Pro/Forums - o-rings

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How big a groove do you need for an o-ring.

Would 1mm deep be sufficient?

How wide would it heve to be? would 2mm be enough or would you need 2.5, to go with the depth of 1mm.

8-ball

It all depends on what O-ring you choose.

There are numerous books on the correct use of O-rings. Pretty much any metak-working machine-shop will have such documents handy. Other than that, Google is your friend.

you want some compression and a good fitting. I'm doing mine with 1/8" dia o-ring material because i have about 500 yards laying around and dont have any 1/16" :P anyway i'm doing a 1/16" on the bottom plate and a 1/32 cut on top so there is a bit of compression. but go with what your o-ring material asks for, all are different.

Quote:

Originally posted by chewyboy
...but go with what your o-ring material asks for, all are different.

Really? That's not what I read...

I'll be using a 1/16 o-ring, in Radius. BillA posted some excellent specs, based on his years of experience:

Quote:

after designing and doing failure analysis of o-ring joints for many years (in both static and cyclic pressure service),
there are several useful guidlines:
- when the component surfaces make contact, as they must, there should be 30 to 40% compression of the crossection
- the o-ring's volume should be between 60 and 70% of the groove's
- using a 30 to 50 Shore A durometer (hardness) material will make the surface finish less critical
- the o-ring's (centerline) length should match the groove's (do NOT stretch)
- the groove must have an outer containment ring to 'capture' the o-ring, else it is functioning as a gasket (different design basis)

do not use a sealant with the o-ring (no need if properly designed, will overfill the groove, make disassembly a pain, etc)

If you need any help, let me know.

I'll admit he is an expert i've only used it for maybe 10 projects (which by no means makes me an expert) but from my experience go with what the o-ring manufacturer calls for. they all are different. some are harder rubber that do not like compression as much and some are softer and like more compression. so yeah i am disagreeing with him a little bit :P but not enough to start a flame war.

...and I've never used it, but my readings indicate a 20% height compression. (gotta find my print-outs...)

Since the materials have a durometer rating, I had a hard time understanding your statement, but it makes sense now.

I've opted for silicone, as a material, because it's cheap, and will resist the chemicals I'll have in the coolant. Bill suggested EPDM, but that first price quote scared me off of it. It's actually cheaper than I thought.

www.efunda.com is your friend when it comes to this. It's quite possibly one of the best engineering reference sites available.