| 摘要 |
PURPOSE:To prevent off track by fitting housings made of materials having almost the same linear expansion coefficient as that of a bearing in the clearance between a base cover and the bearing. CONSTITUTION:The upper and lower housings 8' and 9' are fitted to a base 1 and a cover 2 on clearance fitting basis with screws 21 and 22 arranged at equal distance and an equal angle to a spindle center 23. Consequently, deviation between the base 1 and cover 2 of aluminum materials due to a temperature rise is absorbed by screw parts of the fitting screws 21 and 22. Therefore, the variation rates of internal diameters of the housings 8' and 9' are not affected by the thermal expansion of the base 1 and cover 2 and there is not gap formed between the internal diameters of the housings 8' and 9' and the external diameters of upper and lower bearings 5 and 6, so that the coaxial degree between the upper and lower bearings 5 and 6, i.e. perpendicularity of a spindle is not spoiled. |
