| 摘要 |
A bit assembly of a device boring a tunnel or hole in the soil comprising a cylindric inner bit (11) that can be pulled out from the bit assembly and a ring bit (10) mounted substantially outside the said bit to drill the outer hole portion and through which bit assembly drill waste is transported backward by means of pressure medium, s.c. flushing medium. The flushing medium channels (19) are in spindle (29) to discharge from there to the front side of the bit assembly, substantially from the outer bit circle, for instance the space between ring bit (10) and inner bit (11), and that the flushing medium is conveyed from the front of bits (10, 11) backward through bit spindel (29).
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