Powdered high-speed steel (HSS) differentiates this plane from almost all other Japanese planes. The HSS edge is bonded to a soft iron backing for use with the most difficult woods. This high-speed steel is a special formulation created by Hitachi Metals, and the skills that Tsunesaburo brings to the hardening process create nothing less than a “super” steel. Blades are extremely tough, which creates some difficulty in sharpening. To resolve this issue, Tsunesaburo modified the blade slightly to create a hollow behind the tip of the blade, so only a small area needs to be honed and flattened to keep the blade razor-sharp. The 50mm blade is housed at 40° in a Japanese White Oak body.