Thread: kanna blade chipping

There's mention of this in Odate's book - the solution given there is to leave the blade on a hot tin roof in order to temper the steel a bit more. However, if it's an old blade, I'd imagine that it's been ground well past any the brittle section caused by the initial heat treating.

You could try popping it in the oven at around 100-150 degrees C for a few hours and see if that helps matters.

How did you grind the bevel? Leonard Lee's sharpening book mentions that heat produced by dry grinding will negatively affect the high carbon steel in japanese blades by forming microscopic cracks that will chip at the edge. Also, too narrow a bevel angle can make for a weak edge that will be prone to chipping depending on the hardness of your wood. After only a little testing I see good reason to stick close to the 29-30deg bevel that's recommended for a standard 40deg dai.

The bevel is 30 degrees, but the grinding could be part of the problem- I did grind it dry, but I didn't let it noticeably hot.

Howard,

I had the same problem with a blade I bought some time back. I reckoned the blade had not been tempered back enough so I put it in the kitched oven at about 180 degrees C for a about half an hour. It stopped it from chipping and the blade works well now. If you try this, be very careful not to over heat it.
Toshio Odate has a story in his book about asking the Kanna shop owner how to stop a blade from chipping. His answer was to put the blade on the roof of his house for some time. This would also very mildly temper the blade and soften it slightly.

Regards,
Gadge

NZStu,

I didn't see your post before I posted mine above and now realize I virtually said exactly the same as you. Sorry.

Regards,
Gadge

Originally Posted by Gadge

NZStu,

I didn't see your post before I posted mine above and now realize I virtually said exactly the same as you. Sorry.

Regards,
Gadge

Great minds and all that...