Chapter II
The Knife
San Mai, Aogami #2, octagonal walnut.
Construction
San Mai means three layers. A hard steel core is forge-welded between two softer outer layers of iron. The hard core gives the edge; the soft cladding protects the brittle centre and absorbs shock from the board. The visible line where they meet — a soft, wandering shadow along the flat of the blade — is the only ornament the knife has.
The Core
Aogami #2, blue steel, made by Hitachi at the Yasugi works. It contains tungsten and chromium in carefully held quantities. It rusts. It is worth the trouble. No stainless steel sharpens to the same edge or holds it for the same length of time. You will learn to wipe it. The knife will repay you in every onion for thirty years.
The Geometry
210mm edge. Tall enough at the heel (47mm) for knuckle clearance. Distal taper from spine to tip, finished by hand on a water wheel. The edge is set at fifteen degrees per side and finished on a 6000-grit natural stone. It will arrive sharp enough to part a tomato by its own weight.
The Handle
Octagonal, turned from a single piece of American walnut, fitted with a buffalo horn ferrule. The octagon is traditional — it locates itself in your hand without you thinking about it. There is no rivet, no hidden tang screw, no plastic. The blade is friction-fit and pinned with bamboo. In time the wood darkens. This is correct.
- Edge length
- 210 mm
- Heel height
- 47 mm
- Spine thickness
- 2.8 mm at heel, 0.4 mm at tip
- Total weight
- 168 g
- Hardness
- HRC 63 ± 1
- Edge angle
- 15° per side