Fitting of rolling bearings

Update:11-11-2021
Summary:

1. The choice of cooperation   The inner diameter and o […]

1. The choice of cooperation  
The inner diameter and outer diameter of the rolling bearing are manufactured according to standard tolerances. The tightness of the fit between the inner ring and the shaft, and the outer ring and the seat hole can only be achieved by controlling the tolerance of the journal and the tolerance of the seat hole. The matching of the inner ring of the bearing and the shaft adopts the base hole system, and the matching of the outer ring of the bearing and the seat hole adopts the machine shaft system. Commonly used fits for rolling bearings. To select the fit correctly, it is necessary to know the actual load conditions, operating temperature and other requirements of the bearing, but it is actually very difficult. Therefore, in most cases, the coordination is selected based on the use of fine research.
2. the nature of the load  
When choosing a fit, first consider the rotation of the load vector relative to the ferrule. According to the rotation of the composite radial load vector relative to the ferrule, the composite bearing the ferrule can be divided into: fixed load, rotating load and swing load. a. Fixed load The synthetic radial load acting on the ring is borne by the local area of ​​the ring raceway and transmitted to the corresponding local area of ​​the shaft or bearing seat. This load is called a fixed load. Its characteristic is that the composite radial load vector and the ferrule are relatively static. The ferrule that bears the directional load can choose a looser fit. b. The synthetic radial load acting on the ring by the rotating load rotates along the circumferential direction of the raceway and is borne by various parts in sequence. This load is called the rotating load, and its characteristic is that the synthetic radial load vector is relative to the ring. Spin. The ring bearing the rotating load should be tightly fitted. In special circumstances, such as the load is very light, or the ring only occasionally rotates at a low speed under heavy load, the bearing is selected from harder materials and the surface is rough. The ferrule can also be fitted with a looser fit. c. The direction of the synthetic radial load acting on the ring by the swing load is uncertain. This load condition is called swing load or non-directional load. Its characteristic is that the synthetic radial load vector acting on the ring is fixed on the raceway of the ring. The swing in the area is borne by a certain area of ​​the raceway, or the load acting on the bearing is the load of impact load, vibration load, its direction, and the value often change. Tight fit should be adopted for the fit of the inner and outer ring of the bearing, the state and the bore of the bearing seat under the oscillating load.
3. Load size 
The amount of over gain between the ferrule and the shaft or housing depends on the size of the load. A heavier load uses a larger amount of over gain, and a lighter load uses a smaller amount of over gain. Generally, the equivalent radial load is divided into three conditions: "light", "normal" and "heavy" loads. 4. Selection of tolerance zone for shaft and housing hole 5. Roughness and shape tolerance of the mating surface The roughness and shape tolerance of the mating surface directly affect the performance of the product, such as wear resistance, corrosion resistance and mating properties, etc. Wait. For this reason, rationally stipulating the shape and position tolerances of the shaft and the housing hole and putting forward the requirements of the mating surface roughness are essential for stabilizing the mating properties and improving the coupling strength of the over-win fit.

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