IRWIN Unibit 10239 Stepped Dill Bit Step Drill Bit, Hex Shank, 7/16 in Dia Shank                      High-speed steel bit with single flute cutting edge for greater control through steps. Hex shank prevents slipping in drill chuck. SpeedPoint tip penetrates faster and prevents walking in applications such as drilling holes into thin materials such as stainless steel, copper, brass, aluminum, plastic and laminates.