Abstract: The disclosure relates to an improved chuck force control and compensating means for rotary machine tools, such as lathe. The control is used with power-operated chucks and provides reliable and effective compensation for the effect of centrifugal force, which otherwise tends to reduce gripping force on the workpiece. The control includes a static adjust signal generator, for establishing the desired level of gripping force upon the workpiece, and a rotation speed responsive signal generator, for generating a signal which is a function of the square of the rotational speed. These two signals are combined and serve to actuate a servo valve to control hydraulic pressure delivered to the power operated chuck. Hydraulic pressure increases with increased rotational speed, in order to maintain chucking force at a constant level.