| 摘要 |
A shaft member for a fluid dynamic bearing device that has a recess to cause a dynamic pressure effect of a fluid in a bearing clearance, which is formed on it by rolling, and where a surface layer portion of the recess and a surface layer portion of a surrounding region of the recess has a nitride layer, and where nitrogen is diffused and penetrated in a material of the shaft member that is formed by nitriding after the rolling.
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