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:
“The desire to serve the common good must without fail be a requisite of the soul, a necessity for personal happiness; if it issues not from there, but from theoretical or other considerations, it is not at all the same thing.”
—Anton Pavlovich Chekhov (1860–1904)
“But neither milk-white rose nor red
May bloom in prison air;
The shard, the pebble, and the flint,
Are what they give us there:
For flowers have been known to heal
A common man’s despair.”
—Oscar Wilde (1854–1900)
“If music in general is an imitation of history, opera in particular is an imitation of human willfulness; it is rooted in the fact that we not only have feelings but insist upon having them at whatever cost to ourselves.... The quality common to all the great operatic roles, e.g., Don Giovanni, Norma, Lucia, Tristan, Isolde, Brünnhilde, is that each of them is a passionate and willful state of being. In real life they would all be bores, even Don Giovanni.”
—W.H. (Wystan Hugh)