Drill thread
The joint thread is used for connecting drill collars, drill pipe, drill stabilizers, and conversion top drilling items and drill string members. The current specification for production and inspection is API SPEC.The specification calls the drill joint thread "rotating shoulder joint", which is the mechanical organization of connecting drill string members in the oil drilling industry. This taper thread is characterized by axial displacement to compensate the diameter error of the connecting part, so it has high interchangeability, tight combination and easy assembly and disassembly. Its technical characteristics are British taper pipe thread, shoulder joint, triangle thread, which is widely used in pipe joint. The type of thread is as follows:
1) Digital thread (NC)
Digital thread is the API recommended preferred use of thread, all the standard selection of V-0.038R flat top round bottom triangle tooth type, the tooth type is characterized by a circular tooth base radius of 0.038"(0.965mm), taper 1:8, 1:6 and 1:4, applied to kelly pipe, drill pipe, drill collar, drill tool stabilizer and other drilling materials.
2) Regular thread (REG)
The thread of the joint of the drill is used to connect the internal thickened drill pipe, so the internal diameter of the joint of the drill pipe is smaller than the internal diameter of the thickened drill pipe, and the drill pipe is added.The inner diameter of the thick end is smaller than the inner diameter of the tube. API planned regular threads with the intention of using them for bit connection.
3) Internal flat thread (IF)
This type of drill pipe joint is threaded to the outer or inner thickened drill pipe, forming the inner diameter of the drill pipe joint, the inner diameter of the pipe body thickened and the pipe.A diameter of equal or approximate internal diameter. V-0.065 flat top flat flat triangle teeth are used for all standard threads. This type of teeth is Flat tooth base, top width 0.065 inches (1.65lmm). Divide by 5 Outside 1/2 if, interchangeability with NC thread. However, because the threaded tooth structure of this type is prone to stress concentration,API has replaced it with NC series.
4) Perforated thread (FH)
Although there are few standards for this type of thread, it was formerly widely used in faucets, kelly, drill pipe, drill collars, and drill bits. Now divide by 5 minus 1/2 FH and 6-5/8FH use V-0.050 tooth type, 1:6 taper of large standard thread, other are in the API eliminated thread list. The 4FH using V-0.065 thread is replaced by the digital NC40 thread as well as the internal flat thread.
