In simple terms, bearing clearance is the clearance (or interference) within a single bearing, or within a system composed of several bearings. Clearance can be divided into axial clearance and radial clearance, depending on the bearing type and measurement method.

Why adjust the bearing clearance

For example, too much or too little water during cooking 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 suitable for different adjustment methods

The method of clearance adjustment is determined by the type of bearing, which can generally be divided into non-adjustable bearings and adjustable bearings.

A bearing with non-adjustable clearance means that the clearance of the bearing is determined after the bearing leaves the factory. The well-known deep groove ball bearing b self-aligning bearing and cylindrical bearing 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 belong to this category are tapered bearings and angular contact ball bearings and some Thrust bearing.

Bearing clearance adjustment classification

For the clearance of non-adjustable bearings, the industry has corresponding standard values u200bu200b(CN, C3, C4, etc.), and can also customize specific clearances Scope. 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 selection of the optimum working clearance is determined by the application conditions (load, speed, design parameters) and the expected working conditions (maximum life, best stiffness, low heat generation, ease of maintenance, etc.). 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.

How to adjust the clearance of tapered roller bearings

The clearance of non-adjustable bearings after installation is mainly affected by the fit. The following mainly introduces the clearance of adjustable bearings. The gap adjustment method is taken as an example of a tapered roller bearing that is suitable for a wide range of rotation speeds and can withstand both axial and radial forces.

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, push it to the end, set the dial indicator to zero for reference, and then apply a force in the opposite direction, after pushing 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, the deformation of an elastically deformed object is proportional to the external force it is subjected to . 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 is suitable for positive clearance and preload, operators need to be trained to create charts.

3.Torque-SetTM method

The principle of Torque-Set is that under preload, the increase of the rotational torque 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 b 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 by testing. Then, during the actual installation, the thickness of the gasket can be determined by measuring the rotational torque.

4.Projecta-SetTM method

Projecta-Set is to project or convert the thickness of the gasket or spacer that cannot be measured directly to a place where it is easy to measure. This can be achieved using a 2 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 expensive. 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 related parts to ensure that 99.73% of all assemblies have bearings Clearance is within acceptable limits. 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 simple to assemble and clamp, so it is very convenient to install in large quantities. 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.