| 摘要 |
PROBLEM TO BE SOLVED: To provide a double pipe type drilling tool capable of preventing the damage of a connection section caused by striking force and reducing the impact force, vibration, and noise at a strike even when a polyvinyl chloride pipe or a thin steel pipe is used for an outer pipe. SOLUTION: A drilling means is provided at the tip of inner/outer double pipes, and drilling is made by the rotating force and striking force of an inner pipe in this double pipe type drilling tool. A cushioning member is arranged between the striking face of a striking member provided at the tip of the inner pipe and a strike receiving face on the outer pipe. The tip section of the inner pipe and an inner bit are connected by a joint member in this drilling means arranged at the tip of the inner pipe, the striking member is arranged between the inner bit and the joint member, and the cushioning member is arranged between the striking member and the inner bit or between the striking member and the joint member.
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