Blade setup with kanaban and silicon carbide grit
Posted: Sun Jun 04, 2017 2:42 pm
Hi all,
I've been quietly working on my kumihimo (Japanese braiding) stand designs and builds, and had a chance to take one of Dale Brotherton's workshops at the Port Townsend School of Woodworking last fall. Dale's workshop was very, very useful at my relatively beginner stage of Japanese hand tool use. My favorite takeaway was the technique for initial plane blade setup using a kanaban (steel lapping plate) and a dab of silicon carbide grit (200 grit). This process is used to flatten just the part of the ura near the edge. The silicon carbide grit is dampened; pick up some grit on a wet fingertip and spread a line down the length of the kanaban. Place the grit line so that, with the blade positioned as if for lapping on a stone, only the ura-edge is contacting the abrasive. The blade is then lapped until the grit just starts to dry up. At this point, we have some magic: the "high" spots on the back are filled in and blackened by broken-down silicon carbide, while the "low" spots in contact with the kanaban have a nice shine. This gives precise feedback which we take to anvil and use to tap out the high spots, bringing them closer to the desired plane. Now repeat by adding a dab more water and lapping the edge more. Once the ura-near-edge work is complete, lapping steps proceed on stones as usual.
The cycle of lap/check/tap out is very fast and really leaves no guesswork as to what's going on with the blade. It provides a similar desirable property to Chris' technique using UHMW film to lift and protect the "legs" of the ura, in that abrasive is never applied to the kanaban where the legs contact it. Dale, like Chris, also makes tapping out very accessible; I gather that this essential skill is not always known or well-taught.
Apologies for the scant description; I'll try to visually document this process when I next prep a blade.
I've been quietly working on my kumihimo (Japanese braiding) stand designs and builds, and had a chance to take one of Dale Brotherton's workshops at the Port Townsend School of Woodworking last fall. Dale's workshop was very, very useful at my relatively beginner stage of Japanese hand tool use. My favorite takeaway was the technique for initial plane blade setup using a kanaban (steel lapping plate) and a dab of silicon carbide grit (200 grit). This process is used to flatten just the part of the ura near the edge. The silicon carbide grit is dampened; pick up some grit on a wet fingertip and spread a line down the length of the kanaban. Place the grit line so that, with the blade positioned as if for lapping on a stone, only the ura-edge is contacting the abrasive. The blade is then lapped until the grit just starts to dry up. At this point, we have some magic: the "high" spots on the back are filled in and blackened by broken-down silicon carbide, while the "low" spots in contact with the kanaban have a nice shine. This gives precise feedback which we take to anvil and use to tap out the high spots, bringing them closer to the desired plane. Now repeat by adding a dab more water and lapping the edge more. Once the ura-near-edge work is complete, lapping steps proceed on stones as usual.
The cycle of lap/check/tap out is very fast and really leaves no guesswork as to what's going on with the blade. It provides a similar desirable property to Chris' technique using UHMW film to lift and protect the "legs" of the ura, in that abrasive is never applied to the kanaban where the legs contact it. Dale, like Chris, also makes tapping out very accessible; I gather that this essential skill is not always known or well-taught.
Apologies for the scant description; I'll try to visually document this process when I next prep a blade.