| 摘要 |
PROBLEM TO BE SOLVED: To reduce anisotropy in the radial direction by making a thermal expansion coefficient difference in the radial direction of a grindstone core of a disc shape made of a metal material less than a specific value in all bearings. SOLUTION: A round material 10 is formed out of extruding ingot of a metal material (for example, titanium or titanium alloy) to be a grindstone core material. A disc shape grindstone core material 12 with its cut surface as an end surface S is formed by cutting this round material 10 sectionally on a surface orthogonal in the longitudinal direction. At this time, though anisotropy of its axial direction X and a radial direction X exists as the round material 10 even on the grindstone core material 12, it has a material characteristic equal in all directions (X1-X4) in the case when only the radial direction X is seen). Thereafter, a grindstone core is made by fabrication. In this manufacturing method, it is possible to reduce anisotropy in the radial direction so that a thermal expansion coefficient difference in the radial direction becomes less than 1×10-6/ deg.C. Consequently, chattering never occurs on a workpiece even when high speed grinding work is practiced.
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