Abstract: The invention provides a method and apparatus for controlling the level of clamping pressure applied by a clamp to a load. A pump, whose output is controlled by a normally open valve, establishes an initial level of clamping pressure. Through the use of a number of controllable fluid discharge systems, this pressure is automatically increased in increments depending upon the resistance of the load to the clamping pressure exerted. In a preferred embodiment, the controllable fluid discharge systems include discharge cylinders that contain predetermined volumes of fluid dischargeable by free-floating pistons residing therein. The outputs of the discharge cylinders are controlled by pressure-responsive valves to produce the desired relationship between clamp pressure and load rigidity.