Designed for drilling hardened steels in the range of 45-65 RC. Carbide tipped drill bit with uncoated bright finish. Run die drills at 75 to 100 surface feet per minute with steady hand feed. It is a good practice to clear the drill from the hole to allow coolant to wash away the chips. Sizes under 11/64 are solid carbide spade construction.. Round shank for use in a wide range of tool holding systems