Maximum bearing speed is determined by size and design. Generally, the smaller the bearing, the higher its speed capability. There are many influencing factors to limiting speeds such as:
- Cage design and material
- Lubrication type and delivery system
- Mounting procedure and fit
- Seal type
Bearings with contact type seals have a much lower maximum speed when compared to open or non-contact sealed types.
Oil lubricated bearings will have a higher maximum speed than a grease lubricated bearing due to lubricant shear and will run cooler.
A rigid preloaded pair of bearings will have a reduced maximum speed when compared to a spring preloaded pair.
Along with RPM ratings bearing speed limitations can be expressed using the following formula:
dN=Bearing bore in millimeters multiplied by RPM
dN values can be assigned to bearing types and their components such as retainers and lubricants.
For example precision angular contact bearings should be limited to around 850,000 dN. Deep groove radial ball bearings with standard metal retainers should not exceed around 250,000 dN.
Of course with modifications to materials and design these values can be exceeded such as improved retainer design, ceramic hybrids, and improved lubrication processes.