Is the NPT used in United States Pressure Gauges parallel or tapered?
The following is the unattached photo.
When I attached the adaptor which is NPT to BSP converter. It is not all the way when tightened, not even half. Is the Pressure gauge thread tapered and the adaptor parallel? Or vice versa? how do I tell?
Best Answer
It's pipe thread - i.e. tapered, NPTM, unless you have an oddball gauge. Size depends on the gauge.
How do you tell? Measure it.
No idea what you have for an adaptor internal thread.
How have you "tightened" it - Hand tight? Using wrenches? Clearly not using pipe dope or teflon tape, one or the other of which is required to actually get a seal.
If you refer to the Wikipedia page linked, you'll note that 1/8 and 1/4 (likely typical sizes) have about 3 turns difference between "hand tight" and "effective thread length."