Another antique plumbing question(fine thread brass)

Vitaliy2

Good afternoon everyone!
I'm a caretaker of a 19th century victorian mansion in New England. There's quite a bit of threaded brass pipe still in service(essentially all hot water lines and some cold water as well).

Recently, I needed to replace a failed CI drain line to a utility sink in the basement laundry room. After repairing the floor slab, the sink now sits about an inch higher than before(the floor is concrete, with a layer of asphalt on top and the sink legs were embedded in that asphalt)

Long story short, I need to shorten two brass nipples that lead to the unions that connect to the sink(of course I can just redo all of it in copper, but as an engineer, its more important for me to preserve mechanicals than even interior finishes in this house)


However, I quickly realized that both the nipples and the fittings(valves and unions) are not NPT. Here it is compared to the regular NPT brass nipple:

After some research, I found a mention of 'fine thread brass'(https://www.plbg.com/forum/read.php?1,456635) that was common here in Boston area. That does seem to fit the bill.

Does anyone have any experience with it? Is it possible to get dies for this type of thread? Or maybe there's an official name for it, so I can determine what the pitch and so on is and then maybe cut it on a CNC lathe or something.

Thank you very much!

mattmia2

I'd just shorten the copper be low it, looks like you have plenty of room for that.

You could always cut the threads on a lathe.

neilc

I get the "love of the old building" thing,
but, aren't you feeding a new stainless basin, with no historical value?

mattmia2

Unless they want to replace all of it, they will need to transition to it eventually. I suppose you could thread one end of an old piece npt then use modern fittings from there. heat it with a torch to anneal it first.

Might want to look in to why on this old house in like 1982 they said you were really lucky that fine thread brass didn't crack.

Vitaliy2

I believe the stainless steel sink is fairly old too. This house was a doctors residence for much of the 20th century and the carriage house was the clinic. The room in the picture was the main laundry for the whole operation. They pretty much stopped by 1960s so the sink must be from that time

Vitaliy2

The brass is in a decent shape. Didnt have much issue disassembling everything

Jamie Hall

I've seen that fine thread before... in fact, I have some. But I was fortunate in not having to try to fit it to a modern fitting. I've looked all over, and I'm sorry but I can't find the exact spec. on it. If you can determine the thread profile -- it may be a V rather than the modern NPT rounded profile -- a clever chap with a machinist's lathe could duplicate it. If you have a really first class railroad model hobby shop around, you could ask if they know of someone with a Unimat...

Pumpguy

As @Jamie suggested, anyone with a screw cutting metal lathe would be able to cut those threads for you.

Aside from professional machine shops, you might check into the home shop machinist and model engineering fraternities. There are several forums found online.

If you still need help, contact me via PM or phone at number below. I should be able to do it for you.

mattmia2

You could also figure out what copper tube or fitting size will slip over the outside of the brass and sweat it to the copper then adapt from there.

ChrisJ

If it was mine I'd either be modifying the sink, or those copper lines.
I'd probably already have two couplers on the copper lines, to be honest.............

I really do not think you want to go the machine shop route.

JUGHNE

IIWM, I would cut about an inch (as needed) out of the copper tubes that comes out of the top of the sink, solder in a coupling for each and there you are.

IMO, you are over thinking this.

The copper and sink are not original to the house anyway.
The sink is old, probably from the 60's as you guess.

Vitaliy2

Thanks for great thoughts and ideas everyone! Yeah, cutting and resoldering copper was my original plan, and I will probably end up doing that. But fine thread brass got me excited since I haven’t dealt with that before and thats exactly the kind of craziness I like to do(along with pouring cast iron lead joints just for fun)

Its unfortunate that theres so little info about it. I also wonder if some antique threaders/chasers I see at flea markets and such are for this type of thread.

neilc

Vitaliy2 said:

along with pouring cast iron lead joints just for fun

ah, pouring and huffing lead are ya?
starts to explain your fine tread brass desires,
#smirking

Duckbutter

I just happened on this thread for the fact that I'm a licensed plumber in Ma and happen to be working a job with fine threaded brass piping.

Fine threaded brass isn't just a Massachusetts anomaly, but more a small regional one, specific to North-west Boston, in the Lexington, Arlington, Cambridge MA area, though I could stand corrected there.

We use what are called "Reamed" adapters, the threads are "probably" 12 tpi, maybe 10, and to answer the original question, you'd have to get custom made dies or have the nipples made with a lathe, these are not NPT standard.

PC7060

mattmia2 said:

You could also figure out what copper tube or fitting size will slip over the outside of the brass and sweat it to the copper then adapt from there.

What Matt said. I had to get creative when repair a 1920s vintage tub spout with a fine pitch. I used a 1/2” brass pipe as an inner sleeve soldered to the original brass. I breathe a sigh of relief when that job was over.

mattmia2

Seems like you could use tubing to slip over an existing nipple and solder to it and adapt to copper from the tubing.

which it looks like i suggested 2 years ago.