Most small bearings are used in applications where rotational accuracy and low torque are primary requirement and loads are light. Therefore the operating lifetime of the bearing is relatively long, and, if properly operated, failure is rare. Nevertheless, all bearings have a finite life under use and will eventually fail to perform satisfactorily due to an increase in noise and vibration, loss of running accuracy, deterioration of lubricant, or fatigue flaking of the rolling surfaces. Such failure modes are considered "normal" and can be predicted using standardized techniques.
In addition to normal deterioration, bearings may fail due to heat seizure, fracture, scoring of the rings and other conditions caused by improper use, selection or maintenance of the bearing. Such failures are not normal and can only be avoided by careful handling and correct operation of the bearing in a given application.