Ball Bearings: Inner vs Outer Races Explained

Ball bearing by Monroe

When researching the parts of a typical ball bearing, you may come across the terms “inner races” and “outer races.” Ball bearings are used to reduce friction and position moving machinery parts. As their name suggests, they contain balls — typically steel or other metal balls. Ball bearings, however, contain inner and outer races as well.

The Basics of Ball Bearing Races

A ball bearing race is essentially a ring with a uniform groove on one side. This groove supports the balls. The balls will roll along the race, always staying in its groove.

What Is an Inner Race?

There are inner races, and there are outer races. They are both rings with a uniform groove on one side.

An inner race is a type of ball bearing race that serves as the inner perimeter for the balls. Ball bearings are typically placed around shafts. By serving as the inner perimeter for the balls, the inner race will be closest to the shaft.

What Is an Outer Race?

An outer race is a type of ball bearing race that serves as the outer perimeter for the balls. The balls in a ball bearing are designed to glide during use. Both the inner and outer races work together to allow them to glide while simultaneously containing them.

All ball bearings have an inner race and an outer race. The former consists of an inner ring-based perimeter, whereas the latter consists of an outer ring-based perimeter. The balls of a bearing bearing will be sandwiched between the inner and outer ring.

How Inner Races and Outer Races Differ

Inner and outer races typically feature the same uniform groove. This ensures the balls can glide and roll smoothly during use. With that said, outer races are always longer than inner races.

Outer races are found on the outside of the balls, so they are longer than their inner counterparts. They are still made of the same material, and they usually feature the same uniform groove. Nonetheless, outer races are longer than inner races.

What About Cages?

In addition to an inner and outer race, many ball bearings feature a cage. Also known as a ball bearing separator, a cage is a component that’s designed to separate the balls. It features holes or spaces at specific intervals, each of which is designed to hold a ball. With a cage, the balls will be evenly spaced as they glide and roll.

Looking for Bearings?

Click below to browse Monroe's Bearings!

Browse Bearings