Plug Bit

A boring tool with a double twist body which may be either of one diameter, or may be back-tapered from the cutting edges. When of one diameter, it may have either a plain cylindrical pilot or a truncated screw point. When back-tapered, it may have a common screw point, a truncated screw point, or a plain cylindrical pilot. Excludes counterbore (as modified); and countersink. See also bit, auger.