Abstract: A holding device having a flexible diaphragm, a central pin embedded in the flexible diaphragm, a pressure ring in contact with a periphery of the diaphragm and a mechanism for lifting the central pin with respect to the pressure ring. The diaphragm has a plurality of cams circumferentially disposed about the diaphragm. An inside surface of a wall of the pressure ring has recesses which mate with the cams and connect the diaphragm with the pressure ring thereby securing the diaphragm against relative rotation with respect to the pressure ring and allowing the diaphragm to move axially with respect to the pressure ring.