Introduction
The designations of most rolling bearings follow a designation system. The complete bearing designation may consist of a basic designation with or without one or more supplementary prefixes and suffixes. The basic designation identifies: the bearing types the basic design the boundary dimensions Prefixes and suffixes identify design features or bearing components.
Basic Designation
A basic designation typically contains three to five digits. The basic designation system is shown in Figure. The number and letter combinations have the following meaning:
- The first digit or letter or combination of letters identifies the bearing type and eventually a basic variant.
- The following two digits identify the ISO dimension series. The first digit indicates the width or height series (dimensions B, T or H). The second digit identifies the diameter series (dimension D).
- The last two digits of the basic designation identify the size code of the bearing bore. The size code multiplied by 5 gives the bore diameter (d) in mm.
Prefixes and Suffixes
The designations of most rolling bearings follow a system that consists of a basic designation with or without one or more prefixes and/or suffixes.
Prefixes and suffixes provide additional information about the bearing.
Prefixes are mainly used to identify com ponents of a bearing. They can also identify bearing variants.
Suffixes identify designs or variants, which differ in some way from the original design or from the current basic design. The suffixes are divided into groups. When more than one special feature is to be identified.
Most Common Exceptions in Designation System
- In a few cases the digit for the bearing type or the first digit of the dimension series identification is omitted.
- Bearings with a bore diameter of 10, 12, 15 or 17 mm have the following size code identifications: 00 = 10 mm 01 = 12 mm 02 = 15 mm 03 = 17 mm
- For bearings with a bore diameter < 10 mm, or ≥ 500 mm, the bore diameter is generally given in millimetres (uncoded). The size identification is separated from the rest of the bearing designation by an oblique stroke, e.g. 618/8 (d = 8 mm) or 511/530 (d = 530 mm). This is also true for standard bearings in accordance with ISO 15 that have a bore diameter of 22, 28 or 32 mm, e.g. 62/22 (d = 22 mm).
- For some bearings with a bore diameter < 10 mm, such as deep groove, self- aligning and angular contact ball bearings, the bore diameter is also given in millimetres (uncoded) but is not separated from the series designation by an oblique stroke, e.g. 629 or 129 (d = 9 mm).
- Bore diameters that deviate from the standard bore diameter of a bearing are uncoded and given in millimetres up to three decimal places. This bore diameter identification is part of the basic designation and is separated by an oblique stroke, e.g. 6202/15.875 (d = 15,875 mm = 5/8 in).
Bearing Series Identification Codes
Bearing series designations consist of an identification for the bearing type and the dimension series. The most common series designations are shown in table. Codes shown in the below table are the first digit in the bearings numbers from which we can directly identify which type bearing.
| Code | Bearing Type | Code | Bearing Type |
| 0 | Double Row Angular Contact Ball Bearings | 6 | Single Row Deep Groove Ball Bearings |
| 1 | Self-Aligning Ball Bearings | 7 | Single Row Angular Contact Ball Bearings |
| 2 | Spherical Roller / Thrust Bearings | 8 | Cylindrical Roller Thrust Bearings |
| 3 | Taper Roller Bearings | C | CARB Bearings |
| 4 | Double Row Deep Groove Ball Bearings | T | Taper Roller Bearings (ISO 355) |
| 5 | Thrust Ball Bearings | OJ | Four Point Contact Ball Bearings |
| N | Cylindrical Roller Bearings like NU, Nj, NUP, N, NN, NNCF, NNU etc. |
Bearing Designation not covered in the Basic System
Insert bearings: The designations for insert bearings differ somewhat from those described in the basic designation system and are described under Insert bearings.
Needle roller bearings: The designations for needle roller bearings do not fully follow the basic designation system and are described under Needle roller bearings.
Tapered roller bearings: The designations for metric tapered roller bearings follow either the basic designation system or a designation system, established by ISO in 1977, covered in ISO 355. Inch tapered roller bearings are designated in accordance with the relevant ANSI/ABMA standard.
Customized bearings: Bearings designed to meet a specific customer requirement are typically designated by a drawing number. The drawing number does not provide any information about the bearing.
Other rolling bearings: Rolling bearings not covered in the ball bearings and roller bearings sections, such as super-precision bearings, thin section bearings, slewing bearings or linear bearings, follow designation systems that can differ significantly from the basic designation system.
Understanding of Dimension Series
If we are taking example of bearing number NU 2205 and 3205 then dimension series for both the bearing numbers are 22 and 32 respectively and that is different than dimensions for both the bearings are different as shown in the figure besides. There is change in the dimensions in width parameters only as in the dimension series there in the change in width series only. Diameter series for both the bearing are same and i.e. “2”.
If we take same dimension series like hown in the figure besides. For example, if we take bearing number 6205 and NU 205, we have dimensions series for both the bearings are same and i.e. 02. For same dimension series we have bearing dimensions for both the bearing type are same and that is as shown in the figure.
Designation System
Conclusion
From the above information anyone can easily identified the bearing type, its dimension series and bearing dimensions from its number only. There is different type of nomenclature is used by different bearing manufacturer. For the particular bearing number or designation system, please refer manufacturer catalogue only. Further any kind of bearing designation you can contact us on below contact details.
Contact details
KEC Bearings Pvt Ltd
G-2408A, F2 Road, Almighty Gate, Lodhika GIDC, Metoda – 360021, Rajkot, Gujarat (INDIA)
Website: www.kecbearings.com
Email: sales@kecbearings.com
WhatsApp: +91 9330 96 9330
