The terms axial ball bearing or thrust ball bearing can be used interchangeably. Sometimes, they are even combined together, referred to as ‘axial thrust bearings’. This group of bearings has been designed to endure an axial load, also known as a thrust load, which is a force in the same direction as the shaft. The axial bearings should not be subjected to any radial load as they are designed for thrust loads only.
Think office chairs, lazy Susan turntables or bar stools, to name just a few axial load applications. While this group of bearings are unable to handle radial loads — they can be used in conjunction with radial ball bearings if required. A radial ball bearing’s rolling elements are designed to support radial loads, which is a load that is perpendicular to the shaft.
Axial load direction
However you refer to these bearings in the axial bearing vs thrust bearing debate, it is important to use the correct type of miniature thrust bearing based on the direction of the thrust load. Some have a raceway or groove on each washer. In these instances, one washer has a slightly larger inside diameter so that it is located in the housing and the shaft can rotate inside it. These bearings can accommodate thrust loads in one direction only and must be installed according to the load direction.
The more straight-forward type of miniature thrust bearing has identical washers and no raceway. These can accept endure axial loads in either direction but have reduced load and speed ratings compared with single-direction axial bearings.
Axial load ratings
Different applications put different load requirements on the bearings. For high axial load applications, heavy duty bearing types such as 6200 or 6300 series may take axial loads of up to 50 per cent of the static radial load rating. In cases where large axial and radial loads occur simultaneously, angular contact bearings may be required.
For low axial load applications, some radial bearings can be used. Thin-section deep groove ball bearings can support axial loads of between 10 and 30 per cent of the bearing's static radial load rating. Note — these figures are based on pure axial load. Additional radial loads or moment (misalignment loads) will have an impact on the axial load capacity.
Regardless of the loading type required, all bearings have their limits. When determining which bearing to choose, it is important to consider several factors; load direction, load size, turning speed of the application. It is also crucial to ensure the bearings are manufactured to high quality standards, which enables the highest levels of rollability even with heavier axial forces.
Getting it right
Exceeding the total recommended limits for combined loads will have a detrimental effect on bearing life.
When choosing a thrust bearing, it’s important to seek the right advice, as these bearings can be very unforgiving when axial forces are in play.
If you would like more help on different types of loading, contact bearing supplier SMB Bearings. We have years of experience supplying small and miniature bearings to a range of industries. Call our experts today on +44 (0) 1993 842 555 or e-mail sales@smbbearings.com.