| 摘要 |
Rock bolts, which are inserted into the rock walls of mines for various utilitarian purposes, frequently break off inside the hole. Heretofore it has been difficult, if not impossible, to remove the broken bolts, thus necessitating the drilling of a new hole and the insertion of a new rock bolt with consequential delay and expense. The invention disclosed is a tool for removing such broken rock bolts which comprises a length of pipe having an internal diameter slightly larger than the diameter of a rock bolt shaft. A hollow cylindrical insert of hard material extends from the mouth of the pipe at least part way along the length of the pipe and has an internal diameter such that it may be force-fitted over a rock bolt shaft, as by hammering the end of the pipe. Also, at least one inwardly directed tooth of hard material is provided back from the mouth and extending slightly into the interior of the cylindrical insert, which tooth digs into the rock bolt shaft to assist the tool in unscrewing the broken rock bolt shaft, e.g. by means of a handle passed through diametrically opposed holes in the pipe adjacent to its other end.
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