Bearing assembly principles, installation precautions, models and their meanings

Bearings are an important part of contemporary machinery and equipment, and their usage is staggering. Taking a car as an example, a car generally needs 100 to 150 bearings to ensure normal driving. The main function of the bearing is to support the mechanical rotating body, reduce the friction coefficient during the movement, and at the same time ensure its rotation accuracy. my country's bearing industry is developing rapidly, bearing varieties from few to many, product quality and technical level from low to high, the industry scale from small to large, has formed a professional production system with basically complete product categories and a relatively reasonable production layout. Today, the editor of Xianji.com will come to talk about the relevant knowledge about bearings, including: bearing assembly principles, installation notes, models and their meanings. Let's take a look!
 
Bearing assembly principle
 
Preparation before assembly
1. Preparation of measuring tools and tools.
2. Inspection of parts: such as the processing quality inspection of shafts, housings, end caps, bushings, sealing rings and other parts. The surface matched with the bearing should not have depressions, burrs, rust and solid particles.
3. Cleaning of parts: Before installing the bearing, use diesel or kerosene to clean the shaft, housing and other parts, and wipe the surface with a clean cloth (not cotton yarn), and then apply a thin layer of oil to facilitate installation. All lubricating oils are cleaned and inspected to ensure smoothness.
4. Cleaning of bearings: Bearings sealed with anti-rust oil can be cleaned with diesel or kerosene; bearings with dust caps or seal rings on both sides have been added with lubricants before leaving the factory, as long as the lubricants in the bearings are not damaged or deteriorated , The bearings can be installed without cleaning; bearings coated with anti-rust and lubricating grease can also be cleaned during installation. The bearing should be filled with lubricant immediately after cleaning, and the bearing should be turned slowly when oiling, so that the grease enters between the rolling body and the raceway. The lubricating oil (grease) for bearings must be clean and free of dirt.
 
Overhaul of shaft and bearing seat
1. Overhaul of the shaft: first check whether it is bent or deformed with a dial indicator. If there is any deformation, it should be turned, grinded or straightened. There should be no burrs or bumps on the mating surface of the shaft and the bearing, the perpendicularity of the shaft shoulder to the shaft, and the radius of the corner of the shaft shoulder should be measured.
2. Maintenance of bearing housing hole: measure the roundness and cylindricity of the bearing housing hole, check the verticality of the shaft shoulder of the bearing housing hole, etc.
 
Assembly of rolling bearings
1. Bearings with tight fit between the inner ring and the shaft, and loose fit between the outer ring and the bearing seat, the hammered end face of the assembly sleeve should be processed into a spherical shape. Where there is no press or where the press cannot be used, the bearing can be installed with an assembly sleeve and a hammer.
2. The inner ring is loosely fitted with the shaft, and the outer ring is tightly fitted with the bearing seat for bearing installation. Press the bearing into the bearing seat first, the outer diameter of the assembly sleeve should be slightly smaller than the diameter of the shell hole, and then install the shaft.
3. The inner ring and the shaft, the outer ring and the bearing seat are installed with tight-fitting bearings. The end face of the assembly sleeve should be processed into a ring that can simultaneously compress the inner and outer ring end faces of the bearing to press the bearing into the shaft and the bearing seat hole. This method is suitable for the installation of self-aligning radial ball bearings.
4. Hot (cold) assembly method of bearings. Before hot assembly, put the bearing or separable bearing ring into the oil and heat it evenly to 80~100℃ (should not exceed 100℃), then take it out and install it on the shaft quickly.
5. Disassembly of rolling bearings. Rolling bearings adopt the hot assembly method, cold assembly method and hot unloading method. The advantage is that the interference will not be damaged, and the assembly and disassembly are both labor-saving and rapid.
 
 
Bearing installation considerations
1. Avoid hard mounting and impact, you must ensure that the bearing is gently installed, and the bearing and the seat hole have a small clearance. Normally, you should tap the end face to install it in a normal position. The hole surface was injured or even scrapped.
2. The bearing inner sleeve must be heated by induction and must not exceed 120°C. It is strictly forbidden to disassemble and assemble bearings by open flame.
3. When it is not easy to install, find out the reason, take reasonable measures after eliminating the problem, and timely repair when there are problems such as parts deformation, and if necessary, please revise the drawings.
4. Inject sufficient and clean grease in strict accordance with requirements.
5. When unqualified seals, glands and other parts are found in the installation, they must be strictly scrapped or repaired to ensure that the assembly quality meets the quality requirements.
 
 
Bearing model and its meaning
 
Basic code
The basic code is used to indicate the inner diameter, diameter series, width series and type of the bearing, generally up to five digits, first described as follows:
1. The inner diameter of the bearing is indicated by the first digit from the right of the basic code. For bearings with a common inner diameter d=20～480mm, the inner diameter is usually a multiple of 5. These two digits represent the quotient of the bearing inner diameter divided by 5, for example, 04 means d=20mm; 12 means d=60mm and so on. For bearings with inner diameters of 10mm, 12mm, 15mm and 17mm, the inner diameter codes are 00, 01, 02 and 03 in sequence. For bearings with an inner diameter of less than 10mm and greater than 500mm, the method for expressing the inner diameter is otherwise specified, see GB/T272-93.
2. The diameter series of bearings (that is, the series of changes in the outer diameter and width of bearings with the same structure and the same inner diameter) is represented by the third digit from the right of the basic code. For example, for radial bearings and radial thrust bearings, 0 and 1 indicate extra light series; 2 indicates light series; 3 indicates medium series; 4 indicates heavy series. The size comparison between each series is shown below. Thrust bearings are identical to those of radial bearings except that 1 represents the extra light series.
3. The width series of the bearing (that is, the series of changes in the width of the bearing with the same structure, inner diameter and diameter series) is represented by the fourth digit from the right of the basic code. When the comparison of the width series of Figure 13-4 diameter series is 0 series (normal series), for most bearings, the width series code O may not be marked in the code, but for spherical roller bearings and tapered roller bearings, the width series The code 0 should be marked. The diameter series code and the width series code are collectively called the size series code.
4. The bearing type code is represented by the fifth digit from the right of the basic code (the type code for cylindrical roller bearings and needle bearings is letters).
 
Post code
The post code of the bearing indicates the structure, tolerance and special requirements of the material with letters and numbers. There are many contents of the post code, the following introduces several commonly used codes.
1. The internal structure code refers to different internal structures of the same type of bearing, and the letter follows the basic code. For example: angular contact ball bearings with contact angles of 15°, 25° and 40° use C, AC and B to indicate the difference in internal structure.
2. The tolerance class of the bearing is divided into 2 levels, 4 levels, 5 levels, 6 levels, 6X levels and 0 levels, a total of 6 levels, from high to low level in turn, and their code names are /PZ, /P4, /PS, /P6, /P6X and /PO. In the tolerance class, the 6X class is only applicable to tapered roller bearings; the 0 class is an ordinary class and is not marked in the wheel bearing code. .
3. The commonly used radial clearance series of bearings are divided into 1 group, 2 groups, 0 groups, 3 groups, 4 groups and 5 groups, a total of 6 groups, and the radial clearance is from small to large in turn. O group clearance is a commonly used clearance group, which is not marked in the bearing code, and the remaining clearance groups are represented by /CI, /CZ, /C3, /C4, /CS in the bearing code.
 
Prefix
1. The front code of the bearing is used to indicate the sub-components of the bearing, and is represented by letters. For example, L means the separable ring of the separable bearing; K means the rolling element and cage assembly of the bearing and so on.
2. There are many types of rolling bearings used in practice, and the corresponding bearing codes are also relatively complicated. The code introduced above is the most basic and commonly used part of the bearing code. If you are familiar with this part of the code, you can identify and select the commonly used bearings.