Blade setup with kanaban and silicon carbide grit

John Whitley
Deshi
Location: Seattle, WA
Posts: 148
Joined: Sun May 04, 2014 8:56 pm

Blade setup with kanaban and silicon carbide grit

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.
djwong
Deshi
Location: Cupertino, CA
Posts: 134
Joined: Wed Feb 01, 2012 12:52 pm

Re: Blade setup with kanaban and silicon carbide grit

Sun Jun 04, 2017 5:50 pm

Hi John,

I have used silicon carbide grit and a kanaban to setup the backs of blades in the past. I gave up on the process because of the mess. The black grit would obscure the back, forcing me to constantly wash the grit off to gauge progress. Perhaps I was using too much grit compare to the process you are describing. I am interested in learning more about how the grit blackens the low spots as feedback. Looking forward to your photos.

Last summer I was interested in signing up for Dale's class when it was announced he was injured in a fall. I just checked and it looks like I missed his most recent class.
John Whitley
Deshi
Location: Seattle, WA
Posts: 148
Joined: Sun May 04, 2014 8:56 pm

Re: Blade setup with kanaban and silicon carbide grit

Sun Jun 04, 2017 10:40 pm

@djwong, thanks for the feedback. I'll try to make that part clear. The amount of grit used at one time is very small. Wet a finger, dip the end of that finger in a small container of grit(**), and spread that on the kanaban. This initial application is probably not be enough for the entire flattening, so reapply sparingly as needed. There was a little mess, but not that much in the scheme of normal lapping and sharpening with stones.

(**) I use a film canister for my working supply. I bought a modest amount (maybe ~1lb) for cheap (~$5, iirc), enough to last decades.
djwong
Deshi
Location: Cupertino, CA
Posts: 134
Joined: Wed Feb 01, 2012 12:52 pm

Re: Blade setup with kanaban and silicon carbide grit

Mon Jun 05, 2017 1:10 am

I remembered I once made a photo album for someone that was curious about the process. I did not have a japanese blade to use, so I used a new Stanley 750 chisel as the test subject. I was using a stick with an embedded magnet to hold the blade and apply pressure.

kanaban album

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