a clamping or chucking apparatus for a shaper cutter for a gear shaping machine , especially a generating shaping machine for fabricating gears , containing an axially to - and - fro movable ram spindle and a shaper cutter holder affixed at one end of the ram spindle and having a contact surface for the shaper cutter . a centering projection protrudes axially away from the contact surface and serves for mounting the shaper cutter . a clamping plate is attached at the end of the centering projection over a clamping mandrel or plug . the coaction of the clamping plate and clamping mandrel serves to clamp the shaper cutter against the contact surface of the shaper cutter holder . the ram spindle is hollow and contains a spring arrangement and a piston . the spring arrangement is prestressed in order to exert an axial clamping force and is operatively connected by a coupling with the shaper cutter holder or shaper cutter . the coupling is constructed to transmit the clamping force and can be easily released after elimination of such clamping force . the piston limits within the ram spindle a cylinder chamber which can be connected to a pressurized medium source and eliminates the clamping force of the spring arrangement when the cylinder chamber is pressurized .