| 摘要 |
PROBLEM TO BE SOLVED: To fix a bush to a central hole at a low cost while a rotary precision is improved in a rotary tool. SOLUTION: For the rotary tool, a thin walled cylindrical bush 20 wherein an axially central at least one part can be reduced in a diameter, is inserted into a central hole 12 of a cylindrical tool main body 11. The bush is secured to both end sides of the central hole of the tool main body by shrinkage fit, comes in liquid-tight contact with the central hole on both end sides of the tool main body, and annular space parts 24a and 25b are provided between the tool main body and the central hole in an axially intermediate part of the tool main body. By reducing a diameter of a thin wall part of the bush by pressurizing by enclosing a fluid into the annular space part in a state wherein a rotary shaft part in a state wherein a rotary shaft 31 is inserted into the central hole via the bush, the rotary tool is secured to the rotary shaft.
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