Abstract: A chuck with radially reciprocating jaws is disclosed wherein each jaw is supported on a jaw support member movable relative to a base. An actuator is axially disposed in the base for axial reciprocation, the actuator having pivotally connected first and second links which extend radially from the actuator to engage the jaw support member. An eccentric cam connects each of the links to the jaw support member so as to translate the axial motion of the actuator into radial motion of the jaw member. One of the eccentrics has a fixed defined axis with respect to the base, while the other eccentric is received in bushings which are axially slidable with respect to the base.