Measure valve thread, please ?

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Hello.
Anyone with a valve removed from the tank at the moment; can you please measure the thread in your valve, not what the documents/specs may show on a web site link ? (a parallel one, not tapered)
Is it 0.700" or 0.740" or other ?

Measure.png
 
There are at least 4 straight threads that I am aware of that were used in scuba tanks, 1/2 NPT, 3/4NPT, 3/4 BSPP and M25. All are different and the last 3 are pretty close to each other so you need to be very careful when trying to figure out which you have.
 
In addition to Herman's comment (He's usually right from what I've seen here on SB. He knows his stuff.) there is also the slightly less common 7/8 straight thread that is on some of the 3500 psi tanks. Ironically it's actually smaller than the 3/4 NPT thread... go figure. It's 0.875-14 UNF which seems larger than what you're measuring... you sure it's not a tapered thread?
 
Thanks, fellows. Is not tapered. To add confusion, Wikipedia mentions a thread 3/4" x 16 UNF, which I have to suspect the 3/4" is not from measuring the thread, but one of those plumbing 'nominal' names.
What cylinders use the 3/4" x 16 UNF ? Do you know ?

Is there a valve for such 3/4"x16UNF ?
Seems there is nothing NPT
Diving cylinder Wiki.png
 
Thank you, runsongas. Interesting a medical oxygen cylinder being listed in Wikipedia under diving cylinders.
 
Thank you, runsongas. Interesting a medical oxygen cylinder being listed in Wikipedia under diving cylinders.

Some people don't know what they have, and guess. Buy a foreclosed storage area, or clear out a relatives house. I've got some good deals because s seller, from his POV, is just getting rid of crap.


Bob
 
3/4-16 UNF would be .750 since the UNF indicates its a screw thread dimension rather than a pipe thread.
I forgot about the 7/8. You have to be careful with valves since some will "almost work". If I remember correctly, the M25 will loosely thread into a 3/4 NPS but will come out under pressure. The 3/4 BPS will thread into a 3/4 NPS a few turns but stop......took me days to figure this one out. The size looks the same but the 55 deg threads jam after a few turns, you have to look hard to see the difference in 55 and 60 degree thread.
 
Herman is correct 3/4-16 UNF is a bolt thread just as 3/8-28-4 UNF used on PL hose connections is the same as what is commonly referred to as a fine thread as opposed to course thread. A 3/8-16 UNC is coarse thread.

UNC and UNF - Unified Inch Screw Threads
 
https://www.shearwater.com/products/teric/

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