| 摘要 |
A bit assembly for drilling a hole into soil or rock comprised of an inner bit (2) rotated by a drilling aggregate, and of a ring bit (1) which can be locked in and detached from the inner bit, whereby the locking between the bits can be opened and the inner bit pulled out from the hole while the ring bit remains in the hole and where there is between the bits a face (e, e') transmitting axial force in the drilling direction from the inner bit to the ring bit. The system, for instance hollow (11) or corresponding elevation (5), has a slanting counter-surface (10) in order to eliminate backlash in drilling situations and to produce uninterrupted tightening for the axial-force-transmitting faces of said bits, and that the counter-faces of said elements, either of the hollow or the elevation, prevent partly or completely ring bit and/or protection tube (12) from moving farther than the inner bit.
|
