Patent ID: 8448544

Claim:
A method of manufacturing a utility knife blade comprising: heating and quenching a coil of strip steel material to harden the strip steel material and to form a martensitic microstructure substantially throughout the coil of strip steel material, the coil of strip steel material comprising a cutting edge portion along one edge and a remaining portion; tempering the hardened strip steel material by reheating the hardened strip steel material to form a tempered martensitic microstructure substantially throughout the coil strip steel material having a first hardness; and subsequent to said tempering, re-hardening the strip steel material locally at the cutting edge portion by reheating and quenching the strip steel material locally at said cutting edge portion such that the microstructure of the strip steel material substantially throughout said cutting edge portion is untempered martensite having a second hardness that is greater than the first hardness, while the tempered martensite microstructure having the first hardness remains the microstructure substantially throughout the remaining portion.