Common
By far, the most common bearing is the plain bearing, a bearing which uses surfaces in rubbing contact, often with a lubricant such as oil or graphite. A plain bearing may or may not be a discrete device. It may be nothing more than the bearing surface of a hole with a shaft passing through it, or of a planar surface that bears another (in these cases, not a discrete device); or it may be a layer of bearing metal either fused to the substrate (semi-discrete) or in the form of a separable sleeve (discrete). With suitable lubrication, plain bearings often give entirely acceptable accuracy, life, and friction at minimal cost. Therefore, they are very widely used.
However, there are many applications where a more suitable bearing can improve efficiency, accuracy, service intervals, reliability, speed of operation, size, weight, and costs of purchasing and operating machinery.
Thus, there are many types of bearings, with varying shape, material, lubrication, principle of operation, and so on.
Read more about this topic: Bearing (mechanical)
Famous quotes containing the word common:
“Now that the election is over, may not all, having a common interest, re-unite in a common effort, to save our common country?”
—Abraham Lincoln (1809–1865)
“The common cormorant or shag
Lays eggs inside a paper bag.”
—Christopher Isherwood (1904–1986)
“Uniform ideas originating among entire peoples unknown to each other must have a common ground of truth.”
—Giambattista Vico (1688–1744)