Raceways and rolling elements may become dented if the mounting pressure is applied to the wrong ring, so that it passes through the rolling elements, or if the bearing is subjected to abnormal loading while not running. Foreign particles in the bearing also cause indentations.
Indentations caused by faulty mounting or overloading
The distance between the
dents is the same as the rolling element spacing. Ball bearings are prone to indentations
if the pressure is applied in such a way that it passes through the balls during the
mounting or dismounting operations. Self-aligning ball bearings are particularly
susceptible to damage in such circumstances. In spherical roller bearings the damage
originates as smearing and subsequently, if the pressure
increases, develops into a dent. The same conditions apply in taper roller bearings that
are unduly preloaded without being rotated.
Figures 2-4 are examples of the results of improper handling. A roller in a double row cylindrical roller bearing has suffered impact (fig 2). A periphery camera view of the roller shows two diametrically opposed indentations (fig 3). The roller has, in turn, dented the inner ring raceway (fig 4).
Indentations caused by foreign particles
Foreign particles, such as swarf and burrs, which have gained entry into the bearing cause indentations when rolled into the raceways by the rolling elements. The particles producing the indentations need not even be hard. Thin pieces of paper and thread from cotton waste and cloth used for drying may be mentioned as instances of this. Indentations caused by these particles are in most cases small and distributed all over the raceways.
Figure 5 -
Indentations, caused by dirt, in one of the raceways of a roller bearing - 50 x