Measuring O-rings

[RvL04]

Hi!

Does anybody have any experience measuring the (inner) diameter of rubber O-rings? What's the best method? I've read about cone gauges (both stepwise and smooth) and they look helpful, but I'm just wondering if I'm perhaps overlooking an obvious option. Currently, I'm just using calipers, and that's far from accurate.

And what about the thickness / outer diameter of the O-ring. At least calipers work better for that, but perhaps there is something that does better at this also?

O-rings in question tend to have a I.D. between 5mm and 80mm, and a thickness between 0.1 and 5mm.

Thanks!

 

[ejc]

There is no good way that I have found for measuring these o-rings. The best thing, for small sizes is the cone gauges that manufacturers can supply. These may not tell you the exact inner diameter, but they will at least let you know if the rings are in spec. Try Parker o-ring division, they can offer some other suggestions or at the very least, supply you with a measuring cone.

 

[eth]

Consider using an optical comparator if you have access to one. For o-ring measurements a vertical beam would be more convenient but if all you have is a horizontal comparator, simply glue the o-ring to a piece of glass and place the glass in a vise. Compensate for any out of round condition by averaging measurements that are 90° apart.