- 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
For additional information, refer to Operating temperature and speed.
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.