| 摘要 |
PURPOSE:To previously prevent the damage of a disk due to the difference between thermal expansion coefficients of a spindle and spacer by forming a metallic spacer with materials having a range of + or -50X10<-7>/deg with respect to the thermal expansion coefficient of a spindle. CONSTITUTION:The materials for the metallic spacer 3 and the spindle 2 are selected so as to obtain the difference of a range of + or -50X10<-7>/deg in terms of the spacer and spindle. Assuming that the material for the spindle is carbon steel and its thermal expansion coefficient is 105-110X10<-7>/deg, and that the material for the metallic spacer is a soft steel S10C and its thermal expansion coefficient is 110X10<-7>/deg, the difference between them approximately comes to zero. Accordingly, even if a glass substrate or ceramic one, whose surface defect is less and whose magnetic film is easy-to-form, is used, the damage of the disk due to the difference of the thermal expansion coefficient between the spindle and spacer can be previously prevented.
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