Step Drills are High Speed Steel combination cutting tools with a tapered end designed to produce clearance holes in a single pass for cap screws or for taps. The through hole style drills holes for cap screws sized between #6 and 1/2". The tapped hole type drills 45 degree chamfered holes with the diameter needed for tapping the holes to approximately 70% thread. Both types also produce a counterbored area correctly sized for the screw head. Irwin Unibit drills are also sometimes referred to as step drills, due to their tapered stair-step conical geometry. Irwin step drills are designed to machine a large number of different hole diameters with a single tool.