BALL SCREW NUT, LINEAR GUIDE DEVICE USING IT, BALL SCREW FOR STEERING, AND MANUFACTURE OF BALL SCREW NUT

摘要

PROBLEM TO BE SOLVED: To provide a ball screw nut and its manufacturing method whereby it is practicable to form a ball screw having a ball running groove of small diameter and large lead, lessen the surface roughness of the groove, and generate an accurate R-shape of groove. SOLUTION: A ball running groove 1c is formed by a rolling process at the internal circumferential surface of a ball screw nut 1. Because of this groove formation process not by grinding but by rolling, even a ball screw nut 1 of a small diameter and large lead can be manufactured. The surface of the groove 1c is processed into a flat surface with no unevenness provided owing to the plasticity processing during the rolling, which offers a specular finish surface, whereby the surface roughness is decreased. The rolling is executed with a rolling tap which involves less wear and excellent durability, and an accurate R-shape of groove is obtained.