The object of ball bearings (and roller bearings) is the substitution of pure rolling motion for plain sliding friction.
Ball Bearings rely on the rolling motion of hardened steel balls to absorb loads. This rolling motion produces far less friction than the sliding motion. These steel balls are held in circular rows between an outer and inner ring, which have raceways, or slots, grooved into them to guide the balls. Ball bearings are available in both filling-slot and no filling-slot types. Other types of bearings have developed from these basic designs, like double-row and deep groove bearings, to handle specific application. No filling-slot bearings have a deep uninterrupted raceway, which allows them to carry both high radial loads as well as moderate Thrust loads. Filling-slot bearings have more balls than no filling bearings of comparable size. This gives them a higher radial load capacity, but Thrust loads must be light.
Types of Ball bearing systems:
Rigid single row ball bearing. – Basic type of bearing widely used. The balls run in comparatively deep grooved tracks, which make the bearing suitable for both radial (journal) load and axial thrust load. The bearing provides location of the shaft in relation to the housing when provided with suitable means of clamping.
Rigid single row bearing with filling slots for balls. – This bearing contains more balls than the standard type and can therefore take heavier radial loads but only limited thrust.
Rigid double row bearing. – For heavy radial loads and to provide greater rigidity. Requires accurate location if used in conjunction with another bearing.
Self-aligning double row bearing. – For applications in which slight deflections cannot be avoided when rotating.
Aligning single row bearing. – This bearing will correct initial angular misalignment between shaft and housing but is not designed to accommodate shaft deflection or misalignment when rotating.
Angular contact single row bearing. – Gives precise axial location under thrust load. May be used in pairs to accommodate thrust in either direction.
Duplex bearing. – Used to take heavy thrust in either direction or some radial load.
Adaptation sleeve bearing. – This bearing is mounted on a tapered split sleeve to simplify assembly on long shafts.
No matter what type of ball bearing system they all have one common function, to turn sliding forces into rotational forces, so that the coefficient of friction is reduced and hence so is the force opposing the motion (friction). There is some friction but this is much lower than if two surfaces where slid over the top of each other.