Abstract: An expansible shaft in which a screw that is rotationally and axially movable relative to the housing is rotatably connected to the operating rod so that clockwise screw rotation moves the rod axially in one direction and counterclockwise screw rotation moves the rod axially in the opposite direction.

Abstract: An expansible shaft in which an axially-movable cam forces a core engager radially outward into engagement with a surrounding core. A cam follower attached to the core engager slidingly engages a cam surface of the cam, a recessed slot is parallel to the cam surface, and one end of a cross-bore in the cam follower overlies and follows the slot as the cam follower slides along the cam surface. A second bore perpendicularly intersects the cross-bore. A first member is mounted in and forms a slip-fit with the cross-bore, a second member is mounted in the second bore, and the length of the first member is such that a portion of it projects into the slot when the second member is within the bore intersection, but the entire first member fits within the cross-bore when the second member is withdrawn from the bore intersection.