a tool turret has a hydraulically slidable interlocking or clamping member in alignment with the rotary axis of the turret head for interlocking or clamping the turret head to the housing and for charging the turret head with an axially reactive force by hydraulic pressure working on the interlocking or clamping member . the axially reactive force counters the axial force exerted by the interlocking or clamping member on the turret head . a hydraulically slidable piston slides relative to the housing and exerts on the turret head in its interlocked or clamped state a force applied in the same direction as the reactive force .