Abstract: It was assumed that the contact loads between the balls and the grooves only cause the overall axial deformation of grooves’ helical surfaces based on the deformation mechanism of ball screw nut pairs， and then the axial deformation of the contact points between the balls and the grooves corresponding to the groove centers was deduced. According to the Hertz contact theory and the geometric relationship of the local deformation between the balls and the grooves， a calculation model for contact load was established. The two-dimensional plane contact problem was handled by the proposed model， finite element model and existing model， and the accuracy and feasibility of the proposed model were verified by result comparison. Taking a ball screw as an example， the distribution of contact forces and contact angles between the balls and the grooves with the axial load was analyzed with the proposed model.

Key words: ball screw nut pair, load distribution, Hertz contact, finite element method, axial load