To provide a ball screw capable of reducing slide friction loss per unit time on a screw shaft side and prolonging service life of durability.
When arithmetic average surface roughness of a channel face 14a in an inner side track channel 14 is Ra (s), arithmetic average surface roughness of a channel face 15a in an outer side track channel 15 is Ra (n), a ratio of radius of curvature of the channel face 14a in the inner side track channel 14 to ball diameter is Rs, and a ratio of radius of curvature of the channel face 15a in the outer side track channel 15 to ball diameter is Rn, arithmetic average surface roughness of the channel face 14a in the inner side track channel 14 is Ra (s) = 0.8 to 1.25 Ra (n), and a ratio of radius of curvature of the channel face 14a in the inner side track channel 14 to ball diameter is Rs = 1.015 to 1.05 Rn.
OKITA SHIGERU
Yoshiaki Naito
Cui Shu Tetsu