HSS core drills features for enlarging existing punched or drilled holes, work well in normal steel, castiron, and other ferrous and non-ferrous metals and alloys[...]

features: single cutting edge creates perfectly round holes in metal. plastic . wood and other thin materials without center punching. tin-coated/uncoated optional 20 models available providing a rang of holes from 1/8" to 1-3/8"(4MM to 35MM)[...]