Thread: Tapping out kanna blade

Steve,

I guess the reason why I go back and forth between tapping and quickly working the back is that the times I've cracked a blade it seemed to be after I got to the point that I thought, "I wonder if I should flip the blade over now," which was quickly followed by the blade cracking.

I was pretty excited when I learned about the Tokyo Kanna Makers Guild mark and realized that this plane had the same mark, but haven't been able to nail down the maker of this particular plane blade. There's a plane blade by Ishido that has exactly the same background pattern, but a different name/inscription than mine, but that's as close as I got.

Thanks for those links to your blogs and video Wilbur.

I mostly use Japanese chisels which, as you explain in your blog about hollows, are rarely in need of tapping out. And, not using my Japanese kannas very much has also meant that I haven't had to tap those out yet, but there will come a time when I will have to get up to speed on this and everyone's advice here will be very helpful when that time comes.

On rehabbing blades, a Tormek (as used by Wibur in his blog) is very nice for that, but if you don't have one already or cannot justify that cost for various other uses, a diamond or CBN wheel on your dry grinder is another (slightly) less expensive option. As a woodturner I am constantly sharpening tools and can say from experience that these wheels grind much cooler than other dry grinding wheels. I have even re-ground thin Japanese knife blades on mine without any risk of de-tempering. An option that might be of interest to some.

I've tapped out quite a few blades now without a crack. I held off for years until I got some good information and then had a go. I was amazed that it worked so well and was so controllable.
The one thing I needed to understand was that I wasn't trying to bend the steel over the edge of the anvil as I would if I were bending a hot piece of steel. Instead the idea was to have the anvil support the blade directly behind where the blade is struck. This way the softer steel is pushed sideways which in turn bends the harder steel. The same way a bi-metalic strip works. One half expands more than the other and the whole strip bends.
I have chamfered the edge of my anvil to create a small flat. I then start by tapping the the small flat directly, without the blade, and ensuring that the hammer is coming down perpendicular to the flat and that the hammer is consistently hitting that point. I then put the blade between the hammer and flat. I then make sure I continuing hitting in exactly the same spot at the same angle and simply move the blade around.

Hope this is clear and of help to someone.

Regards,
Garry