| 摘要 |
PURPOSE:To improve the accuracy of positioning of the center of a disc, by providing taper inscribed with a center opening of a hub to the center of a center table, and projecting a center boss freely rotatably and movably up and down. CONSTITUTION:A slope of a center boss 13 contacts the lower end of a center opening 3 of a hub 2. Since a chamfering angle of a chamfering section 19 is generally 45 deg., an angle theta taking a plane of the center table 6 of the slope of the center boss 13 as a reference is set at 45 deg.<theta<90 deg., then the center boss 13 moves up and down even if the circular diameter of the opening 3 is dispersed to inscribe the slope of the center boss 13 with the opening 3, allowing to align the disc 1 to the center. The accuracy of disc centering is entirely independent of the processing accuracy of the opening 3, and dependent on the slope of the center boss 13 and the coaxial accuracy of a sleeve 14. |
