This part of ISO 3408 specifies the calculation schemes for static and dynamic load ratings, and operational life, in order to obtain comparable values for the design and use of ball screws. NOTE The calculations have been based primarily on publications by Prof. G. Lundberg and A. Palmgren Acta Politechnica, mech. Eng. series Vol. I, No. 3, Stockholm, Sweden. Part 7, 1947. This part of ISO 3408 is applicable under the following preconditions: — elastic deformation of ball and balltrack; — hardness of balltrack basically exceeds a minimum of HRC 58; — conformity frs and fr n > 0,5; — the quality of steel of which the ball screw is made is equivalent to that of ball bearing steel or similar steel alloys; — optimum lubrification is always provided.