A bearing is a set of mechanical elements which has a task to support rotating elements of machines (e.g. shafts, axles), assuring lowest possible friction and transmitting their loads to base. In order to fulfil these tasks which are rotation movement of the shaft, maintaining the axis of revolution in the fixed position and transmission of loads bearings should be characterized by low movement resistances, stable work, operational reliability and resistance to wear, which is high durability. They should meet certain technical and construction requirements.

The history of bearings dates from 330 b.c. when Greek engineer Diaden invented supposedly one of first rolling bearings for trestles on warships. In later years between 1452 to 1519 further developement of rolling bearings took place by dint of Leonardo da Vinci. In 1794 regular ball bearing was patented by Ph. Vaughan in England. Eventually in 1802 M. Cardinet patented tapered roller bearing.

A rolling bearing is a bearing in which movement is provided by rolling elements (balls, taper roller, needle rollers etc.) placed between bearing rings. An inner ring (1) is placed tightly on the shaft or on an other element. An outer ring(2) is placed in a housing or in an other bearer element. Rolling elements (3) are placed between rings and touch raceways of outer and inner rings providing rotation movement of rings against each other. Additional elements of bearings may be retainers that keep rolling elements in fixed distance between each other, shields, oil seals etc..

Basic dimensions of bearings are: D - outer diameter of a bearing d - inner diameter of a bearing B - width of a bearing (H - height of a thrust bearing) R, r - radiuses of outer and inner rings

The highest demand for bearings comes from industry. Not so long ago main customers for bearings were coal mines which significantly restricted their activities now. A high demand for bearings is also present in automotive. We see an increased number of cars on the streets and bearings are requisitive parts of cars and bikes. A commonly known rule of bearing rotation movement is still valid today and nothing portents that it will change.
The biggest tycoons in bearing field are giants like TIMKEN, FAG, NSK and SKF.