Patent ID: 8776382

Claim:
A cutting instrument including a blade core and a cutting blade portion, the cutting instrument comprising: a skin formed in at least part of the cutting blade portion inclusive of a blade edge tip; the skin comprising an electrode material or a reaction product of the electrode material, the electrode material having been molten by pulse discharges induced between the blade core and an electrode in a machining oil, having as the electrode one of a mold molded from powder of at least one of a metal, a compound of metal, and a ceramics, a heat-treated mold being the mold as heat-treated, and a solid body of Si; and a gradient composition metal formed between the blade core and the skin, with depths within a range of 5 μm to 30 μm, wherein the blade edge tip is formed into a fine serrated shape caused by a roughness of the skin, and wherein the roughness of the skin is set by a control with a product of a peak current and a pulse width, the product being further divided by a 0.7-th power of a no-load voltage in the pulse discharges.