| 摘要 |
A platform for a drill is supported on four support members which are pivotable on the platform to alter the angle between opposite members. In one embodiment a stop limits the movement of the support members so that the maximum angle between them can be controlled to suit the diameter of a pipe on which the apparatus is mounted. In another embodiment, the support members are attached by connecting rods to a cross member which is raised and lowered on a threaded rod to pivot the members.
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