Carving tools belonging to Mr. Ito Susumu (entry by David Bull)
Also known as the 'ko-gatana' (small sword), this knife is one of the tools that was given to me by Mr. Ito's widow a few months after he passed away in late 1998. It appears here in these photos exactly as it was when he laid it aside for the last time; I have not sharpened it or altered it in any way.
The handle is a dark hardwood, perhaps 'keyaki', and the ferrule is brass. The blade is a typical two-part steel laminate, laid into a slot cut into the spine of the handle.
Just barely visible in the photo above, is the slight curvature that Ito-san put into the shape of the blade (tweaking it with a pair of pliers). Doing this ensured that when he rubbed the back side of the blade on the finishing stone, the action of the stone was concentrated right at the absolute tip of the blade, thus avoiding any 'rounding' of the tip.
This view underneath the ferrule shows a tiny wedge of wood driven in to hold the blade firmly. Ito-san liked using the thinnest blades he could get, and they were sometimes thus loose in the slot ...
Thin as this blade is (a hair under 1mm thick), he used a file to make it even thinner in the area near the tip, explaining to me one day that this saved a lot of time when sharpening. This section is irregular, but runs about 0.7 mm in thickness.
The sharpened 'bevel' area is not completely flat; it runs off from the filed area in a shallow curve, before dropping off in a sharper curve to the blade edge itself.
The back surface of the blade is mirror smooth; an area of the ferrule has been worn away through contact with the stone during final sharpening ...
... as has an area on the top surface. Interestingly enough, the angle of this worn away portion on the top side does not match the angle on the blade itself. But if one imagines the blade becoming shorter and shorter as it is repeatedly sharpened, it comes to match the angle of wear on the ferrule when it is about a full centimetre shorter than it is at present - indicating the point where Ito-san must have then temporarily removed the little wedge, and pulled the blade 'out' to use the next portion ...