How to Measure Neoprene O-Rings

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Neoprene o rings have a multitude of uses. They’re used in plumbing, cars, industrial machines, and even rockets. They are the most common type of seal used in the world.

If you need to replace an o-ring, you need to know the size to find the perfect replacement. If you don’t have a manual to find the right dimensions you’ll need to measure the old o-ring. This will get you the dimensions you require unless the o-ring is stretched out or damaged.

The first step is to lay the o-ring on a flat surface. Then use your measuring instrument to get the inner diameter. You’ll also need the cross-section or width of the rubber ring.

Once you have these two measurements you’re good to go. Most o-ring sizes are displayed as inner dimension x cross-section. For example, if the inner dimension is 10mm and the outer is 2mm, the size you need is 10mm x 2mm.

Sometimes you will also need the outer dimension. To find this, use the formula of inner dimension + (2 x cross-section). In the previous example, this would look like 10 + (2 x 2), so the outer dimension would be 14mm.

It’s a simple process, but one you need to ensure you get the right o-ring to properly seal the mechanism it’s used in. You can always talk to o-ring manufacturers if you need help finding it out.