Premium connection includes thread, sealing surface and shoulder. The processing technology is complex. For example, when the coupling is processed, the distance between the thread and the sealing surface is relatively close, and a special undercut is generally designed at the end of the thread. The raw material requirements of premium connection are API based, but higher. Because of the unique shoulder structure of premium connection, it requires a large thickness of raw materials, which leads to a large amount of boring and cutting during the processing of coupling, a large cutting resistance, and serious processing hardening, which directly affects the roundness of the finished coupling.
The cutting tool and measuring tool of premium connection are different from the common API thread, because there are sealing surface and shoulder part, the increase of coupling length will increase the machining distance, and the corresponding length of cutter bar will also increase correspondingly, which is easy to cause problems such as twining lines, poor surface finish and machining accuracy, and it is difficult to use the thread comb with larger cutting force to process coupling.