| 摘要 |
<p>In the present invention, in a drill rod for a boring machine, a rod outside diameter is large so as to be approximately equal to a bore diameter, external threads are provided at one end and internal threads are provided at the other end, and at least one small-diameter portion is formed near an internally threaded portion. This step tube rod can reduce a bore bend. <??>Also, for the boring machine using this step tube rod, the drill rod can be positioned easily, so that the connection and recovery work can be performed efficiently and safely. <IMAGE></p> |
