Editing Rolling-element bearing (section)

{{short description|Bearing which carries a load with rolling elements placed between two grooved rings}}
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[[File:Radial-deep-groove-ball-bearing din625-t1 2rs 120.png|thumb|A sealed deep groove ball bearing]]

In [[mechanical engineering]], a '''rolling-element bearing''', also known as a '''rolling bearing''',<ref name=":0">ISO 15</ref> is a [[bearing (mechanical)|bearing]] which carries a load by placing rolling elements (such as balls, cylinders, or cones) between two concentric, [[Groove (engineering)|grooved]] rings called [[Race (bearing)|races]]. The relative motion of the races causes the rolling elements to [[rolling|roll]] with very little [[rolling resistance]] and with little [[sliding (motion)|sliding]].

One of the earliest and best-known rolling-element bearings is a set of logs laid on the ground with a large stone block on top. As the stone is pulled, the logs roll along the ground with little [[sliding friction]]. As each log comes out the back, it is moved to the front where the block then rolls onto it. It is possible to imitate such a bearing by placing several pens or pencils on a table and placing an item on top of them. See "[[bearing (mechanical)|bearing]]s" for more on the historical development of bearings.

A rolling element rotary bearing uses a shaft in a much larger hole, and spheres or cylinders called "rollers" tightly fill the space between the shaft and the hole. As the shaft turns, each roller acts as the logs in the above example. However, since the bearing is round, the rollers never fall out from under the load.

Rolling-element bearings have the advantage of a good trade-off between cost, size, weight, carrying capacity, durability, accuracy, friction, and so on. Other bearing designs are often better on one specific attribute, but worse in most other attributes, although [[fluid bearing]]s can sometimes simultaneously outperform on carrying capacity, durability, accuracy, friction, rotation rate and sometimes cost. Only [[plain bearing]]s are used as widely as rolling-element bearings. They are commonly used in automotive, industrial, marine, and aerospace applications. They are products of great necessity for modern technology. The rolling element bearing was developed from a firm foundation that was built over thousands of years. The concept emerged in its primitive form in [[Ancient Rome|Roman times]].<ref name=":1">{{Cite journal |last=Hamrock, B. J.; Anderson, W. J.|date= June 1, 1983|title=Rolling-Element Bearings|url=https://ntrs.nasa.gov/search.jsp?R=19830018943|website=NASA Technical Reports Server}}</ref> After a long inactive period in the Middle Ages, it was revived during the [[Renaissance]] by [[Leonardo da Vinci]], and developed steadily in the seventeenth and eighteenth centuries.