There are three tool options to consider when drilling large-diameter holes in thick steel: twist drill bits, hole saws and annular cutters. 1. Twist drill bits. Especially in steel thicker than ...

such as this Hillman Tapper drill bit in a 3/16-inch diameter and 3½-inch length. (We chose that size to test because 3/16-inch is a fairly standard hole size for installing towel rods and toilet ...