Wednesday, February 08, 2006
Kanna blade setting and dai tuning
NOTE: I am now writing a skeleton about japanese blade and dai setting. Please come back in a while to read more details and look at pictures.
Most of the time the kanna you buy new will come unfinished at a certain degree. You may only need to scrap a little bit the blade bed to have the edge protruding from the mouth, but you may also have a more significant job to do.
I have had various experiences with dais.
- Some were nicely cut, and the dai was a pleasure to tune.
- In another one, the blade was just lose in the dai, even before I did anything.
- Another one had the blade slightly angled (the blade edge wasn't perpendicular with the length of the dai)
- Bed scrapping or adjusting
- Mouth opening, adjusting
- Pin adjusting (together with subblade adjusting)
I shall detail this operation in a near future, with the help of some pictures or sketches.
Once the blade sits correctly, another important task is to tune the plane's sole. Japanese planes have a kind of hilly sole, with only 2 or 3 contact strips with the wood. The pattern depends on the type of work to be performed by the plane: trying, smoothing, finishing will define the height of the hills and depth of the valleys as well as the number of contact strips.
Now... How to create the pattern?
There are different approaches, depending on your equipment. I'll start with what I think is the most efficient and visual, but I haven't been able to try it since it requires a flat metalic surface, such as a thicknesser top, where graphite could adhear. If you have a surface plate in graphite, this may work as well.
What you do is to rub some graphite on the table, then rub your plane a couple of time on the flat surface. Look at the sole, and you will see that all high spots are darkened by the graphite. Nice, isn't it? You then just need to scrap these high spots until you get one strip at the front of the plane, one just BEFORE the edge, and optionally one at the back of the plane.
The other method is to use a straight edge. Japanese make some in steel dedicated for the purpose, but you can make your own as well. Mr Toshio Odate describe the method in his excellent and well written book. I find this to require some practice, and I used it in conjunction with the following.
This is the third method, which makes use of a straight edge but requires first a preliminary flattening of the sole. For this I am using a flat glass plate, mine being rather long since I have some long dai planes to tune.
Glass plate, sandpaper and double sidedtape
All you need for kanna tuning: your plane, glass plate, straightedge and a scrapper plane (a simple card scrapper would do also).
Note that the glass plate is locked in place.
After tuning, and rubbing on the graphite.