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Proper Use And Maintenance Of Rolling Bearings


THK Bearings

The rolling bearings consist of an inner ring, an outer ring, a rolling element and a cage. The outer and outer rings of the inner ring have rolling raceways for rolling bodies. The inner ring and the shaft fit, the outer ring and the housing, or the box, the frame hole mates. Usually the inner ring rotates with the shaft, the outer ring does not turn, the outer ring can be rotated and the inner ring does not turn.

Rolling bearings are divided by rolling element: Single ball bearing, roller bearing and needle bearing. According to the direction of bearing load: unidirectional heart bearings, thrust bearings and radial thrust bearings.

The working performance and life of rolling bearings are closely related to the correctness of assembly and maintenance.

First, the assembly of rolling bearings

1, radial ball sleeve bearing

The inner and outer rings of the rolling bearings are thinner and easy to deform during assembly, so the dimensions of the housing bore and shaft must be measured before assembling, so that the bearing can be used in conjunction with the shaft and seat bore to avoid too tight loading.

Clean kerosene or petrol is used to wash the bearings, the shaft neck and the holes with the outer ring of the bearing before assembling. After washing the mating surface to apply some oil, loading must ensure that the rolling element of the bearing is not subjected to pressure? The mating surface is not scratched, the chamfer of the shaft neck or housing bore abutment should meet the requirements. When the bearing is mounted on the shaft, it is not possible to use the hammer to directly tap the bearing outer ring, apply the auxiliary tool, make the force action on the Inner ring by the auxiliary tool (not to allow the outer ring force) if the inner ring is knocked into by tapping the inner ring end face, it will make the inner ring force uneven, easy to tilt, and When the bearing is loaded into the bearing holes, the force should be added to the outer ring of the bearing (the inner ring is not allowed to be subjected to force). If the outer ring is struck by the outer ring, the outer ring is gradually loaded into the hole, which causes uneven force in the outer ring, which causes inclination and scrapes the hole wall. Therefore, auxiliary tools are usually used to force the outer ring, so that the bearing is easy to load and does not damage the rolling bearings and raceways.

The use of auxiliary tools can prevent the installation of dirt into the bearing, and the shaft can withstand reasonable position and uniform, improve assembly quality. Therefore, the assembly of rolling bearings should use auxiliary tools.

The above method is used for occasions where there is little interference. If the interference is large, the assembly of the bearing can be pressed into the method or hot jacket method (The rolling bearing is placed in the oil, mixed oil or water heating. If the bearing cage is plastic, it is only advisable to heat it with water. However, the heat-jacket method cannot be used when the bearing is loaded into the housing bore.

2. Radial Thrust BEARING

The inner and outer rings of the radial thrust roller bearings are separated, and the inner ring and the shaft, the outer ring and the hole are in the same condition as the radial ball bearings. The gap between the inner and outer rings is determined by adjustment after assembly, the gap is too large, the work will vibrate, the gap is too small, then wear faster, easy to heat. The method of clearance adjustment is usually controlled by the axial movement of the outer ring or the axial movement of the inner ring.

3. Thrust ball Bearing (flat bearing)

The thrust bearing consists of a tight ring, a loose ring and a rolling body. The inner hole of the loose ring is larger than the inner hole of the tight ring 0.2mm, when assembling must make the loose ring on the stationary part plane (sometimes its outer circumference and the stationary part match), the tight ring leans on the plane that rotates the part, otherwise, in the bearing and the part produces the sliding friction, the rolling body loses the function, the axis will quickly damage

The clearance of the thrust ball bearing is adjusted by the thread.

Second, the Assembly precautions

1, the rolling bearing is marked with the specifications of the end face should be installed in the visible parts, easy to replace in the future.

2, bearing on the shaft and the bearing seat hole, there should be no skew and stuck phenomenon.

3, in order to ensure that the rolling bearing work has a certain amount of heat expansion in the round shaft of two bearings, there must be an outer ring or inner ring can be in the thermal expansion of the axial movement, so that the shaft or bearing because there is no additional stress, or even in the work to make the bearing bite.

4, strictly avoid copper scraps, iron filings and other impurities into the bearing, the bearing to clean, and sometimes to add some butter, through the sealing cap or sealing ring to prevent oil spills.

5, after assembly, the bearing operation is flexible, no voice, the temperature of the work does not exceed 50 ℃.

6, remove the bearing as far as possible with the puller (pull the horse), the use of the puller should pay attention to the following points:

(1) The two-legged bending angle of the puller can not be greater than 90 °;

(2) Two toes to hook on the plane of the rolling bearing;

(3) When the bearings are split, the two lever are parallel to the screw and cannot be left out;

(4) The screw head of the puller should be made of 90° sharp angle or equipped with a billiard head;

(5) When the puller is used, the distance between the two feet and the screw rod is equal.

Iii. Common mistakes in maintenance

Using compressed air to blow dry the washed bearings is a common method in maintenance. However, some maintenance workers also use high-pressure airflow to blow off the bearings in the dirt, due to the strong impact of compressed air will cause the sudden rotation of the pump, and the rotation of the bearing must go through a period of time sliding before the real pure rolling. This slip can cause noticeable wear and tear, since the cleaned bearing is in a dry friction state without lubricating oil, sliding enough to produce a tiny grinding point on the surface of the rolling element. These tiny grinding points are extremely easy to start in the long run. The correct blow-drying method is to hold the bearing inside and outside the ring at the same time, so as not to slide when suddenly rotating.

When the bearing is loose with the shaft, some maintenance workers use embossing or punching with punch to make the surface of the shaft become hairy, in an attempt to obtain a close mating surface. This does not only destroy the geometry of the shaft surface, so that the bearing in the installation can not get the correct central position and skew, and the final pile of fluff to be flattened and become a loose fit. The correct method of repair is to first grind the shaft neck surface to a layer of metal, then plating the Ming, and then grinding to the required size.

Rolling bearing is a very sophisticated device, very sensitive to foreign bodies, in the maintenance process to maintain a clean and easy to fluff cloth, wipe cloth must not be replaced with old cotton silk, because the old cotton yarn in the head easily mixed with lubricating oil into the bearing, which is very harmful.

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