crazyal
Super Member
Thanks for your advice!
I took out the safety relief valve and found it is specified in Metric and is stamped in tiny letters, BSP, British Standard Pipe. That thread is also used in Japanese cars and tractors and apparently by the Chinese when they clone stuff.
BSP 1/4" is almost compatible with 1/4" NPT, the American standard. I think the thread pitch is one more thread per inch. I found with oil pressure test gauges some NPT threads will screw into BSP and seal, at least for testing oil pressure, while another NPT fitting will be slightly too fat to catch the first thread.
So since the pressure relief valve is BSP I gambled that the whole assembly is that thread as well. I ordered this replacement pressure switch via Ebay. At only $12.50 its not much of a gamble.
1/4" BSP 4 Port Single Phase Air Compressor Pressure Switch + Safety Valve Gauge | eBay
And as you suggested, I may still need a handful of adapters before I am back to running a reliable pressure switch.
I remember hearing about (I think) a B29 bomber that landed in Russia. The Russians were so afraid of their leaders and didn't want to get something wrong so when they reverse engineered it to copy it they even copied the Boeing logo on the yoke (translated into Russian) because they didn't know any better. Sounds like the Chinese copied the Russians methods for reverse engineering.