Ball bearing

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads.

Common ball bearing designs include angular contact, axial, deep-groove, and preloaded pairs.

Ball bearings are used in a wide range of applications, some of which include skateboards and centrifugal pumps.

[7] The industry standard life calculation is based upon the work of Lundberg and Palmgren performed in 1947.

Many variations of the formula exist that include factors for material properties, lubrication, and loading.

[7] If a bearing is not rotating, maximum load is determined by force that causes plastic deformation of elements or raceways.

The indentations caused by the elements can concentrate stresses and generate cracks at the components.

A second lesser form called false brinelling occurs if the bearing only rotates across a short arc and pushes lubricant out away from the rolling elements.

[7] If a sideways torque is applied to a deep groove radial bearing, an uneven force in the shape of an ellipse is applied on the outer ring by the rolling elements, concentrating in two regions on opposite sides of the outer ring.

If the outer ring is not strong enough, or if it is not sufficiently braced by the supporting structure, the outer ring will deform into an oval shape from the sideways torque stress, until the gap is large enough for the rolling elements to escape.

A sideways torque on a radial bearing also applies pressure to the cage that holds the rolling elements at equal distances, due to the rolling elements trying to all slide together at the location of highest sideways torque.

If the cage collapses or breaks apart, the rolling elements group together, the inner ring loses support, and may pop out of the center.

If the viscosity of the lubricant is lower than recommended, the lifespan of the bearing decreases, and by how much depends on which type of oil being used.

Greases with a high bleeding rate and low base oil viscosity should be preferred if possible.

Thrust bearings (commonly found on lazy susans) are specifically designed for axial loads.

[7] Often Conrad-style ball bearings will exhibit contact ellipse truncation under axial load.

When this is the case, it can significantly increase the stresses in the bearing, often invalidating rules of thumb regarding relationships between radial and axial load capacity.

[7] However, in order to correctly predict the rating life of ball bearings the ISO/TS 16281 should be used with the help of a calculation software.