Abstract: A chuck includes a generally cylindrical body and a plurality of jaws moveably disposed with respect to the body in communication with the body's axial bore. A generally cylindrical sleeve is rotatably mounted about the body in operative communication with the jaws so rotation of the sleeve in a closing direction moves the jaws towards the axis of the axial bore and rotation of the sleeve in an opening direction moves the jaws away from the axis. A bearing has a first race adjacent the body, a second race adjacent the sleeve and at least one bearing element disposed between the first race and the second race. One of the first race and the second race defines a ratchet. The other of the first race and the second race defines a pawl biased toward the ratchet. The ratchet and the pawl are configured so that when the pawl engages the ratchet, the ratchet and pawl prevent the second race from rotating in the opening direction with respect to the first race.