Mac, I do similar all the time. Sometimes I don't look before I leap. Sometimes I misspeak. So I may or may not have a suggestion. My training, which I sometimes forget, is to thoroughly understand the problem. In doing this, a person sounds dumb sometimes. These questions are for anyone to answer.
1. In that picture, that thing with a dial is the gauge, what is that other thing with female threads. Is that the piece you are trying to mate to the gauge?
2. I would expect an old gauge to have pipe threads.
3. Does anyone know the exact size and type of the male threads on the gauge and the exact size and type of threads on the mating female part? It seems unverified. So can't continue until those are known and stated for sure.
4. What is that thing sitting on the glass?
5. Why is the desired gauge, a compression gauge instead of a pressure gauge?
6. You say you picked up a gauge, then say "dump valve" in the same sentence. Which part in the picture is a dump valve?
