Having checked my tables I'm having some trouble identifying a thread. It's on a connecting pipe inside an airline regulator in the UK. It's a male thread on a plastic pipe that screws into the metal regulator body. Tpi is 18. OD is 0.835 inches. Fo you agree this this is 1/2 NPT? - it doesn't look tapered but it's only a short 1/2 fitting so hard to be sure. TIA!