Irwin Step Drill Bit: 2 Hole Sizes, 7/8 in to 1 1/8 in, 1/4 in Step Increments, Black Oxide Finish

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.