<p>The clamping apparatus has a hydraulic supply connectable piston (5) that is arranged in extension of the housing (1). An exhausting support tube (2) is arranged in the housing of working clamping forces on an underlay (B). A train nut (10) is fastened by threaded engagement on a screw thread end section (A) of threaded bolt that is supported in longitudinal direction with a pressure surface (9) against a pressure transmission surface (6). The piston is acted toward a housing-side spring support and a piston-side spring support upon a return spring.</p>
