Scratch phenomenon on the outer diameter of the rolling element of the bearing: the circumferential dent in the contact area of u200bu200bthe rolling element. There are generally parallel circumferential traces on the rollers, see Figures 70 and 71. For balls, the phenomenon of yarn balls often appears, see Figure 72. Not to be confused with edge marks (see section 3.3.2.6). The edge of the trajectory formed by the edge movement is smooth due to plastic deformation, and the abrasion has a sharp edge. Hard particles are often embedded in the cage pockets, causing scratches, see Figure 73. Reason: contaminated lubricant; hard particles embedded in the cage pockets, which act like abrasive particles on the grinding wheel. Remedial measures: to ensure clean installation conditions, improve sealing, and filter lubricant. Slip marks phenomenon: the rolling elements slip, especially large and heavy rollers, such as full complement roller bearings. Slip causes the raceway or rolling elements to become rough. The material is often piled up and accompanied by drag marks. It is usually not evenly distributed on the surface but in dots, see Figures 74 and 75. Small pitting corrosion is often found, please refer to section 3.3.2.1 of fatigue caused by poor lubrication. Reason: When the load is too low and the lubrication is poor, the rolling elements slip on the raceway. Sometimes because the load-bearing area is too small, the roller decelerates rapidly in the cage pockets of the non-load-bearing area, and then accelerates sharply when entering the load-bearing area. The speed changes rapidly. Remedial measures: Use bearings with low load-bearing capacity to preload the bearings. For example, use springs to reduce the bearing clearance and ensure sufficient load to improve lubricating bearing scratches: For separable cylindrical roller bearings or tapered roller bearings , The rolling elements and raceways have missing materials that are parallel to the axis and equally spaced from the rolling elements. Sometimes there are several sets of marks in the circumferential direction. Usually there is this trace only in the circumferential direction of about B/d instead of the entire circumferential direction, see Figure 76. Reason: When installing a single ferrule and a ferrule with rolling elements, they are misaligned and rubbed against each other. It is especially dangerous when moving components with large masses (when the thick shaft equipped 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 to avoid misalignment. If possible, rotate slowly when installing the components.