The pipe thread standard is derived from the British Wyeth thread and is the basic size for measuring the pipe thread size. Usually in a 1/16 taper relationship, the radial diameter tolerance of the Wyeth thread is converted to the axial tolerance of the inch seal pipe thread.
55 degree pipe thread: It is mainly used for pipe connection, so that the internal and external threads are tightly matched, and there are two kinds of straight pipe and tapered pipe. Common pipe threads mainly include the following: NPT, PT, G, etc.
Pipe threads are divided into the following three categories:
1. Inch pipe thread (55°)
Including: general sealed pipe thread (R), unsealed pipe thread (G), old British pipe thread (PT, PF)
2. American pipe thread (60°)
Includes: General Sealed Pipe Thread (NPT, NPSC), Dry Sealed Pipe Thread (NPTF, NPSF, NPSI, PTF-SAE SHORT), Unsealed Pipe Thread (NPSM, NPSL, NPTR, NPSH, NH, NHR)
3. Metric pipe thread (60°)
Includes: general sealed metric pipe thread (MC, MP), unsealed metric pipe thread (M).
Refer to the Handbook of Metric, American and Inch Thread Standards (Third Edition)
China's old mechanical drawing standard: 55° sealing conical pipe thread code is ZG, 60° general sealing conical pipe thread code is Z,
China's new mechanical drawing standard: 55° sealed conical pipe thread changed to column internal thread/cone external thread (RP/R1), taper internal thread/cone external thread (RC/R2); 60° general sealed conical pipe thread code For NPT (refer to American standards). For details, please refer to GB/T 7306-2000.
The new and old 55° unsealed cylindrical pipe thread code is G.