PURPOSE: To reduce the size of the whole of a device and to facilitate regulation of a gap between bearings and regulation of a pre-load by a method wherein two or more track surfaces are formed to a stud, and the axes of the adjoining track surfaces are positioned eccentrically to each other.

CONSTITUTION: First and second track surfaces 1a and 1b are formed to a columnar stud 1. The axes of the first and second track surfaces 1a and 1b are positioned eccentrically to each other by a distance of . A number of rollers 6 are arranged circumferentially of the track surfaces 1a and 1b, and outer wheels 3 and 4 are engaged with each other through the rollers 6. A gap between a slide bed 12 and a track bed 10 is regulated by changing an eccentric amount through slight rotation of a mounting screw part 1c of the stud 1. This constitution reduces the size of the whole of a device, and enables facilitation of regulation of a gap between bearings and regulation of a pre-load.