A bearing is a structural element enabling the transfer of forces between other elements whose working surfaces move at different rotational speeds. Moreover, bearings ensure the proper operation of rotating machine elements (axes, shafts and machine parts mounted on them) by maintaining a constant position of the rotation axis of these elements in relation to a stationary base, e.g. a gear housing. The mounting bearing is used to determine the position of axles and shafts with machine bodies.
The purpose of the bearing is to transfer the force resulting from the load on shafts and axles, as well as the load resulting from their weight and the weight of the elements mounted on them, e.g. pulleys and gears, clutches, etc.
We distinguish between sliding and rolling bearings.
The principle of operation of plain bearings is based on sliding friction. Most often, the surface of the shaft journal slides on the surface of the bearing shell (this is the part of the bearing cooperating with the journal), less often directly on the surface of the bearing bore.
Rolling bearings contain rolling elements such as balls or rollers that facilitate the rolling of the mating surfaces of the bearing rings. This results in the conversion of sliding friction into more favorable rolling friction.
Rolling bearings supporting shafts and axles have dimensions ranging from millimeters to several or even several meters (e.g. in earthmoving machines).
The advantages and disadvantages of both types of bearings determine their use.