A workpiece chuck has a plurality of support blocks adapted to be mounted on the front face of the chuck body in circumferentially spaced relation and at various locations spaced radially different distances from the central axis of the chuck. Within each support block a jaw rod is arranged for sliding movement along an axis inclined at an acute angle to the central axis of the chuck. A coupling interconnects the inner end of each jaw rod with an axially displaceable puller plate within the chuck body. The front plate of the chuck and the puller plate are formed with registering, radially elongated openings to permit radial adjustment of the jaw rods and to enable them to be retracted outwardly from the chuck body together with their support blocks.
