Irwin Step Drill Bit, High Speed Steel, 8 Hole Sizes, 1/8" Step Thickness, 9/16" - 1"

The shanks on these step drill bits have three flats that help prevent the bits from slipping in the drill chuck during drilling. These cone-shaped bits have steps of increasing diameter marked along their cutting head. As each bit is pushed into a piece of sheet metal or other thin material, each step on the bit widens the hole. The bits also have a self-starting split point that prevents the bits from moving, or walking, when starting to drill, which eliminates the need for using a center drill to create a starter hole before drilling.