Originally Posted by Limecc
I agree with you SP but otherwise you posted misinformation.
American National Pipe Thread (NPT)
British Standard Pipe Thread (BSP or BSPT)
1. Either (male) thread can be tapered. This is the norm for pipes.
2. NPT has a 60deg thread angle, BSP 55deg. Sounds a small difference but is in fact a big deal if you wanted mismatched fittings to hold pressure. (taper takes care of any OD diff)
3. The threads per inch (TPI) is not always the same
Yes, and that's why I run a tap down them.
Like BSP and UNC same pitch and dia different thread form.
Changing the thread form doesn't alter the strength, in fact I did it on an airline about a month ago to set up my compressor to pump up my RIB.
The gauge I ordered had what my fittings supplier called "Chinese Metric" and nothing seemed to fit. Yep a Tap and Die set fixed it.
Incidentally I do try to obtain the correct fittings if possible.
That's the only time I wished I wasn't retired, because I was a machinist and could machine up any fitting I wanted.