| 摘要 |
PROBLEM TO BE SOLVED: To simply form a hole with the smooth bottom on the road surface within a short time. SOLUTION: A cutting bit 1 having a bit 3 making the bottom and circumferential surface as the cutting surface is connected and fixed to a rotational shaft of a perforator revolving the rotational shaft with an axis X2 of a revolving shaft. The axis X2 of the revolving shaft for the perforator is positioned to a bit mark indicating the center position of a hole H formed in the road surface R in advance. The cutting bit 1 is rotatated by rotating the rotational shaft, at the same time, while revolving the rotational shaft with the axis X2 of the revolving shaft as the center, the cutting bit 1 is gradually lowered, and the road surface R is spirally cut up to a specific depth by the bit 3 of the cutting bit 1 to form the hole H.
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