Patent ID: 8550442

Claim:
A workpiece holding device comprising: a substantially spherical ball with means operable for releasably retaining a workpiece; a socket mountable on a worktable, the socket comprising an external screw thread; means for mounting the socket on the worktable; a ball-receiving element moveably mounted within the socket and being shaped to provide a first ball-receiving surface; and ball clamping means for releasably clamping the substantially spherical ball against the first ball-receiving surface with a ball clamping force, the ball clamping means comprising:— an external member for transmitting the ball clamping force to the socket, the external member comprising an internal screw thread; and an internal member including a second ball-receiving surface for contacting and for clamping the substantially spherical ball between the first and second ball-receiving surfaces; the workpiece holding device being characterized in the ball-receiving element is moveable along at least one axis within the socket in a plane substantially perpendicular to the ball clamping force; and in the external screw thread of the socket and the internal screw thread of the external member cooperate for connecting the external member and the socket and for generating the ball clamping force by tightening the connection between them.