1/2in NPS valve required for 72
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half inch
2airishuman
Contributor
I wonder whether some of the threads in this old thread are actually M18.
I just picked up a Norris 2250 72 with an original hydro of 1975. What valve is this going to have? I took it in for visual and hydro yesterday and need to put a DIN valve in it. The guy that I got the tank from gave me a DIN valve to replace the old yoke valve. Any idea where I can find definitive information on this tank?
As far as I know, there were only 3 neck threads used on the old 72s... 1/2 NPT (taper thread, easily recognized by the exposed threads when installed), 1/2 NPS (uncommon; Sportsways, Healthways, and White Stag.... And only for a short time period. Recognizable by an unusually narrow neck.), and 3/4-14 (modern standard). With a 1975 born on date, I'd bet you a dollar it's 3/4-14. Incidentally, those designations are based on pipe inside diameters, so a 3/4-14 valve actually measures a little over 1 inch at the threads.
Respectfully
James
2airishuman
Contributor
I have never seen a 1/2 NPSM thread on a cylinder and am skeptical that this thread form was actually used. M18x1.5 threads were used on some earlier (1960s) scuba cylinders including some I have had in my possession; I confirmed the thread size by using an M18x1.5 tap as a thread gauge.
M18 threads are also used on SCBA cylinders. They are slightly smaller than 7/8" UNF.
M18 threads are also used on SCBA cylinders. They are slightly smaller than 7/8" UNF.
Below are pages from the 1961, 1962 and 1963 Sportways catalogs. They all refer to 1/2" Standard Pipe Thread and 3/4" straight thread.
In 1961 it is fairly safe to assume that we did not use any metric threads in the US.
An interesting thing that is not normally known is that even the DIN connection that has been very popular in Europe (and recently made it to the US) also predates the use of metric threads. The DIN fitting uses Imperial threads. When I started using the DIN fitting in the 70's it was not even called DIN at the time.
In 1961 it is fairly safe to assume that we did not use any metric threads in the US.
An interesting thing that is not normally known is that even the DIN connection that has been very popular in Europe (and recently made it to the US) also predates the use of metric threads. The DIN fitting uses Imperial threads. When I started using the DIN fitting in the 70's it was not even called DIN at the time.
Thank you! The valve on it was a yoke valve that looked pretty standard and there were no exposed threads. The DIN valve I took to the shop for them to replace was a straight valve that measured just over an inch wide at the threads. It had an O-ring at the top of the threads. It sounds like it should work just fine. Thanks!
ScubaBunga
Contributor
I ended up with ordering some 115 size that are working great.
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