Abstract: A tool holder, which has a tool bit pivotal in a recess in one end thereof, extends coaxially through a generally bell shaped piston housing, and through the center of a piston slidably mounted on the holder for limited reciprocation in the housing axially thereof. The piston is urged by a compressing spring to a retracted position against one end of the housing, and has a reduced diameter annular wall that projects coaxially toward the end of the holder containing the tool bit. A tool actuating rod, which is pivotal in an axial bore in the holder, has on one end a lever which extends slidably into an axially extending helical slot formed in the annular piston wall, and is connected at its opposite end to the tool bit. When the piston is in its retracted position, the helical slot in its annular wall causes the actuating rod to swing the tool bit to an inoperative position within the holder recess.