Abstract: A cylindrical tool holder has at one end a shank section disposed to be chucked in the drive spindle of a drill press or the like, and has in its opposite end a recess in which a tool bit pivots between an operative position in which it projects radially outwardly from the recess, and in inoperative position within the recess. The bit is connected to one end of an operating rod which is pivotal in a slot in the holder, so that when the rod is swung to one limit position the tool bit is swung to its operative position, and vice versa. An actuating disc which is mounted on the holder for limited rotation relative thereto, is frictionally coupled adjacent its outer periphery with a flywheel which is rotatably mounted on the tool holder, whereby rotation may be transmitted by the holder through the flywheel and friction coupling to the actuating disc. The actuating disc has thereon two spaced pins.