Ball screws offer higher efficiency than lead screws because ball screws use rolling friction and lead screws use sliding friction. Ball screws require lower torque to move the same load as lead screws. Ball screws normally have higher load ratings than lead screws because ball screws have hardened steel ball bearings running in hardened steel screw threads and nut threads. Lead screws are often made of steel but not hardened steel. The nuts of lead screws are often made of a polymer or a soft metal such as bronze. Share and save: Ball screws offer more precise positioning than lead screws. Lead screws must have some clearance between the screw threads and nut threads. Ball screws can have carefully controlled clearances between the threads and the ball bearings, or even preloaded threads and ball bearings. Ball screws can operate at higher rotational speeds than lead screws. The sliding friction between a lead screw and its nut causes heat. Lead screw operation must not exceed a speed and loading where friction heat is generated faster than the heat can be dissipated or else the nut material will deteriorate.