A chuck for gripping a workpiece during a rotary operation includes a chuck body with a master jaw movably mounted on the chuck body. The master jaw includes a bayonet type locking structure. The master jaw also includes a face with at least one pin reciprocally mounted in and extending perpendicularly from the face. The pin is mechanically coupled to a piston reciprocally mounted in a piston chamber in the master jaw. The piston chamber is in communication with a source of pressurized fluid. The pin is reciprocated by selected communication of pressurized fluid to the piston chamber. A quick-change top jaw is also provided that may be quickly attached to and removed from the master jaw. The top jaw includes a bayonet type locking structure complementary to the bayonet type locking structure on the master jaw. The top jaw also includes an insert for capturing the pin in the master jaw. The top jaw is secured to the master jaw by placing the top jaw on the master jaw and aligning the bayonet locking structures. Pressurized fluid is then introduced into the piston chamber to withdraw the piston and pin. The top jaw is then rotated 90 DEG locking the bayonet type locking structures. Pressurized fluid is then removed from the piston chamber releasing the pin which seats in the insert in the top jaw preventing rotational movement of the top jaw.
