Dumb Japanese Chisel Question

[Michael O'Sullivan]

If you grind the chisel to the point that you start to run into the hollow in the back, is it "sayonara" to the chisel? Or is there something obvious I am missing?

[Mike Henderson]

I'm far from an expert on Japanese chisels but from what I understand there are two ways to deal with the problem.

The first is to grind the back down in the same fashion that you would flatten the back of the chisel. As you grind the back down, you're making the hollow less deep and you'll have a straight front edge.

The second technique involves tapping on the top front edge of the chisel with a hammer to push the metal downward, making the front of the hollow less deep.

I've never used the hammer technique so I can't give you any tips. People have told me that there's a risk of fracturing the hard steel in the edge when using that method. Maybe someone who knows more will comment.

Mike

[David DeCristoforo]

Can't add much to what Mike said except that the "tapping" method is usually reserved for plane blades and larger chisels. With smaller chisels the backs are usually just reground. Eventually, whatever the size of the blade, this will "thin" the hard steel layer so tapping out the edge is the preferred method. If you want to try this I can give you some direction but it would be best to practice on a "cheapo" blade because, as Mike pointed out, you can crack the hard steel if you hit the bevel in the wrong spot or hit it too hard.

[Mark Singer]

I don't hollow Grind Japanese chisels, I flat grind them with waterstones, Curved meeting curved doesn't work well

[Derek Cohen]

If you grind the chisel to the point that you start to run into the hollow in the back, is it "sayonara" to the chisel? Or is there something obvious I am missing?

Michael, I'm afraid that once you get to the hollow it is over. I am one of the world-wide official Japanese chisel disposal experts, so send all your used up chisels to me. I will give them a good farewell.

You should never actually get to the hollow. The act of polishing away the wire edge will also polish some of the chisel back. This will be sufficient to keep the hollow moving back and away from the bevel edge.

Regards from Perth

Derek

[Wiley Horne]

Michael,

What Derek said--you won't get there, just with normal sharpening procedure. In fact, the greater problem is overdoing the back out of fear that you will get to the hollow. What happens when you overwork the back is that you start getting fat corners and you're quickly sharpening away the hollow.

So take it easy on the back. One way you can do this is don't touch the back with your 1000g stone after the initial flattening. So when you sharpen, use the 1000g and the middle stone on the bevel, and don't even back off until you're done with the middle stone or well through it.

This same procedure doesn't work on Japanese plane blades, because they're hollowed more deeply, and you will definitely reach the hollow on them, and they have to be tapped out. I should also mention that many advanced practitioners will tap out chisels for various reasons, but in general it is not necessary, and it is best not to learn to tap out on your new chisels--a bad hit will crack the cutting steel (hagane), and it's easy to make a bad hit when learning. You want to learn on beaters.

Wiley

[Frank Drew]

Michael,

Are you regularly sharpening your chisels by "grinding" the bevels on a flat stone, or on a grinding wheel?

The latter isn't a method I'd ordinarily use with Japanese chisels, barring a big nick in the edge that can only be removed in any reasonable amount of time with a wheel.

[Michael O'Sullivan]

Michael, I'm afraid that once you get to the hollow it is over. I am one of the world-wide official Japanese chisel disposal experts, so send all your used up chisels to me. I will give them a good farewell.

They have been raising postage since gas went through the roof, so I can't afford to send my chisels to Oz. I'll probably just give them to the neighbor kids for their knife fights.

More seriously, thanks for the responses. I suspect I am overestimating the depth of the hollow.

[Wilbur Pan]

I don't have anything to add to the excellent advice given above, but I do have a picture to show you what you can expect.

http://farm4.static.flickr.com/3120/2574680922_f0db0c7fec.jpg

The chisel on the left I bought used, but as you can see, the previous owner was pretty enthusiastic about grinding the back, as the flat area between the edge and the hollow is pretty wide. This chisel had much more grinding on the back than was necessary.

The chisel in the middle was a used chisel where the bevel was ground into the hollow when I got it. After working on grinding the back on a waterstone, you can see a really thin area of flatness between the hollow and the edge of the chisel. But now this chisel is useable.

The chisel on the right is fairly new, so the amount of flat area is a little generous, but this is closer to what your goal is. Actually, for sharpening this chisel, I would probably just work on the bevel side until I almost got to the point of the chisel in the middle before starting to work on the flat side of the chisel again.

Hope this helps!

[Pam Niedermayer]

You may want to check out http://www.woodworkforums.ubeaut.com.au/showthread.php?t=47840
for some neat graphics and instructions on sharpening Japanese chisels.

Pam

[Frank Drew]

Thanks for the link, Pam; I hadn't seen that site before.