| 摘要 |
Abstract A drill bit for a drill assembly including a friction bolt defining a longitudinal axial passage, the drill bit comprising a first bit body at its leading end said first bit body including a first cutting part and being adapted to releasibly engage with a second bit body; wherein the drill bit is adapted to pass through the longitudinal axial passage in the friction bolt. nL ) C(N (O cL (No (No (NL I(N (ND |
