Measuring the clamping forces on cylindrical workpieces is a key factor in the geometrical tolerances of such components, especially if they are slender as the case of thin rings. The lower the clamping force, better tolerances will be achieved, but with the disadvantage of reducing friction and, therefore, increasing the risk of slipping. Therefore, achieving a minimum but safe clamping force is a key factor to control the process. Usually, these parts are made in lathes that have concentric plate clutches and these are fixed mechanically by wrenches or hydraulically through the control of pressure by valves. A simple and economic method is proposed to measure the clamping forces in lathes, although it is necessary the use of a model for the ring deformation. This method allows knowing the clamping force from the torque applied by a dynamometric wrench, or from the hydraulic pressure controlled by valves.