Difference between NPT and BSP

[snyper]

This is an original thread from the yellow forum that I am qouting:


Most of the BSP threads used in airgun stuff are the straight thread BSPP so there wont be any taper to the thread vs the NPT which has a taper to it. Other than that it is pretty hard to tell because the threads per inch is pretty similar between the two of them. If you have some calipers and measure the thread towards the end and also up by the top of the fitting you should be able to tell from the measurement if it is tapered or not.

Here are some quick differences between some BSP and NPT threads

1/8 BSPP is 28 threads per inch and has a major diameter of .383
1/4 BSPP is 19 threads per inch and has a major diameter of .518

1/8 NPT is 27 threads per inch and has a major diameter of .405
1/4" NPT is 18 threads per inch and has a major diameter of .540

Again BSP has a 55° thread angle and NPT is 60°

As you can see as far as the TPI and Diameter it is pretty hard to tell the difference without seeing the taper of the NPT thread.


Here's the original LINK:

[alexbarb]

Nominal Pipe Size is loosely related to the inside diameter of Schedule 40 pipe. Because of the pipe wall thickness, the actual diameter of the threads is larger than the NPS, considerably so for small NPS. Other schedules of pipe have different wall thickness but the outer diameter and thread profile remain the same, so the inside diameter of the pipe is therefore different from the nominal diameter..
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Have a look at: sliding lock | npt threads .