| 摘要 |
<p>PCT No. PCT/SE82/00021 Sec. 371 Date Sep. 17, 1982 Sec. 102(e) Date Sep. 17, 1982 PCT Filed Jan. 26, 1982 PCT Pub. No. WO82/02735 PCT Pub. Date Aug. 19, 1982.A drilling assembly for use in percussion drilling comprising a drill bit and a drill rod having cooperating conical surfaces, one of said surfaces being provided with a helically extending thread. For purposes of ensuring a reliable connection the thread meets certain geometrical demands and is designed as a left hand thread. Further, the conical surface being provided with the thread is harder than the other conical surface.</p> |
