O-rings... not dirty.

[Lance_Wallen]

as my of my posts have stated, I'm working on some projects. The latest little issue is determining what size o-rings to use for my rba tanks. I"m getting pyrex tubing with a 3/4id and 1"OD. I'm going to be using o-rings to secure it. I'm thinking 1/16th width rings but I'm not real sure what OD i should be looking for. Should I go 3/4 OD and cut my groove to be slightly larger than the ID of the O-ring so it stretches it and then uses the rest of the excess as compression or will a 3/4OD O-ring not make a seal at all with a 3/4 ID tube around it?

would a 13/16th OD O-ring be 'too' much O-ring and cause the seal to be too tight/impossible to put on? I'm not sure how much compression I can expect here and I don't want to waste too much material screwing up.

THanks in advance.

 

[asdaq]

The first option sounds better. I think you are going at this by mathematical precision, I go by feel of the fit. You can get o-rings in all sorts of sizes, so having several sizes in the ballpark would be a good idea. Also, stretching them on is a good thing, that way they don't fall off. For example, I've been using 10/1mm (ID/thickness) and cutting grooves good for that size, but found they can slip off too easily. Stretching a 6/1.5mm o-ring on the same groove is harder to get on, but gives a nice stability to holding on the mouthpiece and doesn't slip off.