Hello here’s some info I’m copying from google but I work at a ace hardware and run into this issue a few times.
I found this to explain things more proper but conveying the same info I know.
“BSPT equivalent is NPT and BSPP’s equivalent is NPS. Never swap threads if it is a high pressure application. NPT/NPS and BSP threads are not compatible due to the differences in their thread forms, and not just the fact that most sizes have a different pitch.”
BSPT (British Standard Pipe Thread) is similar to NPT except for one important difference. The angle across the flanks of threads (if you sliced the fitting in half long-ways and measured the angle from root to crest to root) is 55 degrees instead of 60 degrees as it is for NPT.
Added: ALL OF THESE OPTIONS VOIDS WARRANTY AND BECOMES PERMANENT!
Your best options here are-
If both items are metallic you can always “heat weld” them together but this you can not use thread tape as it would melt /exhaust fumes. But you heat both metal objects to nearly red. Of course using tools / leather / furnace gloves begin to attach both piece and twist, when it reaches the point it can’t easily tighten and you force tighten it, it begins to “weld” the pieces together.
If it is plastic to metal OR plastic to plastic -
Add thread tape and force tighten pass the “hard to tighten stage” using a table vice or something similar and just crank on it safely and allow the materials to cross thread and pray the 100psi doesn’t blow it.
Or similar heat weld as mentioned above… it’s harder on plastic to plastic but you heat up (don’t use direct flame as this would melt the plastic near instant) the male end and tighten as necessary (sometimes you can get the plastic hot add some thread tape that sorta melts instead in, then tighten female on.
Metal to plastic, heat um the male end and attach female and thisbbasically melts the plastic to form a seal.