Scratch phenomenon on the outer diameter of the rolling elements of a failed bearing: circumferential dents in the contact area of u200bu200bthe rolling elements. There are parallel circumferential traces on the rollers, see Figures 70 and 71, and balls often show a ball of yarn, 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 in failed bearings: Rolling element slippage, especially in large and heavy-duty roller bearing models, such as full complement 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 bearings with low load capacity Bearing preload, eg with springs Reduce bearing clearance Ensure sufficient load also when empty Improve lubrication.