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:
“Why does not the kitten betray some of the attributes common to the adult puss? A puppy is but a dog, plus high spirits, and minus common sense. We never hear our friends say they love puppies, but cannot bear dogs. A kitten is a thing apart; and many people who lack the discriminating enthusiasm for cats, who regard these beautiful beasts with aversion and mistrust, are won over easily, and cajoled out of their prejudices, by the deceitful wiles of kittenhood.”
—Agnes Repplier (1858–1950)
“I set forth a humble and inglorious life; that does not matter. You can tie up all moral philosophy with a common and private life just as well as with a life of richer stuff. Each man bears the entire form of man’s estate.”
—Michel de Montaigne (1533–1592)
“In the whole vast dome of living nature there reigns an open violence, a kind of prescriptive fury which arms all the creatures to their common doom: as soon as you leave the inanimate kingdom you find the decree of violent death inscribed on the very frontiers of life.”
—Joseph De Maistre (1753–1821)