Bearing installation error demonstration and correct installation method

Many people are unfamiliar with the bearing, so when installing the bearing, because they are not able to fully understand the bearing installation method, it may lead to the wrong installation of the bearing, resulting in damage to the bearing during the operation of the bearing. To list the common bearing installation error events and the corresponding bearing correct installation method.

Bearing installation error cases:

1. Go inside

Loose fit between shaft and bearing bore

Because the fit between the shaft and the inner hole is too loose, the surface of the shaft and the inner hole will slide. Sliding friction will cause heating and damage the bearing due to heating.

There are traces of sliding between the shaft and the surface of the inner hole

Inner ring end face and shaft shoulder friction heating cracks

When "walking the inner ring", the sliding friction between the inner ring and the shaft will produce high temperature. Because the contact surface between the inner ring end face and the shaft shoulder is very small, the temperature will be higher. The inner ring end face will produce hot cracks, and the continuous extension of hot cracks will make the bearing inner ring fracture in use.

The adhesion between the shaft and the surface of the inner hole occurs after heating.

Due to the sliding friction between the inner hole and the shaft surface caused by "walking inner ring", the surface metal melts and adheres due to the high temperature.

2. Go outside

Loose fit between shell hole diameter and bearing outer diameter (commonly known as "outer ring")

Due to the loose fit between the bore diameter of the shell and the outer diameter of the bearing, sliding occurs between their surfaces. Sliding friction will cause heating and damage the bearing.

There are traces of sliding between the bore diameter of the shell and the surface of the outer diameter of the bearing

3. The hammer strikes the bearing directly

When installing the bearing with inner ring (or outer ring) interference fit, it is forbidden to directly knock the end face of bearing inner ring (or outer ring) with hammer, which is easy to damage the rib. The sleeve should be placed on the end face of the inner ring (or outer ring) and installed by knocking the sleeve with a hammer.

4. The installation force is transmitted through the rolling element

When installing the bearing with inner ring interference fit, the force cannot be transferred to the inner ring through the outer ring and rolling element. This will damage the surface of bearing raceway and rolling element, and make the bearing produce noise and damage in advance. The correct way is to use the sleeve to directly apply the force on the inner ring end face.

5. Heating temperature too high

When the heating temperature exceeds 727 ℃, the metallographic structure of the bearing steel will change. When the bearing is cooled, the bearing bore cannot be restored to its original size, which is usually larger than that before heating.

The surface of the bearing heated by acetylene spray gun turns black.

Correct method of bearing installation:

Whether the bearing is installed correctly affects the accuracy, life and performance. Therefore, the design and assembly department should fully study the bearing installation.

The bearing should be installed in a dry and dust-free area as far as possible, and away from the equipment that will produce metal debris and dust. When it must be installed in a complex environment, the pollution should be reduced. When installing bearings, mechanical, heating or hydraulic methods should be selected according to the type and size.

Installation of cylindrical bearing

Cold installation

When installing a small bearing that is not too tight, you can use a sleeve and hammer to gently knock the sleeve to install the bearing in a suitable position. When knocking, it should act on the bearing ring as evenly as possible to prevent the bearing from tilting or skewing.

Most bearings are installed by hot pressing

In general, for the installation of larger bearings, it is not possible to heat the bearing or bearing seat, because with the increase of size, the greater the force required for installation. The temperature difference between the bearing ring and the shaft or bearing seat for hot installation mainly depends on the interference and the diameter of the bearing fit.

The heating temperature of open bearing shall not exceed 120 ℃. It is not recommended to heat the bearing with seal and dust cover above 80 ℃.

When heating the bearing, it should be heated evenly, and there must be no local overheating.

Bearing induction heater

Installation of tapered bearing

Most of the inner rings of bearings with tapered holes are installed by interference fit. The amount of interference is determined by the axial pushing distance of the inner ring on the conical shaft diameter, tightening sleeve or stripping sleeve. The larger the advancing distance on the conical mating surface, the smaller the radial internal clearance of the bearing. The interference can be determined by measuring the clearance reduction or axial advancing distance.

Small and medium sized bearings can use bearing installation tools or lock nuts to push the inner ring to a proper position on the conical shaft diameter. In the case of using tightening sleeve, use socket nut which can be locked by hook wrench or impact wrench. The sleeve can be pushed into the bearing bore with bearing installation tool or end plate

Larger bearings require more force to install, so hydraulic nuts should be used. The hydraulic nut can install the tapered hole bearing on the conical shaft diameter, the tightening sleeve and the withdrawing sleeve.

Oiling method

The working principle of oil injection method is: under high pressure, hydraulic oil is injected into the matching surface between bearing and shaft diameter through oil hole and oil groove to form an oil film. The oil film separates the mating surfaces, which greatly reduces the friction between the mating surfaces.

This method is usually used to install the bearing directly on the conical shaft diameter. The necessary oil holes and grooves shall be part of the integral shaft design. This method can also be used to install the bearing on the tightening sleeve or the withdrawal sleeve if the tightening sleeve and the withdrawal sleeve have oil holes and grooves.