The book considers base problems taken place in feed- and ball-screws. A short historical background is done and main equations describing condition of common deformation into lead screws are presented. Common case of screw loading is discussed and equations for calculation of load distribution intensity are derived. Deformations into round-profiled screws are considered taken into account contact stresses and radial forces. Loads and torques into ball screws are discussed and equations for calculating torque distribution between ball rows are given.