Differentially tempered or through hardened?
Traditional Japanese swords are differentially tempered to make the edge hard and the spine soft. This process creates a temper pattern (hamon) and is responsible for most of the curvature of the blade. The trouble with steel is that you often need to give up something to get something. The advantage of differential tempering is the ability to have a hard edge (mostly martensite) so it will stay sharp and a soft spine (pearlite, cementite, ferrite) so it will absorb impact. A through hardened blade will compromise on durability vs. hardness. All our blades are tested to be both tough and resiliant with the correct balance of properties. Again, it is difficult to say if one method is much better than the other. Q: How does a bo-hi (groove) affect the blade? A: This question has come under debate recently, however we believe a blade groove works like an I-beam, giving lightness with only a minimal sacrifice of strength. It also produces some drag causing a “swoosh” as the blade swings ca
