Drill string with threaded coupling, has external and internal threading with sawtooth geometry

摘要

The external and internal threading (3, 8) is formed by multiple threads (15) with a slight conical form that generate a sawtooth geometry and have a high incline. The drill string (1) is used to bore holes in unstable formations, especially in layers carrying a lot of water, and is especially suitable for overlapping drilling. A journal (2) at one end of the drill string is provided with external threading (3) between an outer shoulder (4) and a journal end surface (5). A bushing (7) at the opposite end of the drill string is provided with internal threading (8) between an inner shoulder (10) and a bushing end surface (9). The external and internal threading have a conical shape and include thread-free guide sections (6, 11).