The single-acting mechanical clamping screw of the MSP series are designed for the external clamping direction (shafts, rollers), while the double-acting mechanical clamping screw of the MSPD series are designed for the external and internal clamping direction (rings, bushes). For this purpose, the clamping spindles are equipped with a mechanical wedge clamping system as a force amplifier, the double-acting clamping spindles are additionally equipped with an automatic changeover system. This system enables very high clamping forces with simple manual operation and low actuation torques. The optimized design of the robust wedge mechanism ensures self-locking in every clamping position as well as a high degree of stiffness, resulting in maximum operational reliability.