Restoring the back of Japanese chisels
I acquired a few specialty chisels on a trip to Japan several years ago. One of these is a 12″ long dovetail chisel which has acquired a chipped blade. Stupidity was involved, but I now have irrefutable proof that concrete is harder than Japanese steel! I have carefully ground the blade back to square with a white 8″ Norton stone, being VERY careful not to “blue” it, but by the time I got past the chip I was already into the hollow-ground area on the back of the chisel.
My question: Is there a method to restore the flat area to the back of the chisel so that I can lap and sharpen it again? I seem to remember one article in FWW by Odate which involved using a small hammer and tapping the front of the blade just back of the bevel, holding the blade against the sharp edge of an anvil but I’m willing to look at almost any other alternative method before I resort to hitting my beautiful chisel with a hammer.
Regards,
Ron
Replies
I learned the hard way, just like you are refering to. But, to help you calm your nerves, I have never cracked a chisel. Good luck
RoninOttawa,
You can indeed tap out that hollow part on the back of your chisel. Some people with nimble fingers and a sober, steady eye do it with a hammer and an anvil--or so I've heard. I've never met such a person. Perhaps they're folklore.
Visit Japan Woodworkers' site and you'll find lots of tools they'll happily sell you to do this job. They may also have some instructions on how to do it without buying a lot of equipment. I've phoned them a few times with rank beginners' questions about Japanese tools, and they've always been very polite, very patient, and spent enough time to fully answer my questions. You might give them a call.
Alan
The back of Japanese chisels can be restored by polishing the back of the chisel on a flat piece of steel using Carborundum powder (silicon carbide abrasive) and a little water. Start with a course grit until you have ground down to a flat surface along the cutting edge. Finish with a fine grit. Once the flat surface is restored polish the back to a mirror finish. I use a very fine Japanese stone to polish the back. The back of the chisel should be perfectly flat. You can check flatness by looking at the reflection of a fluoresent light in the mirro surface. There should be no distortions in the reflection of the light.
Alternatively you could grind the back of the chisel using a 1/4" flat piece of glass and wet/dry sandpaper taped to the glass. If you have a very flat diamond stone you could also use that. The key to any good chisel is a flat back. The idea is to grind the back of the chisel down until the flat surface is resotred across the cutting edge.
Hope this helps
That chisel edge may be harder than the concrete. And much more brittle. In my experience, Japanese edge tools are made of a very hard cutting metal bonded to a softer backing metal. When my Japanese scissors were dropped on the floor the hard steel snapped. This left the scissors completely unusable and totally unrepairable. I would definately NOT hit the chisel with a hammer.
BJ
In reply to some of the other posters, I have seen a tool for "setting" the back of the chisel. I was probably 20 years ago, and I would imagine it would work. But I haven't seen one since. The process of surfacing the back is to not totally remove the concave surface, but to hammer out thea small edge of the concave surface on the cutting edge. By hammering out the edge to form a concave edge/surface, you can then surface this down to make it flat with the rest of the remaining surface.
By placing the cutting edge above a hard parallel surface by about 1/4-1/2" above, you carefully hit the soft steel of the chisel, not the hard steel of the cutting edge. The softer steel is the darker of the 2 steels. Do this only in the center of the chisel, not the outside edges. I usually hit it maybe around8-10 times. Or less when you get the feel of it. Start with hitting it lightly and then a little harder, until you get the feel of it. I use a regulat 16 oz smooth face finish hammer, nothing fancy. You only push enough steel outward on still you get small amount of concave. Once you surface this area, the surface that is at the cutting edge should be around the same with as the edges of the width of the chisel.
Another thing, don't do hollow grind the cutting facet(face of the chisel) with a grinder or belt sander. The hard steel is very brittle and a radius surface weakens the chisels ability to absorb the shock of the impact between the wood and mallet/hammer
My best suggestion would to contact Japan Woodworker and get a book on sharpening and jointery. Some of the joints are absolutley amazing
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