| 摘要 |
A V-shaped frame (102) is attached to a pipe (100) to be drilled. The frame may be used with larger pipes by attaching a removable extension plates (120) to the arms (104) (106) of the V-shaped frame, thereby increasing the size of the recess between the arms (104, 106). The apparatus may be fixed to the pipe (100) by a chain (110) which connects to the platform (102) and extends around the pipe (100), or by attaching clips to the frame and attaching the clips to the surface of the pipe by screws etc. To attach the apparatus to a pipe having a corrugated outer surface, clamp members (340) extend into the grooves (308'') of the corrugations to grip the groove walls (316).
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