- Klutch Cobalt Step Drill Bit Set - 3/16in. to 3/4in. Dia, 3-Pc. Set High-speed, heavy-duty steel with cobalt coating Professional quality 3/16-1/2in. dia., 6-step bit 1/4-3/4in. dia., 9-step bit 1/8-1/2in. dia., 13-step bit