Ball Bearings

Ball bearings help reduce friction and improve efficiency by minimizing the frictional contact between machine parts through bearings and lubrication. Ball bearings allow rotary or linear movement between two surfaces. As the name indicates, a ball bearing involves a number of balls, typically steel, sandwiched between a spinning inner race (a small steel ring with a rounded grove on its outer surface) and a stationary outer race (a larger steel ring with a rounded grove on its inner surface). These balls are held in place by a cage or a retainer. The sides often have shield or seal rings to retain the grease or some other lubrication and to keep the bearing as clean as possible. The area of contact between the balls and the moving parts is small, therefore friction and heat is low. Bearings based on rolling action are called rolling-element bearings and contain cylindrical rollers instead of balls, but operate on the same principle.

A bearing can carry loads along its axis of rotation or perpendicular to its axis of rotation. Those carrying loads along the axis of rotation are referred to as thrust bearings. Rolling-element bearings carrying loads perpendicular to the rotational axis are called radially loaded bearings.

Ball bearings are generally used for small to medium size loads and are suitable for high speed operation. The type of bearing used is dependent on the application. An engineer will evaluate a bearing based on load, speed that they can carry this load, and required life expectancy under specified conditions. Friction, start-up torque, ability to withstand impact or harsh environments, rigidity, size, cost, and complexity also are important design considerations.