Most machines and vehicles depend on bearings for precision operation. Bearings do this by permitting low-friction rotary or linear movement between two surfaces, either through sliding or rolling action. These allow faster transportation of materials and goods in the operating line or smooth movement for transportations.

To keep friction at a minimum level, a sufficient amount of lubrication should be applied. This keeps the bearing surfaces separated by a film of oil. Less friction means longer service lives for the bearings. Aside from friction, other factors are considered in the design of the bearings. These include start-up torques or forces, ability to withstand impact or harsh environments, rigidity, size, cost and complexity. When choosing the right kind of bearings, consider how much load they can carry, how fast they can carry the load and how long before they give out under the specified conditions and elements.

There are the different types of bearings: precision ground radial bearings, semi-ground radial bearings, semi-ground radial bearings, extended inner with flanged housing, heavy duty precision ground radial bearings, heavy duty precision ground radial bearings with extended inner ring, single row ungrounded radial bearings, single row ungrounded flanged radial bearings, single row ungrounded combination radial and thrust bearings and ungrounded thrust bearings.

Bearings, suffering from too much friction, usually give out noises. When you hear such noises, be sure to lubricate the bearings before proceeding. Most bearings only require this kind of maintenance to live long. Bearings could last years before giving way to wear and tear.

The Society of Tribologists and Lubrication Engineers (STLE) have come out with improvements and innovations that improved the life of bearings. The book, "STLE Life Factors for Rolling Bearings will give you the expected life of both ball bearings and roller bearings.