Specification for M25x2 neck thread

[Nick Ruberg]

Hi,
Does anyone have the exact specification for the neck thread of an M25x2 connection. In particular, the chamfer angle and depth as well as the tolerances.

I am making up a bench stand onto which I will screw in a pillar valve in order to make regulator servicing easier and more ergonomic.

Thanks,
Nick

 

[inka]

if it can be of any help .( pag 9/10 )

 

[inka]

later, i will measure in my tank, ( M25x200) diameter x depth where O ring sit

 

[BoltSnap]

I am making up a bench stand onto which I will screw in a pillar valve in order to make regulator servicing easier and more ergonomic.

When you have the chance, it will be nice to put up a diagram/picture of what you are making please.

 

[Nick Ruberg]

I have cylinders which I can measure but I wanted the manufacturing tolerances according to the ISO spec. I will gladly post a photo once finished.

What I am making is an item onto which a pillar valve will screw and it will have an incoming port (3/8 inch likely). This will be fed by a high pressure hose which will connect to the cylinder via a DIN fitting.

When servicing regulators I normally attach them to the cylinder to set the IP pressure and do checks but this isn’t ergononomic because the cylinder stands on the floor so you have to bend over. This item I am making will either screw onto the work bench or most likely have 2 flats which I can clamp on the bench vise and this will make it more pleasant to work. The unit can also be used to test pillar valves which have just been serviced without the need to charge a full cylinder to check them.

 

[BoltSnap]

I have cylinders which I can measure but I wanted the manufacturing tolerances according to the ISO spec. I will gladly post a photo once finished.

What I am making is an item onto which a pillar valve will screw and it will have an incoming port (3/8 inch likely). This will be fed by a high pressure hose which will connect to the cylinder via a DIN fitting.

When servicing regulators I normally attach them to the cylinder to set the IP pressure and do checks but this isn’t ergononomic because the cylinder stands on the floor so you have to bend over. This item I am making will either screw onto the work bench or most likely have 2 flats which I can clamp on the bench vise and this will make it more pleasant to work. The unit can also be used to test pillar valves which have just been serviced without the need to charge a full cylinder to check them.

Do you mean something like this?

H.P. Manager with Bench/Wall Stand

 

[Bob DBF]

I think more like this:
Scuba Valve Tester

The fitting that accepts the valve is bolted to the bench.


Bob

 

[Nick Ruberg]

Yes, very similar though I’m not going to provide for a pressure regulator. I have seen similar devices, but it will be a very quick and cheap thing to turn. Also, the vise design is so that when not in use, it isn’t taking up bench space. I just open the vise, coil the whip and put it in the drawer.

 

[TrimixToo]

Are you asking about the thread's class of fit? If it were me (it's not), I wouldn't worry too much about that; there are plenty of engaged threads. But I won't be using the result under HP, either, so pick your own level of worry (smile). I can't measure it conveniently, but my guess would be 6H. It's not a really loose fit and you can easily hand thread valves. I'd thread a scrap piece at 6H and see how it felt with an actual valve or two. (Valves and tanks are not incredibly consistent in feel during assembly, so my guess is that there's definitely some significant tolerance stacking going on industry-wide.)

[Edit] I belatedly realized that the neck thread is not metric, but rather 3/4” x 14 NPSM. Class 2B appears to be what you're after, from: Requirement to Gauge 3/4 NPSM - Scuba Engineer

The angle appears to be 50*-ish on the handiest tank I have nearby (an LP72), which is sort of weird. As it just forms part of the O-ring gland. I doubt it's terribly critical, but Parker wants 45* angles on triangular glands (p. 101 in my copy of the Parker O-Ring Handbook). The depth Parker wants 0.184" +/- .007" (p. 101, same reference). You should download the handbook and double-check before making chips, though. I'd certainly go with Parker before going with some of the slop I've seen in the scuba industry, but O-rings are amazingly tolerant seals.

HTH...

[Edit] Link to Parker's O-Ring Handbook: http://www.parker.com/Literature/O-Ring Division Literature/ORD 5700.pdf

 

[Nick Ruberg]

Thanks Trimix. It was actually the details of the chamfer which retains the o-ring (similar to the SAE ports which are the standard for the LP and HP fittings). I will do a straight counterbore which is a relatively easy to design and to dimension - I use that lots for hydraulic designs. Our cylinders here are all metric and so are my spare valves.