How full should a ball bearing be filled with grease for optimal performance?

For optimal performance, a ball bearing should typically be filled with grease to about one-third full. This amount allows for sufficient lubrication without overfilling, which can lead to excessive pressure and lead to grease leakage or the formation of air pockets within the bearing. When the bearing is one-third full, there is enough grease to ensure a good lubricating film and to reduce wear and friction between the moving parts while also allowing for proper heat dissipation.

Overfilling to half or completely full can lead to the grease being squeezed out of the bearing, thereby reducing effectiveness and potentially causing issues with the bearing's operation. Conversely, a quarter full would not provide enough lubrication, leading to increased wear and possibly premature failure. Therefore, filling to about one-third strikes the right balance for optimal lubrication and performance.