| 摘要 |
This invention relates to a down-the-hole hammer drill, and has particular application (but need not be limited) to a reverse-circulation (RC) down-hole face sampling hammer drill. More particularly, a bit for the percussive down-the-hole hammer comprises an elongate shank, a head, at least one channel extending lengthwise along the shank toward the head, wherein the width of the or each channel is reduced at a position toward the head, so as to create a narrower channel portion extending from this position to the head, and a wider channel portion extending to this position, and define at this position a contact area in an end of the wider channel portion for contact between the bit and a portion of a driver for the bit. An associated percussive down-the-hole hammer comprising a splined drive sub, is also disclosed. |
