Making working with O-rings easier

Making working with O-rings easier

Working with O-rings requires precision. There are numerous different materials and sizes available and not every O-ring is suitable for each application. It is therefore essential that you know which kind of rubber to use for your application and which dimensions are required.

Specific knowledge is also required when fitting and removing O-rings to ensure that they are used correctly. With this in mind, it is useful to know that there are various tools you can use to make working with O-rings that little bit easier. Read on to find out more about these essential tools.

Fitting and removing O-rings

Most of the time there is more to fitting and removing O-rings than you might initially think. Issues often arise when fitting and removing an O-ring due to the O-ring being in a hard-to-reach area or having small dimensions. Another problem that often occurs is O-rings breaking due to being fitted or removed incorrectly.

For this reason, it is essential that you use the correct tool. There are several tools at your disposal that make fitting and removing O-rings that little bit easier.

o-ring picker One such example is the O-ring picker. Standard O-ring pickers are made of plastic and are suitable for fitting O-rings in all manner of situations, even in the most hard-to-reach areas. There is also a tool set available that has been specially designed and compiled for work involving O-rings. The tools in this set are made of corrosion-resistant materials that are impervious to most liquids.

Determining the type of rubber

When an O-ring needs replacing, it is important to know which rubber material the existing O-ring is made from. There are several ways in which you can find this out. For example, you can look at the order history or contact an O-ring specialist. You can also use the rubber indicator to quickly get an idea of the type of rubber the O-ring is made from.

If you want to use the rubber indicator to help identify the type of rubber used, you will need to place a new or unused O-ring on a wooden surface. You will then need to place the rubber indicator in the centre of the O-ring cord. Next, pull the catch upwards and then drop it onto the cord. The number of times that the catch bounces up and down will provide an indication of the type of rubber used.

If the catch does not bounce, it is probably an FKM O-ring; if the catch bounces twice, it is probably an NBR O-ring; and if the catch bounces three times, it is probably an EPDM O-ring.

Please note! Using a used or deformed O-ring can provide a false impression of the type of rubber used. Furthermore, the result should only ever be considered to be indicative of the material used. For more information, contact an O-ring specialist.

Determining the size of a O-ring

In addition to determining the material that an O-ring is made from, it is also important to know the O-ring's size, as using the wrong size O-ring can result in leaks. There are various tools that you can use to determine the size of an O-ring.

These include Pi tape, the circometer and the O-ring gauge. As previously, you will obtain the most accurate results by measuring a new O-ring. You can find details about all three tools below.

pi tape

Pi tape
You can use Pi tape to find out the inner diameter of an O-ring. Pi Tape is double-sided, with both sides serving different functions. One side can be used to determine the inner diameter of an O-ring in millimetres, within a measuring range of 50–345 mm. This side of the Pi tape can also be used to measure the cord thickness in metric sizes.

The other side of the Pi tape can be used to determine the inner diameter of an O-ring in inches, based on the AS size. You can also use this side to measure the cord thickness in inches.


You can use a circometer to determine the circumference and diameter of an O-ring. This is accurate up to one-tenth of a millimetre. There are seven types of circometer, each with a different measuring range.

Once you have measured the circumference and diameter of an O-ring, you can then use the following equation to determine its inner diameter:

Inner diameter = circumference of the O-ring / π (3.1415) - 2 x the cord thickness of the O-ring

o-ring gauge

O-ring gauge
In addition to the Pi tape and the circometer, you can also use the O-ring gauge to measure O-rings according to the AS 568A standard. This measuring tool indicates which AS size an O-ring corresponds to using three numbers.

If you are looking for more information on these essential tools or have any questions, please don't hesitate to contact us. Our specialists are ready to help.

auxiliary tools for O-rings