Characteristics of rolling bearings

Rolling bearings come in many shapes and varieties, each with its own distinctive features. However, when compared with sliding bearings, rolling bearings all have the followings advantages:

• The starting friction coefficient is lower and only a little difference between this and the dynamic friction coefficient is produced.
  
• They are internationally standardized, interchangeable and readily obtainable.
  
• Ease of lubrication and low lubricant consumption.
  
• As a general rule, one bearing can carry both radial and axial loads at the same time.
  
• May be used in either high or low temperature applications.
  
• Bearing rigidity can be improved by preloading. Construction, classes, and special features of rolling bearings are fully described in the boundary dimensions and bearing numbering system section.
  

Ball bearings and roller bearings

Generally speaking, when comparing ball and roller bearings of the same dimensions, ball bearings exhibit a lower frictional resistance and lower face run-out in rotation than roller bearings.

This makes them more suitable for use in applications which require high speed, high precision, low torque and low vibration. Conversely, roller bearings have a larger load carrying capacity which makes them more suitable for applications requiring long life and endurance for heavy loads and shock loads.

Almost all types of rolling bearings can carry both radial and axial loads at the same time. Generally, bearings with a contact angle of less than 45° have a much greater radial load capacity and are classed as radial bearings; whereas bearings which have a contact angle over 45° have a greater axial load capacity and are classed as thrust bearings. There are also bearings classed as complex bearings which combine the loading characteristics of both radial and thrust bearings.

Standard bearings and special bearings

Bearings which are internationally standardized for shape and size are much more economical to use, as they are interchangeable and available on a worldwide basis. However, depending on the type of machine they are to be used in, and the expected application and function, a nonstandard or specially designed bearing may be best to use. Bearings that are adapted to specific applications, and “unit bearings” which are integrated (built-in) into a machine’s components, and other specially designed bearings are also available.