Well that's an odd thread!

[Bki26]

Took one of the 136 bar tank valves off to figure out the threads, the outlet thread took a while as all dimensions matched up to 5/8-14 bsp AND 7/8-14 unf but I'm going with bsp being British made equipment (probably anyway)

The taper is a whole different nightmare as 14tpi is only part I can work out and it's roughly dropping from 0.78" to 0.63" over 0.9"

 

[Agroshield]

1/2" NPT is a possibility.

However, high pressure gas stuff has its own standards. What is the tank for? Scuba diving? Knowing the application will narrow down the possiblities.

See:

https://www.gewindebohrer.de/en/service/technische-daten/thread-type-w-cylindrical (note the popularity of 14 tpi in the list).

 

[8ob]

Took one of the 136 bar tank valves off to figure out the threads, the outlet thread took a while as all dimensions matched up to 5/8-14 bsp AND 7/8-14 unf but I'm going with bsp being British made equipment (probably anyway)

The taper is a whole different nightmare as 14tpi is only part I can work out and it's roughly dropping from 0.78" to 0.63" over 0.9"

If its a repurpose job just chase/tap out the internal thread on the bottle with a bspt tap.

Bob

 

[Bki26]

1/2" NPT is a possibility.

However, high pressure gas stuff has its own standards. What is the tank for? Scuba diving? Knowing the application will narrow down the possiblities.

See:

https://www.gewindebohrer.de/en/service/technische-daten/thread-type-w-cylindrical (note the popularity of 14 tpi in the list).

Its a 136 bar breathing air cylinder used for scba (not scuba)

If its a repurpose job just chase/tap out the internal thread on the bottle with a bspt tap.

Bob

The bottle thread is also tapered which is what got me confused and intrigued as to what this could be and easier job to just use as is with the 5/8bsp since it's one of the 20+ tanks I recently acquired cheaply and have had many sell already lol.

 

[Bki26]

Marked on the side of the valve I've just noticed is "SG&Co ltd which is Siebe Gorman the British company

 

[Agroshield]

This is what you want:

https://www.scribd.com/document/681902440/BS-341-Gas-cylinders-Cylinder-valves-Part-1

See Section 5 and figure 3.

Note that the threads are parallel to the taper rather than parallel to the thread axis for this type of thread.

Edit: if you did not already know, type 'scribd downloader' into google and follow your nose.

Edit2: the obvious place to look also comes up trumps:

Scuba cylinder valve - Wikipedia

en.wikipedia.org

 

[Bki26]

This is what you want:

https://www.scribd.com/document/681902440/BS-341-Gas-cylinders-Cylinder-valves-Part-1

See Section 5 and figure 3.

Note that the threads are parallel to the taper rather than parallel to the thread axis for this type of thread.

Edit: if you did not already know, type 'scribd downloader' into google and follow your nose.

Edit2: the obvious place to look also comes up trumps:

Scuba cylinder valve - Wikipedia

en.wikipedia.org

You beauty, mystery solved then I'd say!