| 摘要 |
PURPOSE:To bore an upward enlarged hole section by inserting a rotational vibration type boring device body with a shank into the straight hole bored in a concrete body beforehand and performing boring with a stop sleeve lower end abutted to a concrete surface. CONSTITUTION:A shank 2 is attached to a rotational vibration type boring device and the lower end side of the device body 3 is inserted into the straight hole A formed in a concrete body beforehand. And the boring device is driven with the lower end face of a stop sleeve 12 abutted to a concrete surface B and kept to a fixed position, and vertically moved rotating a cylindrical body 1. The end section of a cutter body 9 is rotated being put out from the inside of the container hole 7 of the lower end of the body 3 and into the side of the cylindrical body 1 in this state. Since thus an upward enlarged hole section C is formed on the hole wall in the depth of the straight hole A, the drawing strength of anchor bolts against solidified concrete can be substantially improved.
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