ABEC Rating: A Tool in Bearing Selection

Are you worried that your application requires more precision than a standard bearing can provide? Understanding ABEC ratings and how they may affect your application is a good way to start. For example, ABEC ratings do not provide specifications for performance criteria such as limiting speed, radial and axial loads, and noise. However, ABEC ratings and a bearing’s precision are directly correlated. 

Being knowledgeable about ABEC ratings and how to use them as a tool to select bearings for your applications will save you time and money. Choosing a bearing with the correct precision for your application can prevent you from overpaying. Conversely, knowing when your application will need a high-precision bearing will give the performance needed.

What is ABEC Rating?

ABEC rating is a scaling system used to measure the tolerances and thus precision of bearings in a specified class. They have become the industry standard for ball and roller bearing tolerances. In fact, bearing manufacturers are required to have their products rated by ABEC.

The ABEC scale is designed to provide bearing manufacturers with dimensional specifications and tolerances that meet the standards of precision bearings. ABEC ratings are used as one of several tools in the process of deciding which bearings are best for the application. 

ABEC standards were developed by ABMA which is a subset of ANSI. The three are dissected in the table below.

ANSI	American National Standards Institute: Facilitates and coordinates the U.S. voluntary standards and conformity assessment system Standards for any industry
ABMA	American Bearing Manufacturers Association: Works as a subset of ANSI to develop and publish Bearing Industry standards
ABEC	Annular Bearing Engineering Committee: A subsect of ABMA that focuses on dimensional tolerances and running accuracy

What do the ABEC Numbers Mean?

The ABEC rating scale ranges from 1 to 9 using odd numbers. Higher numbers indicate greater precision and tighter manufacturing tolerances. Lower numbers indicate slightly less precision and looser manufacturing tolerances. It should be noted that a higher ABEC rating doesn’t necessarily mean higher speed. The rotational speed is also dependent on several other factors.

Here is a breakdown of the ABEC scale ratings:

Commercial Grade (no ABEC rating)	Tolerances that fall outside of any ABEC rating. May exhibit more wobble and vibration due to a lack of precision honing. Typically found in commercial applications such as drawers and toys.
ABEC 1	Bearings with a level of precision that is acceptable in ~90% of industrial applications. Typically found in automotive components, electric motors, gearboxes, and other industrial machinery. May not be truly tested and certified by ABEC. Thus ABEC 1 is the default rating for the majority of precision bearings.
ABEC 3	Tested and certified, these bearings offer a higher level of precision and better quality components. They offer reduced friction and improved output. Typically found in higher precision industrial components like high-quality electric motors.
ABEC 5	Provides even tighter tolerances and higher quality output for more specialized applications. Used in industrial applications such as high precision planers that require the smoothest quality output to avoid flaws in manufactured products.
ABEC 7	Bearings with a high level of precision and tighter tolerances. They are often used in high performance applications such as high-speed routers and robotics.
ABEC 9	The highest rating on the ABEC scale, representing bearings with extremely tight tolerances and exceptional precision. Typically used in specialized applications with continuous operating speeds of 10,000 RPMs or higher or demanding requirements such as aerospace.

The ABEC rating primarily measures the dimensional precision of the bearings but may not fully reflect other important factors like material quality or design features that can affect overall performance. For specific applications, it’s essential to consider factors beyond the ABEC rating to ensure the bearings meet the necessary requirements.

Now that we are familiar with ABEC ratings and what they mean, it is important to understand the terms dimensional tolerances and nominal dimensions when selecting a bearing.

What are Nominal Dimensions?

In the bearing industry, a nominal dimension is the requested ideal measurement. However, because nominal dimensions are usually quite precise, engineers will need to determine the amount of dimensional tolerance that is acceptable for their application.

What is Dimensional Tolerance?

The dimensional tolerance is a range of allowable measurements outside of the desired nominal dimension. For instance, if an engineer requests an inside diameter of 20.000mm the ABEC rating of the bearing will specify the amount of deviation is acceptable. A higher ABEC rating means the measurement MUST be closer to nominal than a lower ABEC rating.

ABEC standards outline what those tolerances should look like in order to achieve certain ratings. They look at the size of the bearing to determine overall ABEC ratings.

How to Use ABEC Ratings to Choose Bearings for Your Application

Using ABEC ratings to select the right bearing for your bearing application requires an understanding of what the ABEC scale represents. It is important to note that while ABEC ratings can be helpful in determining a bearing that will ensure the application performance, several other factors need to be assessed when selecting a bearing. The ABEC scale does not take material properties, impact resistance, side loading, lubrication, clearance, noise, and installation requirements into consideration.

A vast majority of bearings sold fall between ABEC 1 and ABEC 3 on the scale. These bearings fall somewhere in the lower/ middle of the spectrum and are commonly found in standard-precision applications such as automotive components, electric motors, and gear boxes.

ABEC 5 bearings are built for high speed and high running accuracy. These bearings have the same nominal external dimensions as equivalent size ABEC 1 grade bearings, but running characteristics and external dimensions are held to closer tolerances. 

Bearings with an ABEC rating of 7 or 9 are typically required in applications with VERY high RPMs and / or VERY high running accuracy. Manufacturing these higher-rated bearings requires more precise machining and extended production time. This often results in a significantly higher price point. This cost increase can sometimes be five to ten times more than standard-precision bearings.

Tighter tolerances are typically required in applications where bearings need to function at very high RPMs or in equipment demanding highly accurate positioning. 

It is possible to observe a significant difference in performance between two similarly rated bearings in different environments. Likewise, it is entirely possible for bearings with lower ABEC ratings to perform equally to higher rated ABEC bearings in specific applications.

Conclusion

To select the right bearings for optimal application performance you need to know whether or not your industrial application requires more-than-standard precision. The ABEC rating provides a standardized system for assessing bearing precision and quality. By considering factors such as dimensional tolerance and nominal dimensions, ABEC ratings offer valuable insights into the output performance characteristics of bearings.

Remember, while ABEC ratings are a helpful guideline, there are several other factors to consider beyond these ratings to ensure the bearings meet the specific requirements of your application. Combining an understanding of ABEC ratings with a detailed approach to bearing selection, you can enhance output quality, efficiency, and reliability in your applications.

Bearing tolerance standards create consistency in the industry and in manufacturing to ensure a uniform product. Knowing how to reference ABEC ratings allows you to make informed decisions about the types of bearings that are best for your application. The right bearing choice ensures the output performance of the application and it also saves the design budget.