A metallic rotary endpiece designed to cut a hole(s) or a circular section(s) of the skull vault (calvarium) to provide access to the interior for diagnostic/therapeutic purposes or for the removal of a bone flap for brain surgery. It is available in various configurations such as: 1) two coaxial drill shafts (one rotating inside the other with the inner drill shaft extending slightly beyond the outer cutter); or 2) a single trepan bur rotating a in protective sleeve, both having a drive shank that connects to a powered handpiece and a built-in clutch mechanism that disengages with penetration of the cutter through the skull. This is a reusable device.