English
Español
Русский
Bearings generally consist of an inner ring, outer ring, rolling elements, and a cage. For sealed bearings, lubricant and seals (or dust covers) are also added. This is the complete composition of a bearing.
Selecting different types of bearings based on their operating conditions is crucial for maximizing their functionality and extending their service life. The following factors should be considered when selecting bearings:
1. Radial load
2. Axial load
3. Speed requirements
4. Radial runout
5. Axial runout
6. Operating temperature
7. Noise requirements
8. Lubrication conditions
Bearing Designations
Bearing designations typically consist of a prefix, a basic designation, and a suffix. Generally, only the basic designation is used. The basic designation usually includes three parts: type designation, size designation, and inner diameter designation. The suffix uses letters and numbers to indicate the bearing's structure, tolerances, and special material requirements. The prefix indicates the bearing's components, represented by letters.
The general method for designating bearings (rolling bearings) is divided into: a prefix, a basic designation, and a suffix.
Basic Designation
The basic designation is used to indicate the bearing's inner diameter, diameter series, width series, and type. It is generally a five-digit designation, described below:
1) The bearing's inner diameter is represented by the first digit from the right of the basic designation. For commonly used bearings with inner diameters d=20～480mm, the inner diameter is generally a multiple of 5. These two digits represent the quotient obtained by dividing the bearing's inner diameter by 5, such as 04 indicating d=20mm; 12 indicating d=60mm, etc. For bearings with inner diameters of 10mm, 12mm, 15mm, and 17mm, the inner diameter designations are 00, 01, 02, and 03 respectively. For bearings with inner diameters less than 10mm and greater than 500mm, the method of representing the inner diameter is specified separately; refer to GB/T272-93.
2) The bearing's diameter series (i.e., the series of bearings with the same structure and inner diameter but variations in outer diameter and width) is represented by the third digit from the right of the basic designation. For example, for radial bearings and radial thrust bearings, 0 and 1 represent the extra-light series; 2 represents the light series; 3 represents the medium series; and 4 represents the heavy series. The dimensional comparison between the series is shown in the figure below. Thrust bearings, except that 1 represents the extra-light series, are represented the same as radial bearings.
3) The width series of bearings (i.e., the series of bearings with the same structure, inner diameter, and diameter series but varying widths) is represented by the fourth digit from the right of the basic designation. When the width series in Figure 13-4 is the 0 series (normal series), the width series designation 0 may be omitted from the designation for most bearings, but for self-aligning roller bearings and tapered roller bearings, the width series designation 0 should be included. The diameter series designation and the width series designation are collectively referred to as the size series designation.
4) The bearing type designation is represented by the fifth digit from the right of the basic designation (for cylindrical roller bearings and needle roller bearings, the type designation is a letter).
Suffix Designations
Bearing suffixes use letters and numbers to indicate the bearing's structure, tolerances, and special material requirements. There are many suffix designations; some commonly used ones are introduced below.
1) Internal Structure Designations: These indicate different internal structures within the same type of bearing, using a letter immediately following the basic designation. For example, angular contact ball bearings with contact angles of 15°, 25°, and 40° are designated C, AC, and B, respectively, to represent different internal structures.
2) Bearing Tolerance Grades: There are six grades: 2, 4, 5, 6, 6X, and 0, from highest to lowest. Their designations are /PZ, /P4, /PS, /P6, /P6X, and /PO, respectively. Grade 6X is only applicable to tapered roller bearings; grade 0 is a standard grade and is not indicated in the bearing designation.
3) Commonly used bearing radial clearance series are divided into six groups: Group 1, Group 2, Group 0, Group 3, Group 4, and Group 5, with radial clearance increasing sequentially. Group 0 clearance is a commonly used clearance group and is not indicated in the bearing designation. The other clearance groups are represented by /CI, /CZ, /C3, /C4, and /CS in the bearing designation, respectively.
Prefix Designation
The prefix designation of a bearing is used to indicate the bearing components, represented by letters. For example, L indicates the separable rings of a separable bearing; K indicates the rolling elements and cage assembly of a bearing, etc.
There are many types of rolling bearings in actual use, and the corresponding bearing designations are quite complex. The designations introduced above are the most basic and commonly used parts of bearing designations. Familiarity with these designations allows for the identification and selection of commonly used bearings. For detailed information on the designation methods for rolling bearings, please refer to GB/T 272-93.
Bearing Selection Methods
The market demands for performance in various mechanical devices and instruments using rolling bearings are becoming increasingly stringent, and the required conditions and performance of bearings are becoming increasingly diverse. To select the most suitable bearing from a large number of structures and sizes, a comprehensive study is necessary. Generally, when selecting bearings, the ease of bearing arrangement, installation, and disassembly within the shaft system, the allowable space and dimensions of the bearing, and the market demand for bearings are considered to roughly determine the bearing structure. Secondly, the design life of various machines using the bearing and the different durability limits of the bearings are compared and studied to determine the bearing size. When selecting bearings, there is often an overemphasis on fatigue life; grease life, wear, and noise caused by grease aging also need to be thoroughly studied. Furthermore, depending on the application, it is necessary to select bearings specially designed for requirements on precision, clearance, cage structure, grease, etc. However, there is no fixed order or rule for selecting bearings; priority should be given to considering the required conditions, performance, and related matters of the bearing, especially practical ones.
Bearing Usage Precautions
Rolling bearings are precision components, and their use must be handled with corresponding caution. No matter how high-performance the bearing, improper use will prevent it from achieving its intended performance. The following precautions should be taken when using bearings:
(1) Keep the bearing and its surrounding area clean.
Even tiny dust particles invisible to the naked eye can negatively impact the bearing. Therefore, keep the surrounding area clean to prevent dust from entering the bearing.
(2) Use with care.
Giving the bearing strong impacts during use can cause scratches and indentations, leading to accidents. In severe cases, it can crack or break, so caution is necessary.
(3) Use appropriate tools.
Avoid substituting existing tools; appropriate tools must be used.
(4) Be aware of bearing corrosion.
Sweat on your hands can cause rust when handling bearings. Always use clean hands, and ideally, wear gloves.
