Abstract: A keyless chuck (10; 301) comprises a jaw housing (28; 303) with jaws (32; 333, 335, 337 ) which are slidably mounted in guideways (40; 319, 321, 323) between a rearward opened position and a forward closed position. A jaw thrust member (34; 345) is coupled to the jaws and is slidably mounted in the jaw housing to apply a thrust force to the jaws and to maintain the jaws in the same relative axial location. A nut (42; 355) is fixed to the jaw housing and has a threaded opening (46; 357) coaxial with the chuck axis (A.sub.x). A threaded spindle (48; 305) is engaged in the nut opening and is movable forwardly to apply clamping force to the jaws and rearwardly to remove clamping force. The spindle preferably engages the jaw thrust member through a small area contact patch (72; 401) to limit operating friction.

Abstract: A keyless chuck includes a jaw housing with jaws that are advanced in respective guideways to grip a tool bit and retracted to loosen the grip on the tool bit. A jaw thrust member is coupled to the jaws and to a threaded spindle and is forced forwardly or rearwardly to advance or retract the jaws. The threaded chuck spindle engages the jaw thrust member through a small-area contact patch to limit the operating friction and thus provide a chuck which can be readily hand-tightened and which self-tightens in response to torque transmitted through the chuck. A lock mechanism is provided to selectively lock a chuck adjusting sleeve relative to the jaw housing to allow uni-directional movement of the chuck adjusting sleeve relative to the jaw housing or selective bi-directional locking of the chuck adjusting sleeve relative to the jaw housing.