Ball Sizes Within Our Precision Bearings

There are multiple aspects of any bearing company that will result in various ball sizes per bearing design series, size series, and specific OEM design decisions.  These decisions will change load ratings and RPM ratings of each individual bearing size or selection. GMN Bearing USA is here to explain the various ball sizes within our ball bearing series.

Angular Contact Bearing Ball Sizes

First and foremost, GMN has 3 primary design series for our Angular Contact Bearing offerings; S Series, SM, and KH Series.

The S and SM Series are considered ‘large’ ball by most people within the industry.  The SM will have a higher RPM rating than the S, but the S will have a larger load capacity than the SM.  These were internal engineering decisions by GMN to offer an SM type with a higher speed rating based on bearing design.  The S series would be considered a standard or common Angular Contact Bearing design that is easily interchangeable with competitors, although other series may be easily interchangeable as well. 

The KH series was intentionally designed as a ‘small’ ball design to optimize for higher speed applications. 

Universal Bearing Sizes

The size of the bearing series then comes into play. These series are universal across all of the bearing industry. From smallest to largest; 800, 900, 1000, 200.  There are more size series offered by some companies, but are much less common for Precision Angular Contact Bearings. These series were designed in a very interesting way to change the ID/OD and Width but keep the ID or keep the OD. Please refer to the depiction of the size correlations below or contact our engineers to learn more about universal bearing ball sizes.

Effects of Bearing Ball Size

Let’s examine the effects of ball size. These effects result from centrifugal forces that come from the size and more so weight of the ball(s) itself. The heavier the ball, the more the centrifugal forces will try to push the balls radially outward.

This increased centrifugal force then increases the internal forces from the ball to the raceway. There are limits to the amount of force the raceway(s) can handle before decreasing bearing life. This increased outward radial force will require an increased bearing (axial) preload to counteract this force.

Think back to elementary school when a teacher asked you to swing a bucket full of water around and around. The water did not fall out because of centrifugal forces. Now imagine the force on your arm if the bucket was empty vs. full…a big difference. This same effect happens with bearing ball weight/size.

To support the understanding of the interaction and effects of balls size, there are a couple of comparison tables below to show the differences between load and speed ratings.

Choosing the Right Bearing Size

When thinking about your specific application, the loads and RPM of the application will help to determine the proper design series and size series for your particular application. 

If your load and speed duty cycles are a bit complicated, or you just need some support, GMN Bearing USA engineers are happy to help.

Talk to an engineer