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The Ultimate Guide to Bearing Numbers
Bearing numbers provide guidance in identifying bearing type, typical use, durability and suitability. No matter what brand of bearing you buy, as long as you understand the meaning of the standard bearing number, you can accurately identify the bearing you need. It’s worth noting that bearing numbers are not universally standardized and may vary from brand to brand. As China’s top bearing manufacturer and supplier, we believe it is necessary to train non-technical personnel with bearing needs. Today we will discuss bearing numbers to identify bearings.
Bearings are used in a wide range of mechanical equipment and comply with standardized designs and international regulations. Most bearings will contain identification markings. These markings are usually a series of numbers and letters, and identifying bearing numbers can sometimes be complicated. The American Bearing Manufacturers Association (ABMA), an industry trade group founded in 1917 as a committee of the world’s leading bearing manufacturers, developed the standard numbering code as a universal identifier for bearing dimensions and properties. The main purpose of ABMA is to define bearing-related standards and maintain industry-related statistics. This standardization helps end users and distributors interchange bearings from other manufacturers when necessary. Engineers can use this code to configure a bearing with the features required for their specific application (for example, a stainless steel deep groove ball bearing with metal seals on each side).The ABMA code applies to ball bearings (including Conrad type, maximum capacity and angular contact bearings) as well as cylindrical rollers, spherical rollers and thrust ball or roller bearings.
International bodies such as ABMA, ISO and ANSI standardize some bearing regulations, but they also leave room for bearing manufacturers to innovate and develop uniquely designed bearings to help differentiate themselves from other manufacturers. As such, there are no strict standards for bearing part numbers, resulting in each bearing manufacturer having a unique part numbering scheme. Bearings are a perfect example of a highly engineered commodity whose nature allows them to be interchanged from one manufacturer to another and ensures that they have the same dimensions, features, and operating specifications.
When a supplier uses its own numbering system and is not interchangeable with other suppliers, most suppliers will provide a cross-reference to the ABMA code standard. For example, Aubearing provides ABMA to Aubearing product number conversion. Users can convert between AMBA and Aubearing and vice versa. Using this type of conversion, engineers can convert bearing numbers from one manufacturer to ABMA and then to another manufacturer as needed. Many manufacturers also produce non-standard bearings with unique or special functions or characteristics. These bearings are not technically a commodity as they are not necessarily interchangeable with other products and may not be converted to ABMA standard numbering conventions. If a manufacturer chooses to use its own numbering system, end users must rely on bearing interchange information provided by the manufacturer or distributor. Aubearings, for example, offers cross-referencing and bearing exchanges on its website.
What is a bearing number?
The series of numbers and letters in a bearing number may seem confusing, consisting of several paragraphs, each providing specific information about the bearing. Typically, a bearing number consists of three distinct parts: prefix, base name and suffix. The bearing number indicates the specifications of the bearing, including bearing type, overall dimensions, running accuracy and internal clearance. This is true for the ABMA bearing codes as well as the codes used by Aubearing, which is similar to the numbering system used by many other manufacturers. Take NTN deep groove ball bearing code “TS2-6206 x1 LLB N C3 P5/2AS” as an example:
“TS2” stands for the prefix meaning “thermal stable up to 320°F (160°C)”;
“6206” is the basic code of the bearing – digital identification;
‘X1’, ‘LLB’, ‘C3’, ‘P5′, 2AS’ are suffixes.
Some bearings are identified only by a numerical code without any prefix or suffix, such as bearing “6203”.
Some bearings only have a suffix, such as “6203 LLB C3 P5”.
Bearing number composition
Prefix
The prefix mainly indicates a specific component of the bearing, but may also identify various bearing variants. Let’s take the NTN prefix as an example.
In terms of thermal stability:
Prefix | Implication |
No Prefix | Heat stabilized up to 250°F (120°C) |
TS2 | Heat stabilized up to 320°F (160°C) |
TS3 | Heat stabilized up to 390°F (200°C) |
TS4 | Heat stabilized up to 480°F (250°C) |
5S | Ceramic rolling elements |
7MC3 | MEGAOHM® (ceramic coating) |
In terms of materials:
Prefix | Implication |
No Symbol | High carbon chrome bearing steel (equivalent to AISI E52100) |
F | Martensitic stainless steel (equivalent to AISI 440C) |
N | Beryllium Copper |
For SKF, its deep groove ball bearing code prefixes such as:
Prefix | Implication |
D/W | D/W |
ICOS- | Oil sealed bearing unit |
W | Stainless steel, metric dimensions |
WBB1 | Stainless steel, metric dimensions, not in accordance with ISO dimension series |
Bearing first number
The first number in the bearing number is significant because it usually indicates the type of bearing. It helps determine the core design of the bearing. For example, in “6206”, the first number “6” means “single row deep groove ball bearing”. The table below lists the various types of bearings and their type codes.
Bearing Type | SKF | NSK | Timken | FAG |
Double row angular contact ball bearing | 0 | 3,5 |
| 3 |
Self-aligning ball bearing | 1 | 1 | 1,2 | 1 |
Spherical roller bearing, spherical roller thrust bearing | 2 | 2 | 2 | 2 |
Tapered roller bearing | 3 | 3 | 3 | 3 |
Double row deep groove ball bearing | 4 | 4 |
| 4 |
Thrust ball bearing | 5 | 5 | 5 | 5 |
Single row deep groove ball bearing | 6 | 6 | 6 | 6 |
Single row angular contact ball bearing | 7 | 7 | 7 | 7 |
Cylindrical roller thrust bearing | 8 |
| 8 |
|
CARB toroidal roller bearing | C |
|
|
|
Cylindrical roller bearing | N | NU, N, NU, NN | NU, NN, N, NF | N, HCN, NN, NNU |
Four-point contact ball bearing | QJ |
|
| QJ |
Tapered roller bearing in accordance with ISO 355 | 00 | 01 | 02 | 03 |
Separable ball bearing |
| BO, E, L |
|
Bearing second number
The second number in the bearing number usually indicates the bearing series. It reflects the robustness of the bearing, with the number indicating the light, medium or heavy series. Therefore, this number can give you insight into the bearing’s ability to handle different loads. For example, in “6 2 0 6”, the second number “2” means “very thin part”.
Series Code | Series Description |
0 | Extra Light |
1 | Extra Light Thrust |
2 | Light |
3 | Medium |
4 | Heavy |
8 | Extra Thin Section |
9 | Very Thin Section |
The third and fourth number of the bearing number
The third and fourth number in the bearing number are important because they usually represent the bearing’s inner diameter (ID) in millimeters. They provide important information about the fit of the bearing to the shaft on which it is mounted.
The bore diameter in the bearing number ranges from 0 to 3, which means 10 to 17 mm.
For numbers above “03”, the bore size is calculated as 5 times the value represented by the 3rd and 4th digits in the bearing number.
For example, in “6206”, “0 6” corresponds to the bore diameter, therefore, “0 6” translates into a bearing bore diameter of 6*5=30mm.
If there is no fourth digit in the bearing number, the third digit represents the bore diameter.
For example, for a bearing size “234”, the number “4” (equivalent to 4 mm) indicates the bore diameter.
*00 | 10 mm |
*01 | 12 mm |
*02 | 15 mm |
*03 | 17 mm |
*04 | 20 mm (4 x 5 mm) |
*05 | 25 mm (5 x 5 mm) |
*06 | 30 mm (6 x 5 mm) |
above | above => multiplication of 5mm |
* In case there is no fourth digit, then the 3rd digit indicates the bore size in mm. For example: in case of bearing 636, the bore size of the bearing will be 6mm | |
Suffix
Suffixes indicate different designs or variations that deviate from the original or current basic design. For example, shielded bearings and sealed bearings have different suffixes. For “6 2 0 6 LLB”, “LLB” stands for bearings with non-contact rubber seals.
Suffix | Description |
RS | with rubber seal on one side, one side open |
2 RS | with rubber seal on both sides |
Z | with a metal seal on one side, one side open |
2 Z / ZZ | with a metal seal on both sides |
V | One side Non-Contact Seal |
VV | Both Sides Non-Contact Seal |
DDU | Both sides Contact Seals |
Suffixes- Clearance | ||||||
Meaning | Normal radial internal clearance (RIC) | Radial internal clearance smaller than C2 | Radial internal clearance smaller than normal radial internal clearance greater than normal | Radial internal clearance greater than normal | Radial internal clearance greater than C3 | Radial internal clearance greater than C4 |
Code | C0/CN | C1 | C2 | C3 | C4 | C5 |
In addition to seals or guards, there are other suffixes such as cage design, materials, heat treatment, accuracy, clearance, preload, quiet operation, stability, lubrication, and other special specifications.
Examples of bearing numbers
Tips for interpreting the meaning of bearing numbers
Take advantage of resources: Use manufacturer’s guides and online tools for bearing identification.
Understand structure: Understand the meaning of prefixes, base names, and suffixes.
Avoid Assumptions: Verify bearing numbers from each manufacturer – do not assume they are the same.
Check for errors: Watch out for spelling errors as they may change the bearing specification.
Ask when unsure: If you are unsure about the bearing number, please consult a bearing expert and Aubearing will answer your question immediately.
Conclusion
Identifying bearings by number requires understanding the bearing terminology and numbering system used by the manufacturer. Each bearing number encodes specific information about the bearing type, size and design. Typically, this number includes a series code indicating the bearing type, a size series code indicating the bearing’s dimensional characteristics, and additional suffixes indicating specific design features such as seals, guards, or internal clearance. It is important to know whether the manufacturer follows the ABMA bearing code standards or uses a different standard. All manufacturers provide code keys on their websites or catalogs to help users interpret or specify the bearings required for their application. Regardless of which numbering system is used, each number and letter used in a bearing code has a specific meaning and helps identify the type and specification of the bearing. Many manufacturers or distributors offer bearing number crossovers to facilitate interchange of bearings from one manufacturer to another. Due to the lack of interchange guidance for other bearing manufacturers, most suppliers will provide information for switching between their numbers and the ABMA standard.