By Joyce Laird,  Contributing Editor

What is different about self-aligning bearings vs. basic bearings?

In a self-aligning bearing, the inner ring has two raceways and the outer ring has a single spherical raceway with its center of curvature coincident with the bearing axis. This allows the axis of the inner ring, balls and cage to deflect around the bearing center to automatically correct misalignment caused by housing and shaft machining or installation error.

Paul Brda, Application Engineer, NSK Americas explains, "Whereas a ball bearing only has one raceway groove on both the inner and outer ring and is the most common type of rolling bearing."

Why would you choose to use self-aligning bearings?

Self aligning bearing cut-away image

A self-aligning bearing is recommended when the alignment of the shaft and housing is difficult or when the shaft may bend during operation. Brda notes that similar to deep groove ball bearings, most self-aligning ball are for general use.

Can they interchange with standard ball bearing assemblies?
Depending on the series, most self-aligning bearings can be interchanged with standard ball bearing assemblies. (6200 and 6300 have direct interchanges with the 1200 and 1300 series). "However, if this is not possible, the self-aligning bearing may be wider or can have a tapered bore," Brda explains.

Selection and Installation tips

According to Brda, the bearing would be selected based on the load, speed and space constraints of the application. Also, the misalignment and/or shaft bending amount should be considered when specifying bearing type.

Normal mounting and handling procedures for a cylindrical bore bearing should be followed. For the tapered bore, special care must be taken to ensure the bearing is driven up the taper the appropriate amount. Because matching the bearing to the specific application is critical, it is important to verify your application need with your selected vendor.