A Complete Guide To Ball Bearing Measurement, Bearing Sizes And Bearing Codes

Ball bearings are essential components in many mechanical systems, including vehicles, industrial machinery, and household appliances. They help reduce friction and allow for smooth movement between two surfaces. Selecting the correct ball bearing is vital for various reasons, as it directly affects the performance, efficiency, safety, and potential downtime of a wide range of machines and equipment. To ensure proper functioning, it is important to know the type and size of a ball bearing.

This guide aims to assist, you the customer in measuring ball bearings accurately to make sure you select the correct bearing for your specific application. Proper measurement is crucial in identifying the appropriate ball bearing size and type, as well as interpreting bearing codes to make an informed choice. Let’s go through the step-by-step process of measuring a ball bearing and understanding bearing codes.

Before measuring, it’s important to identify the type of ball bearing you have. There are several common types, such as deep groove ball bearings, angular contact ball bearings, and thrust ball bearings to mention a few. Each type has its own unique design, and it is essential to recognize the correct type you have for accurate measurements. For more information on the different types of ball bearings available please see our Ball Bearings Guide

Ball bearings usually have their identification code stamped or lasered on the outside diameter of the bearing itself, using this is the best way to ensure you select the right bearing.

However, over time this code can become illegible or possibly worn away. So, it is important to be able to measure a ball bearing correctly.

Determining the size of a ball bearing can be done by measuring its outer diameter (OD), bore size (ID), and width. These measurements are usually expressed in millimetres (mm). Using a calliper or a micrometer, you can accurately measure these dimensions.

Tools you’ll need

1. Calliper or Micrometer (digital or manual)
2. Notepad and pen for recording data
3. Flat and clean surface for measurement

So, what does the code on your bearing actually signify? Let’s dig a little deeper and explain in a bit more detail.

Typically bearing codes are comprised of a ‘basic number’ and depending on the bearing they can have supplementary codes at the beginning or the end of the basic number. These are the prefix and suffix codes.

The basic number will give you general information about the bearing such as the type, series number and bore size.

We will use a popular bearing (S) (6001) (2RS) as our example

Start by breaking down the code on your bearing into 3 parts

1. S (prefix)
2. 6001 (basic number)
3. 2RS (suffix)

Prefix

Bearings very rarely have a prefix code. However, you may come across one that does. The prefix is used to highlight the parts used by the manufacturer in the design of the bearing. In our example where we have a Prefix of (S) it tells us that the bearing was made using stainless steel. Below are a couple of common examples

Basic Number First Digit

The first digit of the basic number tells you about the type of bearing you have. In our example, it’s (6) So this tells us it’s a Single row deep groove ball bearing.

Basic Number Second Digit

The second digit of the basic number tells us what series the bearing is from and is used to signify how tough the bearing is. In our example, it’s (0) Which tells us its extra light toughness.

Basic Number Third And Fourth Digit

The third and fourth digits tell you the bore size or (ID) of the bearing you have. In our example, it’s (0) which tells us the bearing has a 12 mm bore size.

Important Note that from 20mm and above you would need to times (x) the last 2 digits by 5 to ascertain the bore size for nearly all types of bearing.

Suffix

Suffixes indicate bearings with additional special characteristics or designs. They are typically used to provide information about how the bearing is sealed. In our example, it’s (2RS) which tells us our bearing is sealed on both sides.

Clearance Codes

In some cases, your bearing may have an additional suffix such as C3. This can be found on the outside diameter of the bearing except in the case of CN. This refers to the bearings clearance code. See the table below for examples.

It is important to note that different manufacturers can have their own specific Prefix and Suffix codes. Our tables give you some examples of the most common codes. If in doubt please check with the manufacturer of your bearing for exact information.

So now you have a better understanding of how to measure a ball bearing and how to interpret a bearing code, why not check out our great range of high-quality bearings from industry-leading brands such as SKF, NSK, FAG, INA and of course our own brand RS PRO.

We have created a list of the most popular sizes to make it quicker and easier for you to identify and purchase the exact ball bearing for your application. Simply click on your size and view our current selection.

In conclusion, mastering the art of measuring ball bearings and understanding bearing codes is vital for anyone involved in mechanical or industrial applications. By following the steps outlined in this guide, you can confidently and accurately determine crucial parameters like inner and outer diameters, width, and radial play.

Furthermore, decoding bearing designations enables you to select the right bearing for your specific needs, optimizing performance and longevity. Remember that precision is paramount, and a well-measured bearing is essential for efficient machinery and reliable operation.