Replacement O rings

[bert]

Is there by any chance a simple rule of thumb for calculating the required size of a replacement o ring? I l looked up a supplier and they had a chart which seemed horribly complicated.

[fred]

Try ebay for an 'O' ring set. You'll get a selectiob for very little money

[Martin Brown]

The dimensions of the one that you are trying to replace?

[newshound]

True but IME they normally contain "thinner" rings and often don't have a good match for existing ones.

If you are missing the ring altogether, your replacement should have a bore close to the depth of the groove (slightly loose is OK), a thickness close to the width of the groove, and it should stick out slightly when it is in position.

They normally come in integral metric sizes, if you see what I mean. (Same applies to imperial).

[Andy Burns]

I find pressure washers need sizes that are not in the selection boxes, and they're picky to 0.1mm, too small leaks, too big refuses to connect.

[alan_m]

You get a selection but often when you need one you find that they are too thin. Although I have found a use for many in a set its always one or two sizes that are used most.

Inside and outside diameter are the important parameters, assuming a round cross section of the ring

[Dave Liquorice]

I think you need both metric and imperial sets to be covered.

I find that with all O rings, which is where having the two sets is useful. 6mm v 1/4" sort of thing...

[Fredxx]

There may well be charts but I have gone by diameter and thickness as being the two defining measurements.

[newshound]

Correct, two dimensions and the material are the only parameters. OD follows from ID and thickness/cross section. The latter is sometimes called "chord".