Tubing thread is a kind of connection thread with close connection and good tightness. Its advantages are easy assembly, high connection strength, interference combination, no special filler, proper deformation of thread or sealing grease can ensure good sealing performance, and can be duplicated quickly. If there is enough clearance, it can be used. Axial displacement compensates pitch, taper, pitch and tooth angle errors, so this thread is widely used in oil industry and drilling equipment manufacturing industry.
The main factors affecting the sealing performance of tubing threads are as follows:
1. Tooth profile error of tubing threads;
2. Taper error of tubing thread;
3. Pitch error of tubing thread;
According to the factors affecting the sealing performance of tubing threads, we focus on improving the pitch accuracy of tubing threads, and rationally configure the parameters of the top and bottom flattening height of the internal and external comb knives as breakthrough points, the re-grinding, installation of tubing threaded comb knives, the processing of vertebral bodies, the fine turning of tubing threads, and the quality inspection of tubing threads. A series of control measures have been taken in the aspects of measurement, pressure test specification and process specification perfection. Under the condition of common mould lathe and simple NC lathe without any API single measuring instrument, tubing threads meeting the requirements of API standard have been processed.