Thread: 1/2" UNF oil pressure sendor unit?

It's actually a taper pipe thread, 1/4" NPT. I used to fit Ford Falcon pressure switches back in the day when they turned up regularly. 1/2" UNF resembles the thread quite closely but of course isn't tapered, wheel nuts in that size make excellent drain bosses for fuel tanks as the 1/4 NPT tap would start in the existing thread.

Originally Posted by bee utey

It's actually a taper pipe thread, 1/4" NPT. I used to fit Ford Falcon pressure switches back in the day when they turned up regularly. 1/2" UNF resembles the thread quite closely but of course isn't tapered, wheel nuts in that size make excellent drain bosses for fuel tanks as the 1/4 NPT tap would start in the existing thread.

Thanks.
The thing is it is definately 20TPI, not 18TPI as 1/4" NPT is. I have a 1/4"NPT adaptor and it won't match up.

Maybe BSP which is 19TPI.

Just to clarify, I am trying to fit a new sensor where the LH sensor is in the attached photo. I am perplexed as to what this sensor is for as it looks like a oil pressure gauge sender unit but there is no gauge in the vehicle, and the wiring terminals look "factory". Disconnecting it makes no difference to lights operating on the dash, the oil pressure warning light being activated by the switch arrowed on the RH side.

Of course! Your front cover is Land Rover, nothing to do with a P76 engine. I just happen to have a LR oil pressure switch here I'm installing into a D2 tomorrow, and it fits perfectly into a 1/2" UNF wheel nut. I suggest you find a dead one of said switches, cut off the plastic end, drill it out to 11/32" and tap it to 1/8" NPT. Problem solvered.

Might just grab a 1/2" UNF bolt and drill the centre out in the lathe, then tap the inside at 1/8 NPT. If I use a short enough bolt I could even leave the head on it so I can use a spanner to tighten it.

The seal is a flat aluminium washer so make sure the thread goes all the way to the head. Thread seal doesn't work very well on parallel threads.

1/2" UNF is a common thread size for hydraulic fittings. It matches the -5 size fitting. A -5 ORB fitting would work. Land Rover uses the size very frequently on fuel fittings.