| 摘要 |
Boring apparatus for forming a generally horizontal underground passage in soil for a utility conduit or the like that includes a tool head with a base portion and a nose portion mounted on the base portion. The nose portion is rotatable relative to the base portion between a first position in which nose portion surfaces are symmetrical with respect to the tool axis so that the tool will move along a straight path and a second position in which nose portion surfaces are in asymmetrical position with respect to the tool axis so that said tool will move along a curved path. By application of torque to the base portion, the base portion is shifted relative to the nose portion to shift the tool head from between an asymmetrical configuration and a symmetrical configuration.
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