US Patent 7374178 Workpiece holder

A workholding apparatus including a body and a drive member carried by the body, so that the drive member and body partially define a fluid chamber therebetween for containing a fluid. The drive member includes an annular flange that axially abuts and that attaches to the body to resist torsional twisting of the drive member relative to the body. A driven member is also carried by the body and includes multiple displacement reliefs therein. Interengagement features are provided between the driven member and other components of the workholding apparatus, such as the drive member, to resist torsional twisting of the driven member.