I have this compressor valve which dates from 2009. It got screwed on too hard and finally split. I'm looking to replace it either by another such valve or just an adapter to 1/4" NPT. I'm just unable to figure out the threading standard of the female side (non-NPT). I took some measurements and compared with a variety of standards. None of them comes close enough to be a match.
I've got the following measurements:
- Internal diameter seems to be about (or slightly more than) either 1/2" or 13 mm. Don't think it's tapered, but I might be wrong. Since it's split and I don't have the counterpart (helping my uncle find a replacement), it's a bit hard to tell.
- Using thread pitch gauges, the best matches I get are either 27 TPI or 1 mm.
It's not significantly closer to imperial or metric to help me guess which it might be.
It's like a hybrid of BSP 1/8" for the threading and BSP 1/4" for the diameter. That's the best I can tell, which isn't useful to find a replacement.
EDIT 2024-06-11: I might have found what that thread is. Can't fully confirm, but that looks a lot like BSB 1/2" (British Standard Brass). That's an interesting standard where the thread pitch stays constant regardless of the diameter of the pipe, reducing stress on the pipe wall to save brass on larger pipes.
My uncle went around the city to every hardware store and to the more industrial shops that might have such rarer parts for sale: shrugs all around or suggestions to use NPT.
I've communicated with King Canada, which is the maker of this compressor (model 8489). They've replied with a shrug. It would be the part #88 in the service manual.
A couple pics for a visual:
