The Titanium Nitride Coated Drill Bit Set 17pc features 17 titanium nitride-coated high-speed steel drill bits. The titanium nitride coating is tough and very smooth to reduce friction and heat build-up extending the bit's service life to six times more than regular high-speed steel drill bits. Use them for repetitive drilling in most ferrous and nonferrous metals, plastic and wood. Not recommended for use in aluminum or hard metals such as stainless steel. For a sure grip, all sizes 3/16" (4.76 mm) in diameter and larger have three flats on the bit's shank. Their 135 degree split-point tip on all bits 1/8" (3 mm) in diameter and larger eliminates the need for a center punch and keeps the drill from "walking" on hard surfaces.