Most bearing damage can be caused by incorrect bearing installation

In fact, 80% of bearings fail early because they are not installed correctly. The correct installation of the bearing can not only increase the service life of the bearing, reduce the cost, but also greatly improve the production efficiency. Therefore, it is urgent to learn the correct bearing installation knowledge. Bearings are used to support components and also to support rotating parts on the shaft. The types of bearings are classified according to friction properties: sliding bearings and rolling bearings; According to the direction of bearing load, there are radial bearings, push bearings, radial thrust bearings, etc.

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

(1) Assembly of integral sliding bearing

Integral sliding bearing, commonly known as shaft sleeve, is also a simple form of sliding bearing. It is mainly assembled by pressing and hammering. In special occasions, hot assembly method is used. Most shaft sleeves are made of copper or cast iron. They should be assembled carefully. They can be assembled by striking with a wooden hammer or a wooden block with a hammer. When the interference size tolerance is large, press them with a press. No matter knocked in or pressed in, the inclination must be prevented. After assembly, the oil groove and oil hole should be at the required position.

The deformed bearing after assembly shall be trimmed. The smaller bearing can be reamed, and the larger bearing can be scraped. At the same time, pay attention to control that the fit clearance with the shaft is 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 is equipped with a locating pin or a slotted screw. Because the hardness of the box and shaft sleeve materials is different, it is easy to make the drill bit incline to the soft material side when drilling. The solution is: first, punch the hole against the hard material with a sample before drilling, and second, use a short drill bit to increase the rigidity of the drill bit when drilling.

(2) Assembly of split bearing

Split bearing, also known as split bearing, has the characteristics of simple structure, easy adjustment and disassembly. Two bearing pads are inserted on the bearing pads, and a gasket is used at the joint to adjust the reasonable clearance.

① Assembly of bearing bush and bearing body

The upper and lower bearing pads must be in good contact with the bore in the bearing body. If they do not meet the requirements, the bore in the bearing body of the thick wall bearing pad shall be taken as the benchmark, and the back of the bearing pad shall be scraped. At the same time, the steps at both ends of the bearing pad shall be close to both ends of the bearing body. The thin wall pad only needs to make the split of the bearing pad about 0.1mm higher than the split of the bearing body, and it is unnecessary to scrape.

② When the bearing bush is installed in the bearing body, no displacement is allowed in the radial or axial direction. The steps at both ends of the bearing bush are usually used to stop or locate the bearing bush.

③ Scraping of bearing bush

In general, the matched bearing lapping points are used for split bearing pads. Generally, the lower bearing pads are scraped first, and then the upper bearing pads are scraped. In order to improve efficiency, the bearing pads and covers can not be installed when the bearing pads are scraped off. When the contact points of the lower bearing pads basically meet the requirements, the upper bearing pads and upper covers can be pressed tightly, and when the upper bearing pads are scraped, the contact points of the lower bearing pads can be further corrected. When scraping, the tightness of the shaft can be adjusted by changing the thickness of the gasket with the increase of scraping times. After the bearing cover is fastened, the shaft can rotate easily without obvious clearance, and the scraping can be 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 obtained by directly scraping the bearing bush. The bearing clearance is usually measured by the lead pressing method. Take several pieces of lead wire with a diameter greater than the bearing clearance, place them on the journal and the split, tighten the nut to make the split tight, then unscrew the nut, take down the bearing cover, carefully take out the flattened lead wire, and use a micrometer to measure the thickness of each section. The bearing clearance can be known according to the average thickness of the lead wire. The clearance of general bearings shall be 1.5 ‰ - 2.5 ‰ (mm) of the shaft diameter, and the smaller clearance value shall be taken when the diameter is larger. If the shaft diameter is 60mm, the bearing clearance shall be between 0.09-0.15mm.