Scratching phenomenon on the outer diameter of the bearing rolling elements: circumferential dents in the contact area of u200bu200bthe rolling elements. There are generally parallel circumferential traces on the rollers, see Figures 70 and 71, and balls often show a yarn ball phenomenon, 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 are often embedded in the cage pockets, causing galling, see Figure 73. Cause: Contaminated lubricant; hard particles embedded in cage pockets act like abrasive particles on grinding wheels Remedies: Ensure clean installation conditions Improve sealing Filter lubricants. 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 the form of dots, see Figures 74 and 75. Minor pitting is often found, see section 3.3.2.1 Fatigue due to poor lubrication. Cause: When the load is too low and the lubrication is poor, the rolling elements slip on the raceways. Sometimes also because the load-bearing area is too small, the rollers decelerate rapidly in the cage pockets in the non-load-bearing area, and then accelerate sharply when entering the load-bearing area. Speed u200bu200bchanges rapidly. Remedy: Use a bearing with low load capacity. Bearing preload, such as reducing bearing clearance with spring , the rolling elements and raceways are missing material 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, install components with a slow turn.