Ok this is slightly off topic...but I know there is a wide variety of knowledgeable people on here.
A number of years ago I was given a collection of old Fire hydrant standpipe parts. I've finally got round to doing something with them (a short standard/reading lamp is the plan).
However I've discovered that not all the threaded parts fit together properly.
There is a blank cap which screws onto stand pipe perfectly, but the 2 instantaneous couplings only screw on about 1 1/2 turns before locking up. All the threads are clean and undamaged and none appear to be tapered. I assume the 2 couplings, originally came frome a different stand pipe, with slightly different threads.
Basically I'd like to fit all them all together, so that the couplings screw all way onto standpipe. I'm hoping that someone will be able to identify the threads on either standpipe or couplings, so I can then look out for a suitable tap or die as required.
7G whitworth thread gauge seems to match up reasonably well. I have tried internet search, but possibly due to the era these were made, there are a variety of threads shown, none which seem to match.
1. standpipe with one of the couplings screwed on as far as it will go..(1 1/2 turns)
2.Blank cap which is attached to stand pipe and fits perfectly.
3.coupling which I belive originally had a washer inside, so would have had to screw fully onto a standpipe to make a seal.
4. pitch of standpipe.