Installation of bearings

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Bearing installation: 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 grease-lubricated, as well as those 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 should 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 bore, 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 bore. During installation, a fitting sleeve made of a soft metal material (copper or mild 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 structure of the mounting sleeve should be able to compress the end faces of both the inner and outer rings of the bearing 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 hung using hooks; they must not be placed on the bottom of the tank to prevent impurities from getting into 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 should be fixed to the shaft in order to prevent it from rotating relative to the shaft. The method of installing bearings is usually 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