a clamp effort intensifier that multiplies the manual effort used for clamping vise jaws onto a workpiece through the use of a cam that actuates the vise jaws together to provide adequate clamping forces while substantially reducing the manual effort necessary to achieve a safe clamp force . the effort intensifier acts to load the vise jaw through a heavy spring which deflects as the jaws are loaded . the amount of deflection can be used to indicate the clamping force exerted on the jaws . an interlock to the machine tool used will prevent operation of the tool until the clamp force exceeds a desired level .