NPT Pipe Thread - The Size Difference Between UK And Us

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In order to know which thread is suitable for which pipe, it is important to know the pipe thread, which refers to the bore size of a specific pipe. It has to be very fine because the walls onto which they have been cut are very thin. The sizes in which they are denoted make many people think that they are very big, when they actually are almost microscopic. There is actually no relationship between the numerical diameter of the thread of a pipe and the size designation that has been given to it. If you are looking for the NPT pipe thread, it is very important to know that the NPT pipe thread in the United Kingdom and the United States is not the same.

The British sizes are most commonly used outside of the US and they come in two types. There is the BSPT and the BSPP. The BSPP refers to a NPT pipe thread that is parallel and are used in joints that are pressure tight and use sealing rings. The BSPT thread is more tapered and the threads are what achieve the pressure tight joint. It is quite common to see a prefix of either R for taper of G for parallel. This stems from German, where R stands for Rohr (pipe) and G stands for Gaz (gas). This is because the threads were originally designed to be used on gas pipes. When the term "NPT" is used, it often denotes the US measurement. The US also uses the NPSM thread. These are the two most common ones, but the US also uses GHT, NST and BSPT. Hence, it is very important that you know all the details about the threads that you are looking for, because it is all too easy to get the wrong one. Furthermore, it is also very much possible that the threads are marked as FPT (female threads) and MPT (male threads).

The reality is that a pipe size is not actually a physical dimension. Hence, a lot of highly specific measurements are needed to make sure that the right size NPT pipe thread is used. One of the tools that are used to check work pieces is the Go-No-Go gauge. Go and no go gages check whether the tolerance of a work piece is adequate. Go obviously means that all is in order and no go means it has failed the test. These tools are incredibly important in terms of quality assurance. Again, these gauges don't give an actual size, but rather a state, which is acceptable or unacceptable. These tools are most commonly found in the manufacturing industry because they are quite easy to use and hence invaluable in terms of working out thread dimensions.

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NPT Pipe Thread - The Size Difference Between UK And Us

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This article was published on 2012/03/28