderate clamp pressure

Step 6: Handle Part 3

Apply glue to the two halves of the handle and clamp around the tang, and allow to dry

Step 7: Handle Part 4

Shape the handle:

  • Use a plane to round over the cross-section of the handle, so that it's comfortable to hold
  • Plane away material behind the back of the blade, so that it doesn't protrude below the level of the back
  • Chamfer all sharp corners

Step 8: Finish and Use

The finished handle should be protected with boiled linseed oil, or similar.

I also coloured mine, before protecting, and you can see that in the video.

You're done!!

It's ready to use, and what a joy - not easy to get the hang of, but every so often a perfect, continuous shaving rolls off the edge of the blade :-)

Thanks for reading my instructable

Please vote for it in the Build a Tool contest - if you like it of course