Almost every technician has encountered abnormal noise generated by bearing assemblies. Nevertheless, abnormal bearing noise does not necessarily stem from product quality defects. Based on long-term technical summaries, thirty common causes of bearing noise are listed below. Additional unencountered causes may exist, and supplements are welcome.
Summary of Thirty Causes of Abnormal Bearing Noise
Impurities contained in grease;
Insufficient lubrication (low oil level, or leakage of oil/grease via seals due to improper storage);
Excessively small or large bearing internal clearance (manufacturing defect);
Foreign particles such as sand grains or carbon particles enter the bearing and act as abrasives;
Contaminants including water, acids or paint enter the bearing and trigger corrosion;
The bearing is squeezed and deformed in the housing bore (poor roundness or distortion of the housing bore);
Uneven shims under the bearing base (resulting in housing bore deformation or even cracks on the bearing housing);
Residual debris inside the bearing housing bore (such as metal chips and dust particles);
Eccentric sealing ring (contact and friction with adjacent components);
Extra load applied to the bearing (axial binding, or two fixed-end bearings mounted on one shaft);
Loose fit between bearing and shaft (undersized shaft diameter or untightened adapter sleeve);
Insufficient bearing clearance leading to overtight rotation (over-tightened adapter sleeve);
Bearing noise caused by slipping of roller end faces or steel balls;
Excessive thermal elongation of the shaft (inducing static indeterminate additional axial load on the bearing);
Overlarge shaft shoulder (contact and friction with bearing seals);
Overlarge shoulder of the housing bore (distorting the bearing seals);
Undersized clearance of labyrinth seal (friction against the shaft);
Bent teeth of lock washer (contact and friction with the bearing);
Improper position of oil slinger (contact and friction with flange cover);
Indentations on steel balls or rollers (caused by hammering during installation);
Bearing noise induced by external vibration sources;
Thermal discoloration and deformation of the bearing (caused by heating with spray guns during disassembly);
Oversized shaft resulting in excessive interference fit (causing high bearing temperature or noise);
Undersized housing bore diameter (leading to excessive bearing temperature);
Oversized housing bore diameter resulting in excessively loose fit (high bearing temperature – outer ring creeping);
Enlarged bearing housing bore (non-ferrous metal housing stretched or expanded due to thermal expansion);
Broken bearing cage;
Rust on bearing raceways;
Wear of steel balls and raceways (unqualified grinding processing or collision damage);
Unqualified raceways of bearing rings (manufacturing defect).