THREAD COUPLING FOR DRILL STRING ELEMENTS FOR PERCUSSIVE DRILLING

摘要

Thread coupling for percussive drilling. The thread coupling comprises a first drill string element (2) with an internal thread (3) and a second drill string element (6) with a spigot (7) which is privided with an external thread (8) for cooperation with the internal thread (3). A contact surface (10) on the second drill string element (6) is lined with a wear resistant additional material which covers 50-100%, preferably 50-90%, of the contact surface. The wear resistant material is preferably a stellite which has been applied by means of plasma welding or which is a ring which has been soldered to the contact surface.