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Installation of Different Types of FAG Bearings

Writer: Eric Bearing Limited

1. Installation of FAG deep groove ball bearings

Deep groove ball bearings have many varieties and specifications, large quantities and wide applications. The installation method is relatively simple, and the cooperation option should be considered. The matching interference between its inner ring and journal can be calculated as follows: 

△d—The amount of interference between the inner diameter of the bearing and the journal (μm)
d—Inner diameter of bearing (mm)
B—bearing width (mm)
R—Bearing radial load (N)
ΔT—The temperature difference between the inside of the bearing and the periphery of the housing hole, generally 5-10℃
After calculation, according to the calculated interference, determine the nature of the fit with the shaft, and then machine the shaft to the required size for installation.

2. Installation of FAG full complement needle roller bearings

The installation of full complement needle roller bearings is usually carried out using auxiliary sleeves. The outer diameter of the auxiliary roller and auxiliary sleeve should be 0.1-0. 3mm smaller than the shaft diameter. When installing, first coat the inner surface of the bearing outer ring with grease, stick the needle against the inner surface (there should be a gap when inserting the last needle), and then use the auxiliary roller instead of the journal or inner ring of the bearing Or push the auxiliary sleeve into the outer ring hole, and align the end face with the end face of the mounting shaft or the end face of the inner ring of the bearing that has been installed on the shaft, and then use a press or a hand hammer to apply pressure. At this time, the auxiliary roller or auxiliary sleeve supports the needle roller to prevent it from falling out, and the journal lifts the needle roller with its own chamfer. As the needle bearing moves slowly inward on the journal, the auxiliary roller Or the auxiliary sleeve will withdraw slowly until it is installed in the working position.
Needle roller bearings can also be installed in this way, that is, apply a thin layer of lubricating oil to the outer diameter of the auxiliary sleeve, insert it into the outer ring of the bearing, so that the auxiliary sleeve and the outer ring of the bearing form an annular hole, and then install needle rollers in the annular hole. After installing the needle roller, use the working shaft to push out the auxiliary sleeve.

For needle roller bearings without inner ring or outer ring, during installation, first apply a thin layer of grease to the rolling surface of the shaft or housing hole, and place the needles on the grease at the installation position in turn. There should be a gap when placing the last needle. The gap should be 0.5mm on the circumference of the needle bearing. Do not squeeze the last needle in hard, or install one less needle, because when hard squeezing, the bearing will be stuck and unable to rotate; when there is less installation, the gap is too large, which will easily cause the bearing to roll during operation. The needle twists and breaks.
It is particularly pointed out here that for needle roller bearings with only a stamped outer ring, because the outer ring wall is very thin, it is best not to hammer and install it, and press in with a press. Because the pressure is uneven when the hand hammer is hit, it is easy to cause local deformation of the outer ring of the needle roller bearing.

3. Installation of FAG tapered roller bearings

FAG tapered roller bearings are separable bearings, and the inner and outer rings can be separated. Therefore, during installation, the inner ring cage rolling element components can be press-fitted on the shaft separately, and the outer ring can be separately installed in the bearing seat hole. When using a sleeve to press-fit, it should be noted that one end of the sleeve must be placed on the end face of the outer ring, and not on the inclined raceway surface.Tapered roller bearings are mostly installed in pairs. Three aspects should be emphasized during installation: choose installation coordination; adjust axial clearance; conduct trial operation and check temperature.
(1) Choose installation coordination
The outer ring of the FAG tapered roller bearing should not adopt interference fit with the housing hole of the bearing seat, and the fit between the inner ring and the journal should not be too tight. It is required that the nut should be used for adjustment in the installation to produce a more flexible axial direction. Displacement. Because the tapered roller bearing adopts interference fit, it is easy to change the contact angle of the bearing, resulting in uneven bearing load distribution and high temperature rise. Therefore, it is best to fit the inner and outer rings of this type of bearing with the shaft journal and the housing hole of the bearing housing. Generally, it is best to just push the bearing into the journal and housing hole with the thumbs of both hands.  FAG HS71913-C-T-P4S-DUL bearings online , pls click here : 
(2) Adjust the axial clearance
For the installation axial clearance of FAG tapered roller bearings, it can be adjusted by the adjusting nut on the journal, the adjusting washer and the thread in the bearing seat hole, or the pre-tensioned spring. The size of the axial clearance is related to the arrangement of the bearing, the distance between the bearings, and the material of the shaft and the bearing seat, and can be determined according to the working conditions. For tapered roller bearings with high loads and high speeds, when adjusting the clearance, the effect of temperature rise on the axial clearance must be considered, and the reduction in clearance caused by the temperature rise must be estimated, that is, the axial clearance It should be appropriately adjusted to be larger. For low-speed and vibration-bearing bearings, clearance-free installation or preload installation should be adopted. Its purpose is to make the rollers and raceways of tapered roller bearings have good contact, and the load is evenly distributed, and to prevent the rollers and raceways from being damaged by vibration and impact. After adjustment, the size of the axial clearance is checked with a dial indicator. The method is to first fix the dial indicator on the body or the bearing seat, make the dial indicator contacts against the smooth surface of the shaft, push the shaft left and right along the axis, the maximum swing of the needle is the axial clearance value.
(3) Carry out trial operation and check temperature
In order to make the rollers of FAG tapered roller bearings have good contact with the raceways and obtain appropriate axial clearances, after the tapered roller bearings are installed and each clearance is adjusted, trial operation and temperature detection should be carried out. The method is to first run at low speed for 2-8 minutes, then test at medium speed for 2 hours, and then gradually increase to high speed. The test run of each speed shall not be less than 30 minutes, the temperature rise rate shall not exceed 5℃ per hour, and the final stable temperature shall not exceed 70℃.
In addition, in the installation and adjustment of the clearance of FAG tapered roller bearings, it should be noted that the tapered rollers must be in good contact with the large ribs of the inner ring.

4. Installation of FAG angular contact ball bearings

The installation of FAG angular contact ball bearings is more complicated than that of deep groove ball bearings. Most of them are installed in pairs and require preload. A good installation can greatly increase the working accuracy of the main engine and the life of the bearing; otherwise, not only the accuracy will not meet the requirements, but the life will be affected.

(1) Installation form
FAG angular contact ball bearings can be installed in three types: back-to-back, face-to-face and tandem arrangement. When installed back to back (the wide end faces of the two bearings are opposite), the contact angle of the bearing spreads along the direction of the rotation axis, which can increase the rigidity of its radial and axial support angles, and has the greatest resistance to deformation; face to face (the narrow end faces of the two bearings are opposite) During installation, the contact angle of the bearing converges in the direction of the axis of rotation, and its ground bearing angle rigidity is small. Since the inner ring of the bearing extends out of the outer ring, when the outer rings of the two bearings are pressed together, the original gap of the outer ring is eliminated, which can increase the preload of the bearing; when installed in series (the wide end faces of the two bearings are in one direction) , The contact angles of the bearings are in the same direction and parallel, so that the two bearings can share the working load in the same direction. However, when using this type of installation, in order to ensure the axial stability of the installation, two pairs of FAG bearings arranged in series must be installed opposite to each other on the shaft.
(2) Obtaining preload
Preloading can be done by grinding the end face of a ring in the bearing, or using two spacers with different thicknesses between the inner and outer rings of a pair of bearings to clamp the bearings together so that the steel ball and raceway Get in close contact.The size of the preload has a great influence on the service life of the bearing. According to relevant information, when the bearing is assembled with 0.012mm interference, the service life is reduced by 38%, and when there is 0.0116mm interference, the service life is reduced by 50%. ; When the bearing is equipped with a gap of 0.004mm, the service life is significantly reduced, and when there is a gap of 0.008mm, the service life is reduced by 70%. Therefore, it is very important to make a reasonable choice of the size of the preload. Generally, a small preload should be selected for high speed, and a large preload should be used for low speed. At the same time, the preload should be slightly greater than or equal to the axial working load.

5. Installation of FAG thrust ball bearings
The shaft ring and the shaft mostly adopt transitional fit, and the seat ring and shaft mostly adopt dynamic fit, and they are often installed in pairs. At the same time, during installation, attention should be paid to check the axial clearance, and the verticality of the shaft ring and the shaft center line rotating with the shaft.