Thread structure for percussion rock drilling

摘要

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