For example, ball screws are up to three times more efficient than Acme screws. This lowers system power requirements and allows using smaller gears, clutches, and motors. Ball screws cost less than hydraulic or pneumatic systems, operate more quietly, and don't require pumps, hoses, fluids, or shop air. And although belt, cable, or chain drives are often less expensive than ball screws, they also are less precise and stretch as they wear, which leads to inaccurate positioning. They operate like conventional power screws but the rolling friction of bearing balls replaces sliding friction.
Ball screws consist of a screw, nut, and balls that operate similarly to bearing components.
The screw has a precision ground or rolled helical groove acting as the inner race. The nut has internal grooves that act as the outer race. Circuits of precision steel balls recirculate in the grooves between the screw and nut. Either the screw or nut turns while the other moves in a linear direction. This converts torque to thrust.