Fig. 849.
When the jaws are applied within the work, as in [Fig. 849] (representing the jaws of the chuck within the bore of a ring or piece of work w), the jaws spring in the opposite direction as denoted by dotted lines c, c, and when the jaws are locked to the work the latter moves in the direction of d and away from the chuck face. It will be observed that there is no true surface to put the face of the work against in either case.
Fig. 850.
This is remedied in independent dog chucks by the construction shown in [Fig. 850], in which each jaw has a square a, fitting in the grooves of the chuck, and a nut and washer at b secure the jaw to the face of the chuck so that the lost motion due to wear of the parts may be taken up.
Fig. 851.