Understand bearing nomenclature

🔗 Mechanical transmission

Date of publication : 07/06/2023

Reading time : 4 Minutes


Explore the importance of bearings in reducing friction and facilitating the rotary movement of mechanical parts.

Bearings are essential elements used in many machines and devices to facilitate the rotary movement of parts. They are designed to reduce friction and support high loads while providing smooth movement. The nomenclature of bearings is based on different criteria, such as dimensions, performance characteristics and specific designs.

This allows manufacturers to be able to innovate freely to differentiate themselves from other producers, while ensuring the interchangeability of bearings and the profitability of production.

By understanding bearing nomenclature and their equivalents, you will be able to choose the appropriate bearings for your needs, compare products of different lubricant manufacturers lubricants and guarantee optimum performance in your mechanical applications.

How to choose a bearing ?

The choice of this product is generally conditioned by the dimensions, speed And the charges that he has to bear. These constraints depend on the assembly of the machine.

  • Dimension: The dimension of a bearing refers to its geometric characteristics such as inside diameter, outside diameter and width. These measurements are usually standardized and should match the dimensions of the application in which the bearing will be used.
  • Speed: Speed ​​is the maximum rotational speed at which a bearing can operate without suffering excessive damage. It is usually expressed in terms of revolutions per minute (rpm) or radians per second (rad/s). The reference speed for a bearing is often stated by the manufacturer and must be adhered to to avoid premature bearing failure.
  • Load: Load refers to the force exerted on the bearing during its operation. It can be classified into two main categories: radial load and axial load. Radial load acts perpendicular to the axis of rotation, while axial load acts in the direction of the axis

Decoding bearing designations

The designation of a ball bearing is more than just a reference number. It contains a set of bearing data. In this article, we explain how to decipher the three main characteristics of the product in the designation. Improve your expertise in minutes!

The bearing designation system

The nomenclature of bearings consists of numbers, sometimes supplemented with letters. Prefixes and suffixes indicate different characteristics of the bearing. Manufacturers tend to use different suffixes and prefixes for similar features. A list is therefore necessary to understand its meaning. The link below will allow you to understand the different suffixes according to the main brands.

The basic designation is designed logically. “Basic nomenclature” means the codewithout prefix or suffix. The basic nomenclature is composed according to principles respected by a large number of manufacturers. We will see how to easily decipher several important data.

Part 1: Types of bearings

The basic designation itself has three fixed components. The first part is a number, a letter, or a combination of both. It designates the type of bearing.

   Double row spherical roller bearing 1
   Spherical roller bearing 2
   Single Row Tapered Roller Bearing 3
   Double row deep groove ball bearing 4
   Thrust ball bearings, single or double acting 5
   Single row deep groove ball bearing 6
   Single row angular contact ball bearing 7
   Cylindrical roller thrust bearing 8
   Single row cylindrical roller bearing N
   Four point contact ball bearings QJ

Part 2: The bearing size series

This has a first digit (sometimes omitted) which gives the width (of a radial bearing) or the height (of an axial bearing). The second number in the dimension series indicates the outside diameter.

The radial bearing supports radial loads, therefore perpendicular to the axis; the axial bearing supports axial loads, in the extension of the axis.

This part of the basic designation designates the dimension series.

Dimension Series Organization

The higher the value, the thicker the inner and outer rings. Often, the size of the beads also increases. Bearings for which this value is higher therefore support higher loads.

In our first example, the 6203DDUC bearing, the dimension series is "2". The table shows that this is a medium-width class. In our second example, the 7410BMGN bearing, the dimension series is "4". This bearing will therefore support (relatively) higher loads.

Part 3: The Inside Diameter, or Bore

The third part indicates the inside diameter, in other words the bore. These are the last two digits of the basic designation. A simple calculation makes it possible to deduce the bore.

A typical bearing base designation therefore looks like this: A BC DE

  • A – Type of bearing
  • B - Width
  • C – Outer Diameter
  • DE – Bore diameter

This part of the basic designation designates the bore.

Is the number equal to or greater than 04? Multiply it by 5 to get the inside diameter (in mm). Easy as pie. There is, however, one inevitable exception. If the number is less than 03, the bores are as follows :

Bore Diameter 10mm 12mm 15mm 17mm
Code 00 01 02 03


In practice

Finally, let's take one last example. Let's say your customer calls to request a 21317-E1-K from FAG. Applying what we have just explained, you can reply to him: "Just a moment please, I'm checking to see if we have your spherical roller bearing with 85 mm bore in stock, or offer him the equivalence in NSK with the 21317EAKE4N.First read in this bearing guide the basics to recommend a bearing:The nomenclature of bearings.

Principle of Equivalence - Bearings

In this article, we will tell you about the principle of equivalence, allowing you to find an interchangeable product if your reference is not available in stock? Or when you would like a bearing from a different brand?

However, it can be very difficult to determine which bearings can replace others. We will see how to facilitate this search.

What are "equivalents"?

"Equivalents" are bearings of different brands that have the same dimensions and characteristics. These bearings can therefore be used under the same conditions. The "equivalents" therefore allow greater versatility and greater independence of choice. So if a certain type of bearing is not in stock, you can still provide a solution to your customer. Or maybe you want to offer a cheaper brand to change? But how do you know which bearings are interchangeable ?

We will first look at the serial numbers of the parts, helping to identify the BOM of the bearing. The full serial number of a bearing consists of the product designation to which prefixes or suffixes may be added. The designation refers to the series and the bore. In principle, most bearings use the same designations, with a few exceptions. This is a standard nomenclature that contains important information. If you understand their meaning.

Bearing Part Number Breakdown

Bearing prefixes and suffixes

However, this logic does not always apply to prefixes and suffixes. Sometimes manufacturers use their own codes which appear to have been randomly assigned. It happens that some of these codes are shared between different brands to designate the same characteristics. However, this is not the case for everyone.

We can take the example of suffixes to designate a bearing with two rubber seals, depending on the brands it may be designated by the terms 2R, 2RS1, 2RSR, LLU of the EE. These indications can be quite abstract if you don't know what they mean.

How do I find the suitable equivalent ?

The list below will help you better understand inter-brand equivalences.

Equivalents can be found on the Online store ITAFRAN in two ways. The first is to refer to the product sheet.

You can also identify equivalents using the catalog page filters and the search bar.

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