Craftsmen often create custom mameganna (small “bean” plane) for small wood projects requiring a custom radius or access to tight spaces. In this case a large post kanna was made from a section of industrial paper cutting blade as part of a timber framing project.
Materials for this large kanna are a scrap block of hardwood and a length of industrial paper cutting blade that has passed its usefulness. The wood is usually shiragashi, Japanese white oak, but some type of oak or similar wood that has been seasoned sufficiently should provide the strength and tension required for a kanna. Among the few remaining pieces of wood here, this block of unknown tropical hardwood was the closest candidate with about the right dimensions for the width of the blade.
The paper cutting blade has some good characteristics in that it is very hard 18% tungsten alloy steel inlaid into very soft iron or steel. Because it is hss, however, it cannot be heated and forged or the complex industrial temper will be lost. Therefore it was necessary to shape it entirely by grinding and filing, keeping it cool while working. It also has the drawback of being somewhat narrow and will not protrude very far above the dai.
To make the paper cutter blade into a kanna blade the profile was cut out (most of it can be sawn but the hagane must be snapped or cut with a grinder) and then a slight taper added from the spine to the beginning of the bevel. This kanna will be of the flat ura type for now and have no chip breaker, though it could be modified at a later time.
Tools used to plan and make the dai include a saw, drill, kanna, chisel, hammer, thin coarse file, protractor, and sashigane. The blade is 123mm (4 7/8″) wide, 10mm (~3/8″) thick at the spine, and the cutting edge is 112mm (~4 3/8″) wide. The dai is 263mm x 156mm (~10.25″ x 6″).