These highly accurate, self-centering hinge drilling hinge bits are used for precise drilling of holes for cabinet and door hinges, door butts, striker plates, window pulls and all large and small hardware. Desired depth is achieved by loosening a setscrew, setting the high speed drill bit, and then tightening the setscrew. Bit is Self-centering & accurate. Body has screw top for ease of cleaning & changing bit. Replaceable bits. Bodies are stamped with size. The spring loaded outer guide keeps drill centered for perfect pilot holes. Top unscrews for easy cleaning.