McMaster-Carr
This is probably known by all (except me until just now.) There's an Apeks document with a sizing chart contained within. Print it at 100% and verify with the handy scale at the bottom of the first page.
Apeks O-rings vs. McMaster
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This is probably known by all (except me until just now.) There's an Apeks document with a sizing chart contained within. Print it at 100% and verify with the handy scale at the bottom of the first page.
So we have @buddhasummer 's document that specifies 1.02mm x 2.8mm, and Scubagasket's 1mm x 2.5mm.
Both can't be right.
And then there's that picture with "actual size" silhouettes.
Guess I'll have to break open a kit.
Well, we have an answer of sorts.
The chart was printed at proper size (it actually took 99.5% scale on my printer to match out)
With that, the 5711 o-ring measured out at 2.8mm ID x 1.0mm C/S.
But when you put the kit oring on the chart, they sure don't look the same! But the ID matches the chart, so I can't complain. On the other hand, "stereoscopic camera" or not, that ain't a 2.5mm ID oring no matter what Scubagaskets says about 100% correct.
The oring in question is the balance chamber oring for the Egress (not one of their star regulators). See item #4 in the diagram. This oring is stretched over the post of the spring carrier #3.
But to ensure a proper seal in the balance chamber #6, I sure wouldn't use a 2.5mm ID without testing it! Using the formula Pi x ID for the circumference, you're stretching that o-ring almost 12%. That risks decreasing the cross- section diameter and not sealing to the balance chamber. Maybe it works, and maybe it doesn't, but this isn't the first time Scubagaskets has promoted a non-standard oring as a replacement. Caveat emptor. I'd be happy to be proven wrong.
In any case, it's a tempest in a teapot. It works or it doesn't, but I wouldn't be caught diving an Egress in the first place. Doesn't hold its tune, and the two halves of the valve assembly tend to lock together with verdigris corrosion unless you lube the valve halves heavily on assembly and you're religious about rinsing.
The chart was printed at proper size (it actually took 99.5% scale on my printer to match out)
With that, the 5711 o-ring measured out at 2.8mm ID x 1.0mm C/S.
But when you put the kit oring on the chart, they sure don't look the same! But the ID matches the chart, so I can't complain. On the other hand, "stereoscopic camera" or not, that ain't a 2.5mm ID oring no matter what Scubagaskets says about 100% correct.
The oring in question is the balance chamber oring for the Egress (not one of their star regulators). See item #4 in the diagram. This oring is stretched over the post of the spring carrier #3.
But to ensure a proper seal in the balance chamber #6, I sure wouldn't use a 2.5mm ID without testing it! Using the formula Pi x ID for the circumference, you're stretching that o-ring almost 12%. That risks decreasing the cross- section diameter and not sealing to the balance chamber. Maybe it works, and maybe it doesn't, but this isn't the first time Scubagaskets has promoted a non-standard oring as a replacement. Caveat emptor. I'd be happy to be proven wrong.
In any case, it's a tempest in a teapot. It works or it doesn't, but I wouldn't be caught diving an Egress in the first place. Doesn't hold its tune, and the two halves of the valve assembly tend to lock together with verdigris corrosion unless you lube the valve halves heavily on assembly and you're religious about rinsing.
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