Japanese blade "tapping out" disaster

[Stanley Covington]

Stan Covington mentioned that he had chipping problems with a mosaku plane that he got based on my comments, and I think he's cursed my plane, too!! The last time I used it, I had tiny chipping issues with it, and combined with its hardness, that can make for an undesirable session.

My experience with yamamotos (having had 3) is that they are somewhere between in hardness. They are not as hard as the mosaku iron, but the ones I had (not swedish) were not exactly soft, either.

Sorry to hear your Mosaku is misbehaving, David. Mine has settled down and is performing nicely. Bought a Keisaburo (Uchihashi san) plane a few weeks ago, and am very impressed. A bit pricey, but well made in every way. I think this younger smith has a bright future.

Stan

[David Weaver]

Everyone makes this mistake. From your picture, clearly the problem is improper support.

The important thing to keep in mind is that the purpose of the hammer strikes is not to bend the blade, but rather to deform the jigane (softer, low carbon steel layer). Each individual hammer strike deforms a little area of the jigane. This accumulated deformation causes the jigane to expand. But the high-carbon steel layer refuses to deform and expand, and the resulting stresses cause the blade to curve.

But to effectively deform the jigane without cracking the HC steel layer, the blade must be supported on your rounded metal anvil surface and aligned PRECISELY where the hammer would strike if the blade was not there. This is absolutely critical. The commercial jig shown in the previous post ensures this precise alignment. Remember, you don't want to support the blade across its width on the anvil, but only where the hammer blow will fall. Some practice is helpful.

Make a hardwood practice piece approximately the same dimensions as your plane blade, and cut a bevel as well. Hold it lightly between thumb and forefinger, and rest it against the anvil indexing against your forefinger just where you intend to strike. If you are supporting the blade on the rounded anvil surface properly, the hammer strike will not cause the wood to flip, or twist, or dance a jig, but it will just sit there while all the hammer's force goes directly through the wood, crushes some fibers on its way, and then flows into the anvil. It's a very stable feeling.

I don't have time to talk about the strike pattern, other than to say most of your strikes should be on the center two thirds of the bevel, and well away from the HC steel cutting edge. Strike with the bottom edge of the hammer making little crescent indentations.

Use a rounded metal anvil surface. The corner of a vise rounded over with a file works well, but I have used a 5lb sledge as an anvil in a pinch. A bit of paper glued to the anvil makes for a softer surface that might help your control. Use a lightweight hammer: A tack hammer, or sawset hammer works well. Don't try to develop a rhythm yet: Make every strike precisely and deliberately, pausing between strikes. Speed will come with lots of practice.

I hope this helps.

Stan

Excellent and precise as usual, Stan. It's such a joy to read your posts.

Glad to hear your mosaku is settling down. I'm sure mine will, though back when I was accumulating japanese planes, I wish you'd have been around on the forums as I'd have half as many planes and they'd be twice as good.

[Chris Griggs]

Excellent and precise as usual, Stan. It's such a joy to read your posts.

Indeed!

Stan!!!! My man! Where you been dude? We've missed you!

[Stanley Covington]

Indeed!

Stan!!!! My man! Where you been dude? We've missed you!

Dude! Busy as a one-armed, one-legged, hung-over, paper hanger! Come to Kyoto, and I'll show you!

[Chris Griggs]

Dude! Busy as a one-armed, one-legged, hung-over, paper hanger! Come to Kyoto, and I'll show you!

That's pretty darn busy! Always glad to have you pop up though.