| 摘要 |
PROBLEM TO BE SOLVED: To provide a release stop diameter expansion section on a drilled hole fixing an anchor bolt or the like on a base rock or a concrete placed section with mortar. SOLUTION: This diameter partially expanding device is provided with a rotary tube 1 fixed with a fixed flange 2 having the rotation center axis at the lower end section, a support flange 5 arranged to face the fixed flange 2, and a pair of half-disk-like bit bodies 4, 4 rotatably provided between the support flange 5 and the fixed flange 2. The bit bodies 4, 4 are rotatably fitted to a pair of screw shafts 3, 3 fixed at the symmetric positions of the fixed flange 2 with respect to the rotation center axis with their linear face sections kept in contact with each other to support the support flange 5.
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