After the bearing is cleaned and inspected, it will be measured and repaired. This part includes 5 processes. This is the bearing part that is ready to enter the assembly process after inspection and screening, and is the basic process to ensure the quality of bearing assembly.

1. Measurement of the quality of the fit between the bearing inner ring and the shaft. The importance of the quality of the interference fit of the mating pair has been described in detail before, but there was no method to effectively measure the quality of the assembled assembly in the installed state. In the early 1980s, the instrument for measuring the contact resistance of electrical contacts developed by the Shanghai Railway Institute passed the ministerial appraisal, thus providing a material basis for the inspection of the quality of the bearing inner ring and the shaft. The specific method is to judge the matching quality of the two by measuring the contact resistance value of the bearing inner ring and the shaft. The distance between the measuring points in the figure must be strictly specified to be comparable, and the resistance values u200bu200bof the three parts are different when the measuring points are different. The measured resistance is actually the sum of the resistance of the bearing inner ring and the armature shaft, plus the resistance of the two contact surfaces. Since the latter value is one or even several orders of magnitude larger than the first two items, the first two items should be a constant as long as the measurement part is strictly specified. Therefore, the size of the above measured values u200bu200bactually reflects the fit quality of the contact surface. . Statistical data show that once the measured value is more than 2 times higher than the normal resistance value, the mating surface is always accompanied by certain defects. It must be noted that it must be recorded and observed or processed. If the interference is less than 0.01mm, the mating surface is rusted, and there are axial cracks in the invisible parts. Of course, the resistance value tested has a certain relationship with the structural size of the bearing, the machining accuracy of the mating surface, and the degree of surface oxidation during use. Therefore, different control values u200bu200bare specified for different types of new and old bearings, and it will take a period of time to measure. to find the correct value. In the process of measurement, especially when there are abnormal values, it is necessary to not only exchange the test leads to measure the average value, but also appropriately increase the number of measurements and positions for accurate judgment. The 'normal resistance value' here is to take the fit interference to meet the requirements of this process, and use the above method to measure (note that the two ends of a bearing should be measured by turning the test leads, a total of 4 measured values), obtain 100 measured values, and then remove Among them, after the extreme value of 5%~10% (belonging to the measurement operation, improper use of the instrument and the actual measurement value of the components that have been in a bad state), calculate the value obtained by the arithmetic mean (note that this measurement value is affected by temperature, it is necessary to need to be corrected). 2. Remove the inner ring and measure the interference amount. Before assembling the removed inner ring or the new bearing inner ring to the shaft, measure the diameter of the inner ring and the shaft, and calculate the interference amount in order to obtain sufficient interference. Earnings. When carrying out this operation, care should be taken to avoid measurement errors caused by measuring values u200bu200bnot under the same temperature conditions (such as measurement locations, different measurement times) and under different measuring tool conditions. It is best to adopt the re-measurement process before assembly, pay attention to the management of measuring tools, record the ambient temperature during measurement, and select the interference according to the process, so that the assembly quality of the bearing inner ring can be reliably guaranteed. 3. Roller measurement grouping is mainly for the case where the statistical value of the roller life has not reached the service life, or when the cage needs to be replaced. It is also suitable for the situation that some rollers are dislodged from the cage and need to be reassembled. The actual measurement results of some units show that the difference between the roller diameters of imported bearings is within 1mm, the international standard stipulates that it is 3mm, and the Chinese standard stipulates that it is 5mm. We are the maintenance department, so we take the latter. The same is true for the measurement of roller length. Obviously, the low matching accuracy is also one of the important reasons for the short service life of domestic bearings. 4. screw torque. The screw tightening should not only be carried out symmetrically, but also should be carried out in two stages according to the torque value. The M6 u200bu200bscrew of the cage is pulled off when it is measured about 17-18N.m, then its yield limit is about 2/3 of the value, that is, 11-12N.m, and then the safety factor is set at 1:1.5, and After rounding, it is 7～8N.m. Its overall safety factor is about 2.25. If the screw is made of good material, its tightening torque can be appropriately increased so that the anti-retarding performance is better. Of course, the tightening torque cannot be increased to the extent that the cage material yields and deforms. 5. After running for a certain period of time, the rolling working surface will always produce a thin layer of fatigue layer (generally less than 10mm in thickness) due to its high contact stress. Surface grinding is carried out when conditions permit to improve the reliability of the bearing. When grinding, the feed amount should not be too large, so as not to cause grinding soft spots. Of course, when the machine tool accuracy in the general locomotive department is not high, it is not suitable to carry out this work, because when the roughness of the machined surface is large, it can destroy the oil film and cause the bearing to heat up and burn. 6. It is stipulated here that the use of technological ferrule instead of measurement is based on the premise that the locomotive depot often does not decompose the inner ring. The accuracy of the bearing is actually composed of dimensional accuracy, shape accuracy and rotation accuracy. Dimensional accuracy refers to dimensional tolerances such as inner, outer diameter and width. The measured value is stipulated in the bearing industry as the average value of the maximum and minimum measured values u200bu200bof the entire circumference, and here is the average value of the measured values u200bu200balong the direction of three equal parts. The difference between the two is not big, and the latter can meet the requirements of maintenance work. accuracy, so unchanged.