Basic bearing knowledge

As an important part of contemporary machinery, bearings are widely used. We all know and know more or less about it.

Bearings generally consist of an inner ring, an outer ring, rolling elements and a cage. For sealed bearings, add lubricant and seals (or shields). That's what bearings are all about.

According to the working conditions of the bearing, different types of bearings can be selected to better play the function of the bearing and prolong the service life of the bearing. We need to consider the following factors when selecting bearings:

Radial load

Axial load

RPM requirements

Radial runout

Axial runout

Operating temperature

Noise requirements

Lubrication condition

 

The bearing model generally has a pre-code, a basic code and a post-code. In general, the bearing designation is only indicated by the basic designation. The basic model generally consists of three parts, the type code, the size code and the inner diameter code. The post-code is to use letters and numbers to indicate the structure, tolerance and special requirements of the material. The prefix code is used to indicate the sub-components of the bearing, which are indicated by letters.

 

1. Basic codename

The basic code is used to indicate the inner diameter, diameter series, width series and type of bearing, generally up to five digits, as follows:

1) The inner diameter of the bearing is indicated by the first digit from the right of the basic code.

The inner diameter of the bearing with a common inner diameter of d=20~480mm is generally a multiple of 5, and these two digits represent the quotient of the bearing inner diameter size divided by 5, such as 04 means d=20mm; 12 means d=60mm and so on. For bearings with an inner diameter of 10mm, 12mm, 15mm and 17mm, the inner diameter codes are 00, 01, 02 and 03 respectively. For bearings with inner diameters less than 10mm and more than 500mm, the inner diameter representation method is otherwise specified, please refer to GB/T272-93.

 

2) The diameter series of the bearing (i.e., the series of changes in the outer diameter and width of the bearing with the same structure and the same inner diameter) is indicated by the third digit from the right of the basic code.

For example, for radial bearings and radial thrust bearings, 0 and 1 indicate the extra light series; 2 indicates light series; 3 indicates the medium series; 4 indicates a heavy series. The size comparison between the series is shown in the figure below. Except for the extra-light series with 1, the thrust bearing is consistent with the expression of the radial bearing.

3) The width series of the bearing (i.e., the series of changes in the width of the bearing with the same structure, inner diameter and diameter series) is indicated by the fourth digit from the right of the basic code.

When the comparison of the diameter series of the width series of Figure 13-4 is listed as 0 series (normal series), the width series code O can not be marked in the code for most bearings, but for spherical roller bearings and tapered roller bearings, the width series code 0 should be marked. Diameter series codes and width series codes are collectively referred to as dimension series codes.

 

4) The bearing type code is represented by the fifth digit from the right of the basic code (for cylindrical roller bearings and needle roller bearings, the code is a letter).

 

2. Post-code

The post-code of the bearing is to use letters and numbers to indicate the structure, tolerance and special requirements of the material. There are many contents of post-codes, and here are a few commonly used codenames.

1) The internal structure code is to indicate the different internal structure of the same type of bearing, which is indicated by letters followed by the basic code. For example, angular contact ball bearings with contact angles of 15°, 25° and 40° are respectively represented by C, AC and B to represent the difference in internal structure.

2) The tolerance grade of the bearing is divided into 2 grades, 4 grades, 5 grades, 6 grades, 6X grades and 0 grades, a total of 6 grades, in turn from high to low, and their codes are /PZ, /P4, /PS, /P6, /P6X and /PO. Among the tolerance classes, class 6X is only applicable to tapered roller bearings; Grade 0 is an ordinary grade, which is not marked in the wheel bearing code.

3) The commonly used bearing radial clearance series is 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. Group o clearance is a commonly used clearance group, which is not marked in the bearing code, and the rest of the clearance groups are represented by /CI, /CZ, /C3, /C4 and /CS in the bearing code.

 

3. Pre-code

The prefix designation of the bearing is used to indicate the sub-parts of the bearing, which are indicated by letters. For example, L is used to represent the separable ring of a separable bearing; K denotes the rolling elements and cage components of the bearing, etc.

 

There are many types of rolling bearings in practical applications, and the corresponding bearing codes are also more complex. The code introduced above is the most basic and most commonly used part of the bearing code, and you can identify and check the commonly used bearing if you are familiar with this part of the code. For the detailed code method of rolling bearings, please refer to GBT272.