- the reference speed, which enables a quick assessment of the speed capabilities from a thermal frame of reference
the limiting speed, which is a mechanical limit that should not be exceeded unless the bearing design and the application are adapted for higher speeds
When operating at ndm values approaching or exceeding 20 000 mm/min, the relubrication interval for grease can become very short (→ Selecting grease or oil). Therefore, oil lubrication is commonly used.
For additional information, refer to Operating temperature and speed.