| 摘要 |
A drilling apparatus, especially apparatus redrilling an existing hole, in the drilling head of which there is, as the first advancing part, a cylindrical unit (4) with a diameter substantially smaller than that of the hole or the tunnel which is to be redrilled, and dimensioned to fit inside the original hole or pipeline (3) and by means of which unit steering forces from the walls of the original hole (3) steer the whole drilling apparatus.
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