This self-feed bit extension is used with self-feed wood bits that are used for drilling large diameter holes in wood for pipe, conduit and other applications. The replaceable coarse screw point drills quickly in dry, wet, and gummy wood. All bits have a 7/16 in. hex quick change impact shank that fits 1/2 in. or larger electric drills or 7/16 in. hex impact wrench drills.