Abstract: An improved chuck for holding an object such as a tool or work piece. The chuck includes circumferentially spaced jaws for grasping an object and a gear mechanism for adjusting the radial position of the jaws to grasp object of varying size. The jaws of the chuck are movable radially outwardly to an open position to permit insertion of an object there between and are adapted to move radially inwardly to an object grasping position. The improvements in the chuck include inclined key threads on the jaws; a rotatable jaw positioning collar around the jaws, including inclined, inwardly extending, circumferentially spaced key threads adapted to cooperatively engage and disengage the key threads on the jaws; a member positioned around the collar for engaging and rotating the collar to engage and disengage the key threads; and, a spring for normally yieldably urging the jaws axially outwardly and radially inwardly when the key threads are disengaged.

Abstract: A chuck having self-closing jaws, and a key-threaded rotary ring to engage said jaws in working contact with a tool within their grasp or to disengage said jaws so as to permit their free movement. The jaws themselves are such that the act of performing work with a tool held by said jaws increases the holding pressure exerted by said jaws on said tool.