THREAD STRUCTURE FOR PERCUSSION ROCK DRILLING

摘要

A thread structure for interconnecting two elements (10) in a percussion drill string comprising an interior cylindrical thread (12) and an exterior cylindrical thread (13). The threads (12,13) have abutting flanks (19,20) which are straight along their abutting contact portions. The clearance (a) between the bottom portion (22) of the exterior thread (13) and the crest portion (24) of the interior thread (12) is large enough to ensure that contact does not arise at said clearance when the threads are worn. (Fig. 6)