Basics of bearing speeds

There is a limit to the speed at which rolling bearings can be operated. Generally, the temperature limit of the lubricant or the material of the bearing components sets the speed limit.
The speed at which a bearing reaches its operating temperature limit depends on the heat generated in the bearing, any externally applied heat, and the amount of heat that can be transferred away from the bearing.
The amount of heat generated in the bearing depends on the bearing type and size, internal design, load, lubrication and alignment. Other factors include cage design, accuracy and internal clearance.
In the product tables, two speeds are generally listed: reference speed (thermal) and limiting speed (mechanical).
In general, the limiting speed is higher than the reference speed for a bearing. For some bearing series, however, due to favourable frictional characteristics compared to the mechanical ability of the bearing to sustain high speeds, the reference speed can be higher than the limiting speed. In every case, however, the limiting speed of the bearing must always be observed, even under the most favourable operating conditions.
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