Abstract: Supporting clamps for a tool such as, for example, a pile driver machine are used to tilt a machine support relative to a horizontal plane. The clamps include a pair of jaw elements one of which is received on a pivot and the other of which has a pair of parallel spaced pistons. The clamp jaw elements gird a fixed reference device to support the tool securely for subsequent operations. Different pressures applied to the two pistons causes the clamp to tilt about the fixed reference device, and thereby to tilt the tool to which it is attached. The difference in pressure is controlled to rotate the tool as desired. In a second embodiment of the invention, the desired angle is established by controlling an angle of a backup surface, and applying equal pressure to the two pistons. The fixed reference device is driven into the angled backup surface to establish the desired tilt angle. In a further embodiment, one piston is disposed at each side of the gap. The two pistons are spaced apart along the gap.