I've got this piece in front of me that is off a locomotives whistle which has threads I'm not familiar with. These are tapered threads, but these aren't any designation which I can find. I've been told perhaps "Bridge Taper Threads" or "Steam Boiler Threads". Only thing I know for certain is this is for Locomotives which have steam boilers. This isn't NPT or BSPT nor is it NPTF. The outside of the largest diameter part of the thread is measuring pretty much exactly 2.500". I'm being told that there are 12 threads per inch, though I can't really verify that as there isn't really a full inch of threads going on here.
ST9 Windows 7 Professional Nvidia K2200 & Intel Xeon "You're doing it wrong"