Bearing Tolerance Standards
Bearing tolerance standards create consistency in the industry and in manufacturing to ensure a uniform product.
Bearing Precision Class Ratings
Internationally, the International Standards Organization (ISO) is used for specific boundary dimension tolerances in rolling bearings.
In the United States, the American National Standards Institute (ANSI) oversees standards and conformity systems. The Annular Bearing Engineering Committee (ABEC) is an industry-accepted standard for the tolerances of a ball bearing.
For European standards, you’ll commonly see Deutsches Institut für Normung (DIN) represented.
See how each standard compares in the table below:
|ANSI Standard*||DIN 620*||ISO 492*|
|ABEC 1||P0||Class Normal|
|ABEC 3||P6||Class 6|
|ABEC 5||P5||Class 5|
|ABEC 7||P4||Class 4|
|ABEC 9||P2||Class 2|
*The chamfer and other dimensions may be supported by other standards.
Please note: Some bearing manufacturers have created their own customized and branded tolerance standards (like P4+), in this article we’re only focusing on internationally recognized standards.
The Process for Bearing Standards
These standards are created and overseen by ABEC, a group under ABMA.
ABEC and ABMA carry the weight of the industry and are the primary caretakers of bearing tolerancing in the United States.
All the bearing standards organizations, including DIN and ISO, work together for a common goal of creating equivalent bearing tolerances worldwide. This goal is achieved when users can trust in the bearing standards and are able to successfully use precision bearings uniformly across many industries around the world.
How to Understand Precision Bearing Classes
For ABEC precision classes, the higher the ABEC number the tighter tolerance of the manufactured bearing. Here is the ABEC scale in order from loose to tight: ABEC 1, ABEC 3, ABEC 5, ABEC 7, and ABEC 9.
However, the DIN and ISO classes are opposite of the ABEC scale. The higher the number the looser the tolerance. Here is the DIN & ISO 492 scale from loose to tight, respectively: P0, P6, P5, P4, P3, and P2. And ISO 492: Class Normal, Class 6, Class 5, Class 4, Class 2.
What’s Included in the Bearing Tolerance Standards?
Precision bearing tolerance classes include standards for form, fit, function, and correlated running characteristics of bearings.
This includes but is not limited to:
- Inner Diameter
- Outer Diameter
- Radial Runout
- Face Runout
- Axial Runout
- Profile of a Surface
- And more
Are Bearing Precision Classes Really Important?
Here’s an interesting tidbit regarding bearing precision classes vs. running capabilities: Every bearing has the potential to hit the same maximum RPM. The difference is: What percent of the time does this maximum RPM need to be reached during operation?
Pricing & Budgeting for Precision Bearings
There are usually large jumps in pricing when you go from an ABEC 3 to an ABEC 5, and then again from an ABEC 5 to an ABEC 7.
When precision machining of bearings was just starting, only ABEC 1 bearings were consistently produced. As machining expertise and technology increased, so did the consistency and reliability. Now, ABEC 7 and ABEC 9 bearings are produced relatively easily.
The greater the need for reliability, runout, RPM, etc. the more the cost is justified for a higher precision bearing.
Low Precision Bearings Can Be a Gamble
If you’re designing an application that has a tight tolerance requirement and rotates at fast speeds with high reliability placed on it, then you probably don’t want to gamble with a low precision bearing.
As an application reaches higher and higher RPM’s, every micron of parallelism, runout, surface profile, etc. all make a difference.
To consistently run an application at high speeds, a precision bearing in an ABEC 7 class or higher is most certainly recommended.
Precision Standards Aid in Engineering
For example, our Standards and RPM calculator uses ABEC tolerancing standards to map the dimensions needed for the shaft and housing.
If you need help with your tolerancing strategy, contact us and one of our engineers would be happy to help.
Why Buy From GMN Bearing USA?
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- Rapid Response: 99% of inquiries are responded to within one business day and most orders ship out the same day (from Houston, Texas).
- Expert-Level Support: Our onsite mechanical engineers and technical support specialists provide answers to your most difficult questions.
- Quality 360°: Our internal quality control process is one of the highest in the industry. We make sure GMN is synonymous with quality.
Need help finding the right product for your application? Contact us today.