HRC of HSS 6542 (W6Mo5Cr4V2)is 67~70. It is ideally designed for high production machine works in low and medium carbon steel, as well as non-ferrous material like aluminum, brass, bronze, and copper. And HSS 6542 has a good red-hardness and retains its cutting edge sharpness longer than other general purpose high speed steel. Its HRC retain 63~65 when the temperature reach 1112 F. HSS 6542 which has a melting point of 4724.6~4748 F. These bits will drill through the toughest steel like truck frames, stainless steel, farm implements, and more, very durable.