How to Sharpen Japanese Chisels
On no account use a dry-running grinding machine. Even wet-running grinders are little suited to this tool, as the bevel they make is hollow and will weaken the cutting edge. The best thing to use is a Japanese waterstone.
Flatten the face of the chisel first - always an absolute necessity for new chisels. Rest the blade with the face of the chisel flat on thegrinding surface (either an absolutely flat stone or a steel plate with silicon carbon powder scattered on it), and move the blade over this surface until you can be sure you have taken a little off the entire cutting area. Do not grind to much of the face of the chisel away, or the hollow will be too much reduced and later honing made more difficult.
The next thing is to grind the bevel on a waterstone (grain size 600 to 100). For Japanese blades, the correct angle is slightly less acute than for European ones. Take about 30° for soft woods and even up to 35° for hard woods.
Hold the chisel in your right hand. Push several fingers of your left hand (depending on the breadth of the tool) onto its face, right down by the bevel, so that its surface is pressed close and firm against the grinding stone. It is then possible to use your thumb to give the tool support from underneath. The best cutting edge is obtained by running the blade along the stone at either 90° or 30° to the direction of grinding.
However, very narrow chisels (with cutting edge shorter than the length of the bevel) are an exception to this rule. Hold such tools in your right hand, as far back as possible on the handle, and while sharpening push them with the blade backwards and forwards. Using a grinding feed is perfectly legitimate - and is strongly recommended for beginners. Continue the sharpening process until a fine burr is produced on the edge.
Now - but not before - you can start actually to hone the blade. Take a stone with a grain size between 3000 and 8000, and grind the bevel and the flat face of the chisel alternately, several times, exactly as described above. The burr will fall away; the bevel and the face of the chisel will shine ever brighter as they become sharper and sharper.
Take care to dry the tool thoroughly after sharpening and, if then storing it, to oil it lightly so that corrosion does not set in. You will long have pleasure in your valuable tool.
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