UNC: Unified Coarse Thread 5/16: Nominal size of the thread, in inches 18: Pitch of 1/18, meaning 18 threads per inch 3A: Tolerance grade, level 3, external thread (B is for internal thread) R.H: Right-hand
What Are the Differences Between Metric Threads and Imperial Threads?
Metric threads are represented by pitch, while American and British threads are represented by the number of threads per inch, which is their biggest difference. Metric threads have a 60-degree equilateral profile, while imperial threads have an isosceles 55-degree profile, and American threads have a 60-degree profile. Metric threads use metric units, while American and British threads use imperial units. Pipe threads are mainly used for connecting pipes, with tight fits between internal and external threads, available in straight and tapered types. The nominal diameter refers to the diameter of the connected pipe, and obviously, the major diameter of the thread is larger than the nominal diameter. 1/4, 1/2, 1/8 are the nominal diameters of imperial threads, measured in inches. The best method is to measure the distance between two thread peaks. If it is an integer or a decimal that can be divided by 5, then it is a metric thread, e.g., 1MM, 1.5MM, 1.75MM, 2MM, 2.5MM, 3MM, 3.5MM, 4MM.
Issues with Tapered Imperial Threads
1. BSP is the British Standard Pipe thread. However, there are distinctions such as BSP.Tr., BSP.PI., and BSP.F. BSP.Tr. is a tapered pipe thread used for sealing joints. BSP.PI. is a parallel pipe thread used for sealing joints, having only internal threads that fit with the external threads of BSP.Tr. BSP.F. is a parallel pipe thread used for general connections. Just knowing BSP is not enough; it’s best to confirm in detail. Otherwise, if there’s an oil or gas leak, it could lead to major issues. 2. The G thread and the BSPP thread are both codes for British cylindrical pipe threads with a thread angle of 55 degrees. 3. How many types of imperial threads are there? What are the characteristics and representations of BSP threads? There are two types, BSPP (pipe thread) and BSPT (55-degree tapered pipe thread, which is not compatible with the American 60-degree tapered pipe thread NPT). 4. Comparing G threads and Rp threads, what similarities and differences exist? Are there distinctions in their applications? Can they be used interchangeably? G threads and Rp threads are both 55° cylindrical pipe threads. The different codes arise from different countries (organizations). G is the code for China, France, the former Soviet Union, and Japan; PF is the code for Japan; BSP, BSPP are the codes for the UK; R, K are the codes for Germany (R is for internal threads, K is for external threads); TPYБ is the code for the former Soviet Union; Rp is the ISO code. 5. What is the difference between 1/8 and NPT 1/8 threads? They should now be national standards, but in the old NPT standard, it was called Z, which is a 60-degree thread sealing tapered pipe thread, national standard number GB/T12716-2002M, while G is a 55-degree non-thread sealing cylindrical pipe thread, national standard number GB/T3707-2001. 6. Is the English code for the British standard pipe thread BSP? Does it have a taper? The code should be G, cylindrical pipe thread, with no taper. 7. What are the differences between Rp threads and G threads? Can they be used interchangeably? Additionally, what is the difference between Rp and Rb, and can they be used interchangeably?
Pipe Threads are non-thread sealing internal and external pipe threads, characterized by the code G. G1/2 indicates cylindrical internal pipe threads; G1/2A indicates cylindrical external pipe threads. Used for threaded sealing pipe threads, Rp indicates cylindrical internal pipe threads; Rc indicates tapered internal pipe threads; R indicates tapered external pipe threads. Example of thread codes: G1/2-LH indicates non-thread sealing left-hand internal threads, with a size code of 1/2 inch. RP and RB cannot be used interchangeably because one is 55-degree thread and the other is 60-degree thread.
Are “Imperial Threads” and “Pipe Threads” the Same Thing?
ZG is the first letter of the Chinese pinyin for tapered pipe. It means tapered pipe thread. 3/4 refers to three-quarters of an inch, indicating the internal diameter of the pipe is 3/4 inch. Technically, its internal diameter is 19.05 mm, but this is an old standard that is no longer used. The current national standard states that ZG3/4″ thread internal diameter is 20 mm. Its representation should be: ZG3/4″. Where (″) is the symbol for inches. One inch equals 25.4 mm. One inch equals 8 parts. The origin of 3/4 is 6/8=3/4, commonly known as 6 parts.
Similarly, the internal diameter of ZG1/2″ thread is approximately 15 mm, commonly known as 4 parts. The internal diameter of ZG1″ thread is approximately 25 mm, commonly known as 1 inch. The internal diameter of ZG11/2″ thread is approximately 32 mm, commonly known as 1.5 inches. Tapered pipe threads are only used for hydraulic system connections; while pipe thread G3/4″ is only used for water pipe connections. Tapered pipe threads and pipe threads are very similar, differing only in the taper. All pipe threads are imperial!!!!!!!!!!
Source: Metal Processing
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