Core Drills are used for enlarging holes that have already been punched or drilled in normal steels, cast iron and a variety of ferrous and non-ferrous alloys and metals. The multi-flute design cannot drill the initial hole, but can significantly widen an existing hole and provide a smooth finish. Taper shank core drills are used in a taper socket spindle. Straight shank core drills are used in a chuck or collet, and are sized proportionally to the drill diameter. These core drills are twist drills and quite different from the hollow-type core drills used to produce geological core samples. For optimal results, use coolant as recommended.