Bearings

Bearings, Mechanical Engineering, are those parts of the framework of a machine that support the rotating pieces, or are supported by them. That part of the rotating piece which fits in the bearing is called the journal, generally of cylindrical section. That portion of the bearing immediately In contact with the journal is called the bush, and is made of material somewhat softer than the journal, such as brass, gun-metal, or, in special cases, lignum-vitae. For the journal to rotate easily in the bearing it must be everywhere circular in section, it must fit the bearing accurately, and must admit of convenient lubrication (q.v.), the nature of which will depend on the speed of rotation and on the pressure at the bearing.

Ball-bearings have a special interest on account of their extensive application to cycles. In this case the journal does not fit accurately into the hollow cylindrical bush as usual, but is supported by a number of small steel balls fitting into a groove cut to contain them. The rolling-friction here, which replaces the ordinary rubbing-friction, is very small, and easy working at the bearing is ensured.