Bearings reduce friction between two moving surfaces, and from that job they wear down and eventually break. To best keep bearings rolling for as long as they can, some maintenance is required in various parts of the lifespan.
Bearings are shipped and stored with a thin layer of manufacturing oil to preserve the bearing. If this coating is wiped off, smudged through handling, or dries out the bearing can rust or the lubrication can become useless. While storing bearings make sure to keep the bearing coated with preservative oils.
Bearings are designed to have an interference shaft fit on the shaft during application. This fit is built into the dimensions and is accounted for. If a bearing is installed onto a shaft too big or too small, the difference in clearance can wear the bearing much quicker than specified.
Proper lubrication is necessary to reduce heat, and friction within the bearing itself. Due to the properties of lubricating oils, bearings may leak and can be sealed by silicone rings or sealing grease.
Through continuous use of bearings, lubricating greases and oils with wear out just as much as the interior rollers in the bearing. Properly replacing and refilling the lubricant of a bearing will extend the life of the bearing. Some manufacturers provide charts for re-greasing intervals, check with the OEM of your bearing for details.
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