O Ring Kits

I’ve needed a number of different O Rings recently and without exception they’ve all had a 2mm C/S. I’ve got a couple of small boxes of mixed sizes and they’re all 1.5mm, 2.5mm or larger C/S! I have looked at other kits on the market and they all seem to omit 2mm. I’ve ordered what I need now from a supplier on the auction site and just in case I’ve ordered a few other sizes in the same C/S. anyone else come across this anomaly?!

Yeah had the same problem myself late last year, thank goodness for eBay. I managed to get all I needed plus pares plus a few extra sizes just in case.

For what the kits cost (£ 12) I bought both imperial and metric, gives me a huge choice of sizes and section. Then a few yards of various size cord and a pot of superglue and you can make your own. Noel.

I needed another size, once more not in any kits that I’ve seen - 12mm OD x 1.5 CS. Do the people that make up these kits do it on purpose?!
I’m so glad I didn’t lay out ten or fifteen quid for one of these kits as they never seem to have the size I need.

I use a fair number of O-rings is stuff that I design and make yet very rarely use an O-ring out of either the metric and imperial kits I have. Two reasons really, one is the seal material which is a bit of an unknown quality, secondly is whilst a kits look to cover a range of sizes, in reality its is a fraction of the standard size range.

I sometimes need to seal 1.5mm (and sometimes smaller) control spindles, and up to 250mm diameter bayonet joints so well outside what kits contain. For underwater use my preference is silicone rubber.

Ian P

In case anyone does not know. O rings are sized by Inside diameter and cross section. ie 18 x 3's are 24mm OD withh 3mm cross section. If you order 18mm x 3mm O ring what you actually get is an 24mm OD x 3mm CS. So when ordering make sure you order correctly.

regards

Not wishing to teach anyone to suck eggs, Imperial "O" rings are sized by ID x OD as opposed to the metric sizing above.

Mick

Then there are several different materials, nitrile, Viton, silicone, Etc and a hardness - The shore number. 70 is normal. Noel

The Metric ones I’ve been getting from a specialist on eBay are clearly marked ID x CS. I think they even have a diagram for the hard of understanding!

For the sake of clarity and avoidance of confusion

O-rings whether metric or imperial are referred to by the inside diameter followed by cross section

Ian P

Ah yes:

"Teach not thy parent's mother to extract /The embryonic juices of an egg by suction./That worthy lady can herself enact,/Quite irrespective of thy kind instruction." Boy's Own Paper, April 29, 1882.

The problem I have found with O-ring kits (along with other kits in compartmented plastic trays) is that they seldom list the dimensions of the parts in the compartments.

George

I also have one of those O ring boxes, and it only rarely has the required item. Add in extra complication of material specs such as viton for higher temperatures then its a no brainer. Auction site all the way.

Martin

Obviously not as cheap as buying a plastic box of assorted sizes at Lidl but the prices I’ve seen so far on eBay don’t seem too bad. Strangely though I only seem to see one vendor on there. Perhaps my search term isn’t wide enough?! Service from them so far has been pretty good.