How to install the bearing correctly?

Studies have shown that about 80% of the early failure of bearings is due to incorrect installation. The correct installation of the bearing can not only increase the service life of the bearing and reduce the cost, but also greatly improve the production efficiency. Therefore, it is urgent to learn the correct knowledge of bearing installation.

Bearings are used to support components, but also to support rotating parts on the shaft. The types of bearings are divided according to the friction properties: sliding bearings and rolling bearings; According to the direction of bearing load: radial bearing, thrust bearing, radial thrust bearing, etc. So how to install it correctly?

1、 Assembly of sliding bearing

Sliding bearing is a kind of sliding friction bearing, which is characterized by stable and reliable operation, low noise, and can bear heavy load and large impact load. It can be divided into integral type, split type and tile type according to different structural forms.

1) Assembly of integral sliding bearing

The integral sliding bearing, commonly known as the shaft sleeve, is also the simplest form of sliding bearing. It is mainly assembled by pressing and hammering. In special occasions, the hot assembly method is adopted. Most shaft sleeves are made of copper or cast iron. Care should be taken during assembly. It can be assembled by using wood hammer or hammer pad wood block. When the interference dimension tolerance is large, press in with a press. No matter whether it is knocked in or pressed in, it must be prevented from tilting. After assembly, the oil groove and oil hole should be in the required position.

For the deformed bearing after assembly, the inner hole shall be trimmed. The smaller size can be cut with reamer and the larger size can be scraped. At the same time, pay attention to control the fit clearance with the shaft within the tolerance range. In order to prevent the shaft sleeve from rotating during operation, the contact surface between the shaft sleeve and the box body is equipped with positioning pins or slotted screws. Due to the different hardness of the material of the box and the shaft sleeve, it is easy to make the drill bit deviate to the side of the soft material when drilling. The solutions are as follows: first, punch the hard material side with the sample before drilling, and second, use a short drill bit to increase the rigidity of the drill bit during drilling.

2) Assembly of split bearing

Split bearing, also known as split bearing, has the characteristics of simple structure and convenient adjustment and disassembly. Two bearing shells are embedded on the bearing shells, and the reasonable clearance is adjusted with gaskets at the joint.

① Assembly of bearing bush and bearing body

The upper and lower bearing shells must be in good contact with the bore in the bearing body. If they do not meet the requirements, scrape and grind the back of the bearing shell based on the bore in the bearing body of the thick wall bearing shell, and make the steps at both ends of the bearing shell close to both ends of the bearing body. As long as the split surface of the Thin-walled bearing bush is about 0.1mm higher than that of the bearing body, scraping is not required.

② The bearing bush is installed in the bearing body, and no displacement is allowed in both radial and axial directions. Generally, the steps at both ends of the bearing bush are used for stop positioning or positioning pin positioning.

③ Scraping of bearing bush

Generally, split type bearing shells use the matching bearing grinding points. Generally, the bearing shells are scraped down first and then scraped up. In order to improve efficiency, the bearing shells and covers can not be installed when scraping down the bearing shells. When the contact points of the lower bearing shells basically meet the requirements, the upper bearing shells and covers can be pressed down, and the contact points of the lower bearing shells can be further corrected when scraping up the upper bearing shells. When scraping, the tightness of the shaft can be adjusted by changing the thickness of the gasket with the increase of scraping times. When the bearing cover is fastened, the shaft can rotate easily without obvious clearance, and the scraping is completed when the contact point meets the requirements.

④ Measurement of bearing clearance

The size of bearing clearance can be adjusted by the gasket at the split or by directly scraping the bearing bush. The lead pressing method is usually used to measure the bearing clearance. Take several sections of lead wire with a diameter greater than the bearing clearance and place them on the journal and split surface, then tighten the nut to compress the split surface, unscrew the nut, remove the bearing cover, carefully take out the flattened lead wire, take each section to measure the thickness with a micrometer, and the bearing clearance can be known according to the average thickness of the lead wire. The clearance of general bearing shall be 1.5 ‰ - 2.5 ‰ (mm) of the shaft diameter. When the diameter is large, the smaller clearance value shall be taken. If the shaft diameter is 60mm, the bearing clearance should be between 0.09-0.15mm.

2、 Assembly of rolling bearing

Rolling bearing has the advantages of small friction, small axial size, convenient replacement and simple maintenance.

1) Technical requirements for assembly

① The end face of rolling bearing marked with code shall be installed in the visible direction for checking during replacement.

② The arc radius at the step of journal or shell hole shall be less than that at the corresponding position on the bearing.

③ After the bearing is assembled on the shaft and in the shell hole, there shall be no skew.

④ One of the two coaxial bearings must move with the shaft when it expands.

⑤ When assembling rolling bearings, dirt must be strictly prevented from entering the bearings.

⑥ The assembled bearing must operate flexibly with low noise, and the working temperature should not exceed 65 ℃.