| 摘要 |
A collapsible cutter bit or rock head for use with an underground auger boring machine has an expanded position for cutting rock in front of an underground pipe and a collapsed position for withdrawing the rock head through the underground pipe. The auger boring machine is configured to bore a passage through a body of soil and rock and simultaneously lay the underground pipe in the passage. Forward rotation of the cutter bit causes expansion while collapse of the cutter bit may be driven by reverse rotation of the cutter bit or another mechanism.
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