What is bearing clearance? In simple terms, bearing clearance is the clearance (or interference) within a single bearing, or within a system of several bearings. Clearance can be divided into axial clearance and radial clearance, depending on the bearing type and measurement method. Why adjust bearing clearance? For example, too much or too little water when cooking rice will affect the taste of the rice. In the same way, if the bearing clearance is too large or too small, the working life of the bearing and even the stability of the entire equipment operation will be reduced. Types of Bearings Applicable to Different Adjustment Methods The method of clearance adjustment is determined by the type of bearing, which can generally be divided into non-adjustable clearance bearings and adjustable bearings. The bearing with non-adjustable clearance means that the bearing clearance is determined after the bearing leaves the factory. The well-known deep groove ball bearings, self-aligning bearings and cylindrical bearings belong to this category. Adjustable clearance bearing means that the relative axial position of the bearing raceway can be moved to obtain the required clearance, which includes tapered bearings, angular contact ball bearings and some thrust bearings. Classification of bearing clearance adjustment For the clearance of non-adjustable bearings, the industry has corresponding standard values ​​(CN, C3, C4, etc.), and can also customize specific clearance ranges. When the dimensions of the shaft and bearing seat are known, the corresponding fit of the inner and outer rings is determined, and the clearance after installation cannot be changed. Since the fit amount is a range in the design stage, there is also a range for the final clearance, which is not suitable for applications that require clearance accuracy. Adjustable bearings solve this problem very well. By changing the relative axial position of the raceway, we can get a certain clearance value. As shown in the figure below, when moving the position of the inner ring, we can roughly get positive and negative clearances. Factors Affecting Bearing Clearance The choice of the optimum working clearance is determined by the application conditions (load, speed, design parameters) and the desired working conditions (maximum life, best stiffness, low heat generation, ease of maintenance, etc. etc.) decided. However, in most applications, we cannot directly adjust the working clearance, which requires us to calculate the corresponding post-installation clearance value based on the analysis and experience of the application. Adjustment method of the clearance of tapered roller bearings The clearance of non-adjustable bearings after installation is mainly affected by the fit, so the following mainly introduces the adjustment methods of the clearance of adjustable bearings, so as to be suitable for a wide range of rotation speeds, and can withstand axial force and diameter at the same time. Take force-oriented tapered roller bearings as an example. 1 Push-pull method The push-pull method is generally used for positive clearance, and the axial clearance between the bearing raceway and the rolling elements can be measured. Apply a force to the shaft or bearing seat in one direction, set the dial indicator to zero for reference after pushing it to the end, and then apply a force in the opposite direction, after pushing it to the end, the rotation of the pointer on the dial indicator is the clearance value. When measuring, rotate the roller slowly to ensure that the roller is correctly positioned on the large rib of the inner ring. 2 Acro-SetTM method The theoretical basis of Acro-Set is Hooke's law, and the deformation amount of the elastically deformed object is proportional to the external force. Under a certain installation force, measure the gasket or spacer clearance to obtain the correct clearance. Read directly the correct shim or spacer size required according to a chart created during a prior test. This method works for positive clearance and preload, and operators need to be trained to create the charts. 3 Torque-SetTM method The principle of Torque-Set is that under preload, the increase of the rotational moment of the bearing is a function of the bearing preload. The experimental results show that for a group of new bearings of the same type, under the condition of a given preload, the change in the rotational moment of the bearing is very small. Therefore, the torque can be used to estimate the amount of preload. The principle of this method is to establish a conversion relationship between the rotational torque of the bearing and the preload, which needs to be obtained through testing. Then, during the actual installation, the thickness of the gasket can be determined by measuring the rotational torque. 4Projecta-SetTM method Projecta-Set is to project or convert the thickness of the gasket or spacer that cannot be directly measured to a place where it is easy to measure. This can be achieved using a special gauge sleeve and spacer. When the inner and outer rings of the bearing are in a tight fit condition, the removal and adjustment of the bearing can be difficult and time-consuming. At this time, Projecta-Set reflects its advantages. This method requires separate gauges for different series of bearings, which is relatively costly. But when it comes to mass installations, the average per-time cost is good. Especially in the field of automation, it has proven to be a very effective method. 5 Set-RightTM Method Set-Right uses a probabilistic method and controls the dimensional tolerances of the relevant parts to ensure that 99.73% of the bearing clearance in all assemblies falls within the acceptable range. This is a mathematical prediction combined with a set of random variables. The variables are bearing tolerances and tolerances of mounted components such as shafts and housings. This method does not require installation and adjustment, and the application components are simply assembled and clamped.Therefore, mass installation is very convenient. But in the end there will be a range of clearance (about 0.25mm), and whether Set-Right can be used in some applications needs to be decided at the design stage. The Set-Right method has been used successfully for many years, both in industry and in the automotive field. (Source: Bearing Encyclopedia)