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Slightly obscure plumbing question here.
What are the threads typically used for the nuts on brass compression fittings?
Obviously the threads for joining bits of brassware together are BSP (taper or square). But the nuts on compression fittings do not normally (ever?) use those threads. They are quite similar, and annoyingly, not always consistent across fittings/manufacturers. Sometimes they do match up. I suspect there are a fairly small number of threads in use and it would help me if someone knew what those were.

I ask because I've got quite a lot of fittings that have been recovered or salvaged and they often lose their nuts in this process (trapped the wrong side of an olive on some other bit of pipe). At least in principle one could rejuvenate these things with the right nuts, which _ought_ to be quite cheap (but probably aren't in practice unless you buy 1000).

I've just measured a few threads and wandered around some thread charts online with limited success so I thought it worth asking in case someone has already been down this road and found out. The fact that threads _are_ sometimes the same across manufacturers makes me think there aren't actually that many options.

Anyone know?

Typical is BSPP but this can be a can of worms. Some use a finer thread which I think is British Standard Brass Thread, there are also metric ones - and some use NPT the us variation. It also seems to vary with size, 15mm pipe using 1/2" BSPP but larger sizes seem less consistant.

The nuts can be readily purchased, for example: https://www.bes.co.uk/catalogsearch/res ... sion%20nut

I too am a re-user of compression fittings -especially if awkward to solder / repair........
Olives are cheap (screrwfix) . If i cannot match nut threads im afraid it enters the scrap brass pile but not often.
Am i the only one who sorts copper scrap into clean / soldered/ painted ecr before the bi-anual trip to the scrap yard ?
george

ecogeorge wrote: ↑Thu Feb 10, 2022 6:56 am I too am a re-user of compression fittings -especially if awkward to solder / repair........
Olives are cheap (screrwfix) . If i cannot match nut threads im afraid it enters the scrap brass pile but not often.
Am i the only one who sorts copper scrap into clean / soldered/ painted ecr before the bi-anual trip to the scrap yard ?
george

I too like re-using fittings, and have bought a stock of replacement olives. (I have got some cast capillary-jointed fittings saved too, I think I have drawn on them occasionally. However, I learnt the hard way DON'T use capillary stop-valves: if you want to get them off in-situ you can't as water sits above one side and just boils...)
I don't go so far as to separate painted and unpainted copper! I do separate copper and brass, and was very pleased to be complemented for it by my friends at the scrapyard who gave me a better price for both! I always do it now, not that I actually generate much these days. I guess the next lot will be after moving my solar tubes and changing over to microbore pipes. (I did the original in 15-mm because I had most of the pipe and fittings needed in my bag of spares.)
A

ecogeorge wrote: ↑Thu Feb 10, 2022 6:56 am I too am a re-user of compression fittings -especially if awkward to solder / repair........
Olives are cheap (screrwfix) . If i cannot match nut threads im afraid it enters the scrap brass pile but not often.
Am i the only one who sorts copper scrap into clean / soldered/ painted ecr before the bi-anual trip to the scrap yard ?
george

I did the same George which proved worthwhile as there were varying prices for each with naturally clean copper being the highest priced.
When mixed together I believe the price generally offered is that of the lowest priced category. I suspect not all merchants necessarily follow this trend!