Abstract: A pair of gripper jaws are pivotally mounted on a machine tool spindle within a central bore that opens into the toolholder socket on the outer end of the spindle. The gripper jaws have serrated outer ends that extend into the toolholder socket in position to engage a threaded opening in the inner end of a toolholder which is to be clamped in the toolholder socket. Cam surfaces on a drawbar which extends between the gripper jaws interact with cam follower surfaces on the gripper jaws to cause the gripper jaws to move radially outwardly to clamp the toolholder within the toolholder socket when the drawbar is moved axially away from the toolholder socket. The gripper jaws have axial play therein. The drawbar is spring biased axially away from the toolholder socket to clamp the toolholder in the toolholder socket and press the toolholder against the margins of the toolholder socket.