Method of installing bearings

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The quality of bearing installation affects its precision, lifespan, and performance. Therefore, please conduct thorough research on bearing installation, that is, install the bearings in accordance with the operating standards that include the following items. I. Cleaning bearings and related parts Bearings that are already lubricated with grease, as well as those equipped with oil seals or dust covers on both sides, do not require cleaning before installation. II. Check the dimensions and finish of the relevant parts. III. Installation method: The installation of bearings should be determined based on the bearing’s structure, size, and the nature of the fit between the bearing components. Pressure should be applied directly to the end face of the ring with a tight fit; pressure must not be transmitted through the rolling elements. The following methods are generally used for bearing installation: a. Press-fit: When there is a tight fit between the inner ring of the bearing and the shaft, and a looser fit between the outer ring and the bearing housing hole, a press can be used to install the bearing onto the shaft first. Then, the shaft along with the bearing is inserted into the bearing housing hole. During installation, a fitting sleeve made of a soft metal material (copper or soft steel) is placed on the end face of the inner ring of the bearing. The inner diameter of this fitting sleeve should be slightly larger than the diameter of the shaft journal, while its outer diameter should be slightly smaller than the edge of the inner ring, so as to avoid pressing against the cage. When there is a tight fit between the outer ring of the bearing and the bearing seat hole, and a looser fit between the inner ring and the shaft, the bearing can be pressed into the bearing seat hole first; at this time, the outer diameter of the mounting sleeve should be slightly smaller than the diameter of the seat hole. When the bearing rings are in a tight fit with both the shaft and the housing bore, the inner and outer rings must be pressed into the shaft and housing bore simultaneously; the design of the mounting sleeve should enable the end faces of both the inner and outer rings of the bearing to be compressed at the same time. b. Heating fit　　 A mounting method that converts a tight fit into a loose fit by heating the bearing or bearing housing, utilizing thermal expansion. It is a common and labor-saving installation method. This method is suitable for installing bearings with a large interference fit. Before hot fitting, the bearing or the rings of a separable bearing should be placed in an oil tank and heated evenly to 80–100°C. After that, they are taken out of the oil and installed on the shaft as quickly as possible. To prevent the inner ring surface from not fitting tightly against the shaft shoulder after cooling, axial tightening can be performed once the bearing has cooled down. When the outer ring of the bearing is in tight fit with a bearing housing made of lightweight metal, using a hot mounting method that involves heating the bearing housing can prevent the fitting surfaces from being scratched. When heating the bearings with a oil tank, there should be a grid at a certain distance from the bottom of the tank, or the bearings should be suspended using hooks; they must not be placed on the bottom of the tank to prevent impurities from entering the bearings and to avoid uneven heating. A thermometer must be present in the oil tank, and the oil temperature must be strictly controlled to stay below 100°C, in order to prevent the occurrence of tempering effects that could reduce the hardness of the rings. c. Installation of tapered bore bearings Tapered bore bearings can be installed directly on shafts with a taper, or on the tapered surfaces of set screws and release sleeves. The degree of fit between these components can be determined by the amount of reduction in the bearing’s radial clearance. Therefore, it is necessary to measure the radial clearance of the bearing before installation, and this measurement should be taken frequently during installation until the desired level of clearance reduction is achieved. Locking nuts are generally used for installation, but heating the bearing can also be an alternative method. d. Installation of thrust bearings The fit between the thrust bearing and the shaft is generally a transition fit, while the fit between the bearing ring and the bearing seat hole is usually a clearance fit; as a result, such bearings are easy to install. In the case of dual-thrust bearings, the central shaft portion must be fixed to the shaft in order to prevent it from rotating relative to the shaft. The method of installing bearings is generally such that the shaft rotates; therefore, the fit between the inner ring and the shaft is a tight fit, while the fit between the outer ring of the bearing and the bearing housing is a loose fit. IV. Inspection after bearing installation V. Addition of lubricant Installation of high-speed precision angular contact ball bearings High-speed precision angular contact ball bearings are primarily used in applications involving high-speed rotation with light loads; they require high precision, the ability to operate at high speeds, low temperature rise, minimal vibration, and a certain service life. Often used in pairs as supporting components for high-speed electric spindles, they are key accessories for high-speed electric spindles in internal surface grinders. 　　 Key technical specifications: 　　 1. Bearing precision: Exceeds P4 grade as specified in GB/307.1-94. 　　 2. High-speed performance: dmN value of 1.3~1.8x 106 /min. 　　 3. Average service life: >1500 hours. 　　 The service life of high-speed precision angular contact ball bearings is highly dependent on the way they are installed; the following points should be taken into consideration: 　　 1. Bearing installation should take place in a dust-free, clean environment. The bearings must be carefully selected, and the spacers used with them should be ground. While ensuring that the inner and outer ring spacers are at the same height, their parallelism should be kept within 1um ； 　　 2. Before installing the bearing, it should be cleaned thoroughly. During cleaning, the inclined surface of the inner ring should face upward; the bearing should feel flexible to the touch, with no sense of stiffness. After drying, apply the specified amount of grease; in the case of oil mist lubrication, use a small amount of oil mist lubricant ； 　　 3. Special tools should be used for bearing installation to ensure even force distribution; hitting the bearings is strictly prohibited ； 　　 4. Bearings should be stored in a clean and well-ventilated area free from corrosive gases, with a relative humidity not exceeding 65%; regular rust prevention measures should be taken for long-term storage. Installation of tapered roller bearings and water pump shaft bearings I. Bearing installation: The installation of bearings must be carried out in a dry and clean environment. Before installation, the machining quality of the mating surfaces of the shaft and housing, the end faces of the shoulders, the grooves, and the connection surfaces should be carefully inspected. All mating surfaces must be carefully cleaned and deburred, and the unfinished surfaces of the castings must have all molding sand removed. 　　 Before installation, the bearings should be cleaned thoroughly with gasoline or kerosene, dried before use, and ensured to be properly lubricated. Bearings are generally lubricated with grease, but oil lubrication can also be used. When using lipid lubrication, it is necessary to select grease with excellent properties such as freedom from impurities, oxidation resistance, rust prevention, and extreme pressure protection. The grease filling amount should be 30%-60% of the volume of the bearing and bearing housing; it should not be excessive. The double-row tapered roller bearings with sealing structures and the pump shaft coupling bearings have already been filled with lubricant; they are ready for use by the user and cannot be cleaned further. 　　 When installing the bearing, equal pressure must be applied around the circumference of the ring’s end face in order to press the ring into place; tools such as sledgehammers should not be used to strike the bearing’s end face, as this may damage the bearing. When the interference is small, the end face of the bearing ring can be pressed at room temperature using a sleeve, and the sleeve can be struck with a hammer to evenly press the ring in place. If installing in large quantities, a hydraulic press can be used. During pressing, it is necessary to ensure that the end face of the outer ring is in close contact with the end face of the housing shoulder, and the end face of the inner ring is in close contact with the end face of the shaft shoulder; no gaps are allowed. 　　 When the interference amount is large, bearing installation can be carried out using oil bath heating or inductor heating, with the heating temperature ranging from 80°C to 100°C, and it must not exceed 120°C. At the same time, nuts or other appropriate methods should be used to secure the bearing, in order to prevent contraction of the bearing in the width direction after it cools down, which could create a gap between the ring and the shaft shoulder. 　　 Finally, the clearance of a single-row tapered roller bearing should be adjusted after installation. The clearance value should be determined specifically based on different operating conditions and the amount of interference in the fit. If necessary, tests should be conducted to determine this. Double-row tapered roller bearings and pump shaft coupling bearings have their clearances adjusted at the time of manufacture, so no further adjustment is required during installation. 　　 After the bearing is installed, a rotation test should be conducted. First, it is tested on the rotating shaft or bearing housing; if there are no abnormalities, it is then operated at low speed without load using power. Thereafter, the rotation speed and load are increased gradually depending on the operating conditions, while noise, vibration, and temperature rise are monitored. If any abnormalities are detected, operation should be stopped for inspection. It can be put into use only after the operation test is successful. 　　 II. Removal of bearings: When bearings are removed and intended to be used again, appropriate removal tools should be selected. To remove a ring that is in an interference fit, tension can only be applied to that ring; it is absolutely not allowed to use the rolling elements to transmit the removal force, otherwise both the rolling elements and the raceways will be damaged. 　　 III. Operating environment of bearings: Selecting the appropriate specifications and precision based on the location of use as well as the operating and environmental conditions is a prerequisite for ensuring the lifespan and reliability of bearings. 　　 1. Application areas: Tapered roller bearings are suitable for withstanding combined radial and axial loads, with radial loads being the predominant type. They are usually used in pairs, and find application in transmission components such as the front and rear wheel hubs of vehicles, driving bevel gears, differentials, and reducers. 　　 2. Allowable speed: Under proper installation and optimal lubrication conditions, it may be 0.3–0.5 times the bearing’s maximum allowable speed. Under normal circumstances, 0.2 times the maximum speed is the most suitable. 　　 3. Allowable tilt angle: Cylindrical roller bearings generally do not permit any tilt of the shaft relative to the housing bore; if such a tilt does occur, it should not exceed 2′. 　　 4. Allowable temperature: Under normal load conditions, with a lubricant that has high-temperature resistance and adequate lubrication, bearings can generally operate in an ambient temperature range of -30°C to 150°C. This post was last edited by zgj2405 on 2008-12-21 11:42.]