The rotational speed of a bearing is normally affected by friction heat generated in the bearing. If the heat exceeds a certain amount, seizure or other failures occur, thus causing rotation to be discontinued.
The limiting speed is the highest speed at which a bearing can continuously operate without generating such critical heat.
The limiting speed differs depending on various factors including bearing type, dimensions and their accuracy, lubrication, lubricant type and amount, shapes of cages and materials and load conditions, etc.
The limiting speed determined under grease lubrication and oil lubrication (oil bath) for each bearing type are listed in the bearing specification table. These speeds are applied when bearings of standard design are rotated under normal load conditions.
Limiting speed for sealed ball bearings
The limiting speed of ball bearings with a contact seal are determined by the rubbing speed at which the seal contacts the inner ring. These allowable rubbing speeds differ depending on seal rubber materials.
Bearing for high speed
When bearings are used for high speed, especially when the rotation speed approaches the limiting speed or exceeds it, the following should be considered:
- Use of high precision bearings
- Study of proper internal clearance
(Reduction in internal clearance caused by temperature increase should be considered.) - Selection of proper cage type and materials
(For high speed, copper alloy or phenolic resin machined cages are suitable. Synthetic resin molded cages for high speed are also available.) - Selection of proper lubrication
(Suitable lubrication for high speed should be selected jet lubrication, oil mist lubrication and oil air lubrication, etc.)