| 摘要 |
PROBLEM TO BE SOLVED: To easily and accurately determine an allowable load capacity at each position in the axial direction of a rotary shaft by setting, as an allowable load, a load when the maximum amount of displacement of the rotary shaft in a bearing becomes a specific ratio for the amount of gap between the bearing and the rotary shaft. SOLUTION: Tools of various kinds of lengths are fitted to a shaft end 82a of a spindle 82 and a bending moment operating on the spindle 82 differs even in tools with the same cutting force, so that an applicable load differs at each position in the axial direction of the spindle 82. Therefore, the size of the load when the maximum value Zmax of the amount of displacement (the total of the amount of deflection within bearing members 83 and 84 and the amount of displacement of the spindle 82 when it is assumed that the spindle 82 is a stiff body) from a specific position (the end face position of the bearing member 83) from the specific position of the spindle 82 within rear-side bearing members 83 and 84 becomes a specific ratio (for example, 1/4) for an amount of gap S1 between the bearing members 83 and 84 and the spindle 82 before being generated due to a load in a bending direction being applied to each position in the axial direction of the spindle 82 is set to an allowable load Wp to be applied at each position in the axial direction of the spindle 82.
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