the vise screw and removing the actuator assembly the vise screw can be removed as well and replaced with a different type of screw for a different type of actuator or the vise screw can be replaced with a manually operated screw merely by putting a thrust bearing in the bore 51 and using a screw that has an end nut that threads onto the end of the vise screw and bears against the thrust bearing to carry axial tension loads in the screw back to the end wall 18 of the vise there is no alignment problem with the modules because of individual forces between a plurality of cylinders because the individual pistons act independently and merely act through a bearing connection or compression carrying connection to add the force provided by one piston to the next piston in series a three way valve 91 is used for control because the actuators are single acting and the valve will either provide pressure to the actuators or exhaust air from the actuators because of the modular design having a separate module for each individual piston cylinder assembly any piston cylinder assembly can be replaced if it becomes worn or damaged and others can be added on as previously stated the modular form can be used for any type of clamping device because it is very compact and even where limited space is available.