Joel wrote:NPT - national pipe thread is some crappy old imperial system
actual thread diameter isnt 1/8" i got no idea how NPT works
but its what most cars use
You got it Joel but it really isn't some old crappy imperial thread! It is still the current thread used on pipe fittings in this country as well as many overseas ones. It just depends on which country it originates from. NP = National Pipe thread which of course is the American Standard. Here in Australia, we normally use the British pipe threads which is BSP = British Standard Pipe. If you get pipe fittings from hardware stores here, in most cases they will be BSP whereas auto fittings can be the NP ones. The British system adds a "P" for the parallel thread. The Americans add an "S" for STRAIGHT thread. Both systems also have tapered threads as well as parallel ones eg. BSPT and NPT.
The oil pressure switch on our VW is M10 x 1 as are the brake lines from memory which is only a couple of thou difference in pitch to the 1/8" NPT. I'm sure there have been many NPT and even BSPT been screwed into the oil pressure switch position!!
The bloody Yanks couldn't agree with the Poms on the pitch and had most smaller ones 1 T.P.I different! The OD also varies a bit on most. As Joel mentioned, the size given is the NOMINAL BORE of the pipe.................... but you guys knew that stuff anyway.
A bit of info here for the workshop wall!
http://academic.evergreen.edu/projects/biophysics/technotes/fabric/pipe.htm
DH
