Bearing clearance is the total distance one bearing ring can be moved relative to the other. As shown in the accompanying diagram, there are two types of bearing clearance:
- Radial clearance (up-and-down movement)
- Axial clearance (side-to-side movement)
Most rolling element style mounted bearings have some degree of internal clearance to:
- allow for free rotation of the inner ring;
- prevent metal-to-metal contact between rolling elements and raceways; and
- accommodate for thermal growth of internal components.
If the bearing clearance is not selected properly, it will affect bearing function and lifespan. ISO standards have established five clearance classes for many bearing types. These classes are referred to as:
- C2 = smaller than normal
- C0 = normal clearance
- C3 = greater than normal
- C4 = greater than C3
- C5 = greater than C4
The classification you select depends on several factors, including operating temperature, operating speed, applied bearing loads and other conditions. Working with the Rexnord Bearing Application Engineering group, you can ensure the proper clearance range to maximize performance and bearing life for your application.
Our Rex and Link-Belt mounted spherical roller bearings allow for easy, field-adjustable clearance simply by tightening or loosening a threaded cover. This eliminates the need for a specialized clearance bearing. And it’s just one of the key advantages our products offer to help reduce lead time for custom bearings.
Metal-to-metal contact within a bearing is never good and will lead to increases in operating temperature, noise and surface fatigue, which in turn lead to bearing failure. In the steel industry, on applications such as large furnaces, where bearings endure operating temperatures up to 400°F (204°C), having bearings with increased internal clearance is critical to allow for components to expand without contacting each other.
Within our bearing product line, we can provide all classes of bearing clearance to fit your application needs. If you have questions or would like to talk to one of our application engineers, call (317)273-5781 or email bearing.tech.support@rexnord.com. For videos and other demos, visit our YouTube channel.