O-rings must be a strong contender for being the most useful and widely used component in industry. They are used in almost every engine, appliance, motor and hydraulic system. There are thousands of types of different O-rings, made from six principal materials and available in a wide range of sizes.
For an O-ring to be effective it has to be sized precisely to fit your appliance. Fortunately, there are O-rings commercially available to suit every possible use. However, you do need to make sure you choose the right size. This article explains how rubber O-ring sizes work and how to avoid choosing the wrong component.
Rubber O-Ring Sizes
Fortunately for everyone involved, O-ring sizes are standardised according to the ISO3601 numbering catalogue, which makes them easy to order if you know what you’re looking for. The catalogue number refers to the size of the O-ring, so to place an order with a company such as ourselves, we only need the following information:
a) ISO 3601 catalogue number (Internal Diameter size)
b) Durometer (measure of hardness), material and colour
c) Order quantity
d) Cross-section (if known)
Catalogue numbers are assigned based on an O-ring’s inside diameter (ID) in ascending decimal numbers from smallest to largest. The smallest available O-ring has an inside diameter of 0.74 mm and the largest has an ID of 658.88mm, so there are plenty of options to choose from! O-rings also have varying outer diameters (OD) and cross-section measurements, which are frequently given in catalogues, although these are not strictly relevant when ordering by size.
What Mistakes To Avoid
The 11 digit ISO 3601 catalogue numbers are extremely well organised but there are still a couple of common mistakes that people make when ordering. Here are the most common:
1) Getting The ID Catalogue Number Wrong
With thousands of components to choose from it is easy to order the wrong type of O-ring in error. At BSCL we provide our customers with detailed product knowledge and telephone support should you need it, so if in doubt please give us a call and we’ll make sure you find the right part.
2) Not Adjusting For Shrinkage
The standard O-ring sizes are based on components made of 70 durometer nitrile rubber. Other materials experience different levels of shrinkage during the moulding process, which can affect the actual size of the component. You may therefore order the right size for your application, but because shrinkage is not taken into account, the part turns out to be too small. This is one of the reasons we request the hardness and material as part of the sizing and ordering process. It rules out the chance of ordering the wrong size. For more information on identifying the right material, please consult one of our technical sales team.
3) Ordering By Outside Diameter
O-rings are ordered according to internal diameter size. A common issue is to mistake the catalogue numbers as referring to outside diameter, and so order the wrong part.
O-Ring Ordering Made Easy
There is nothing more frustrating than ordering the wrong component, which is why at BSCL our aim is to give you all the support you need to get the right parts. We do provide documentation and charts on request, but we also realise that not all of our customers will automatically know what part they are looking for. So if in any doubt, give us a call and we’ll talk you through the process and ensure you get the right parts, first time round. We keep thousands of product lines in stock for fast delivery to any address in the UK.
The Buyer’s Guide To Industrial O-Rings
More information about O-rings and hydraulic seals can be found in our new Buyers Guide to Industrial O-rings. This free resource explains how different O-rings are used, how they are made and how to select them for their required characteristics. Click here to download your copy.