Scratch phenomenon on the outer diameter of the bearing rolling elements: circumferential dents in the contact area of ​​the rolling elements. There are generally parallel circumferential traces on the rollers, see Figures 70 and 71, and a “hairball” phenomenon is often present for balls, see Figure 72. Not to be confused with edge traces (see section 3.3.2.6). The edge of the track formed by the edge running is smooth due to plastic deformation, while the scratch has sharp edges. Hard particles often become embedded in the cage pockets, causing galling, see Figure 73. Cause: Contaminated lubricant; hard particles embedded in the cage pockets act like abrasive particles on the grinding wheel Remedy: – guarantees clean installation conditions – improves sealing – filters out the lubricant.

Slip marks phenomenon: rolling elements slip, especially large and heavy rollers, such as INA full complement roller bearings. Slip roughens raceways or rolling elements. Material often builds up with drag marks. Usually not evenly distributed on the surface but in spots, see Figures 74 and 75. Minor pitting is often found, see section 3.3.2.1 “Fatigue due to poor lubrication”. Causes: – When the load is too low and the lubrication is poor, the rolling elements slip on the raceways. Sometimes because the bearing area is too small, the rollers decelerate rapidly in the cage pockets in the non-loading area, and then accelerate sharply when entering the bearing area. – Rapid changes in speed. Remedial measures: – Use bearings with low load capacity – Preload the bearings, e.g. with springs – Reduce bearing play – Ensure sufficient load even when empty – Improve lubrication

Bearing scratching phenomenon: For separable cylindrical roller bearings or tapered roller bearings, the rolling elements and raceways are missing material that is parallel to the axis and equidistant from the rolling elements. Sometimes there are several sets of marks in the circumferential direction. This trace is usually found only in the circumferential direction of about B/d rather than the entire circumference, see Figure 76. Cause: Misalignment and rubbing against each other when installing a single ferrule and a ferrule with rolling elements. It is especially dangerous when moving components of large mass (when the thick shaft with the bearing inner ring and rolling element assembly is pushed into the outer ring already installed in the bearing housing). Remedy: – Use suitable installation tools – Avoid misalignment – ​​If possible, turn slowly when installing components.