O-ring size help

[guruboy]

trying to identify an o-ring size
(xDeep stealth o-ring)

Actual measurements-
5/16 thick
2" OD
1.5" ID

Seems like a 401 but the 401 isn't thick enough.

 

[tursiops]

At least one of your numbers is wrong. The ID plus twice the thickness should equal the OD, although the "thickness" is a nominal description and not necessarily the actual diameter. For example, see Oring Size Chart where the nominal 1/4-inch rings (the 400 series) are described as "actual 0.275" inches, which would be within 13% of your 5/16 measurement.

If you are wanting it to replace the rubber o-rings on the Stealth, then the durometer is also important.

Many folks are using the 323-90D rings; about $0.35 each for a package of 25, including shipping. they seem to work fine, although my next buy will be the 400 series, probably the 401, in fact.

I actually have both the stealth and the 323 o-rings in front of me right now. The 323 is usable for some other things, like sticking through an ULCS strobe arm to attach a small shackle.

 

[guruboy]

I used a digital caliper and measured multiple rings.

The ID is slightly less than 1.5 but pretty close though. It's possible the OD is just slightly larger than 2. Either one would only be fractions of an inch off though, 1/16 or less.

The thickness I am measuring as the cross sectional diameter of the o-ring. Not sure if there is a different way I'm supposed to do it.


Overall the 401 will probably be close enough (or the same). What durometer are you using? I was going to use 70.

 

[tursiops]

Overall the 401 will probably be close enough (or the same). What durometer are you using? I was going to use 70.

I agree. Close enough.
The 323 is 90. I don't know what the Stealth ring is but it "feels" like 90 or maybe 70. I think 70 would be fine for the 401 because its thickness gives it some resilience to squeezing. You don't want the o-ring to be floppy! Better a bit stiff than a bit floppy.

 

[Pao]

It is a European product, have you tried matching it with a metric O-ring? Or better yet, get the sliding D-rings from Sump UK. Some people seem to like the LB-SR by Santiago diving but they seem to be as rare as unicorn tears :-D

 

[guruboy]

Hard to find EPDM in 90 though

 

[guruboy]

This page lists them as 50mm OD 5mm thick.
XDeep Stealth Sidemount System, O-Ring – Rubber

Seems a little thinner than what I measured (5mm is closer to 0.20")

 

[tursiops]

This page lists them as 50mm OD 5mm thick.
XDeep Stealth Sidemount System, O-Ring – Rubber

Seems a little thinner than what I measured (5mm is closer to 0.20")

?? the page linked says 5cm diameter, and later 50mm diameter. That is the same.
I see nothing about thickness of 5mm.

50mm diameter (outside? inside? middle?) would be 1.97 inches, which is essentially the 2-inch OD that you have previously measured.

 

[guruboy]

good catch. I misread 5cm as 5mm.