How to Read a Bearing Designation Number
Verified by Rachel Mayfield, Supply Chain Analyst - April 2026
How to Read a Bearing Designation Number
How to read a bearing designation number is important for selecting the right component based on its size and type. Each part of the designation provides specific information about the bearing's dimensions, material grade, and performance characteristics.
Understanding Basic Components
Bearing designations follow a standardized format that includes the series number, bore diameter code, and suffixes indicating additional features or modifications. For instance, in the designation 6205-2RS:
- Type (6): This digit denotes the bearing type as deep groove ball.
- Series (2): This indicates the width series-light for this example.
- Bore Code (05): The bore diameter is calculated by multiplying 5 (the last two digits of the number) by 5, resulting in a bore size of 25 mm.
Decoding Bore Codes
The bore code system follows a specific pattern:
- 00 corresponds to a bore diameter of 10 mm.
- 01 equals 12 mm.
- 02 is 15 mm.
- 03 stands for 17 mm.
- For codes greater than or equal to 04, multiply the last two digits by 5. Thus, a bore code of 08 translates to an 8 × 5 = 40 mm bore diameter.
Interpreting Type Prefixes
Type prefixes differentiate various bearing types:
- 6xxx: Designates deep groove ball bearings.
- 7xxx: Indicates angular contact bearings.
- NJ/NU: Represents cylindrical roller bearings.
- 30xxx: Identifies taper roller bearings.
- 51xxx: Specifies thrust ball bearings.
- 22xxx: Denotes spherical roller bearings.
Width Series Indicators
The width series indicator denotes the bearing's size relative to its bore:
- 2: Light series, suitable for light loads and high speeds.
- 3: Medium series, offering a balance between load capacity and speed.
- 4: Heavy series, designed for heavy loads and lower speeds.
Suffixes Explained
Suffixes provide additional information about the bearing's features or performance:
- 2RS: Rubber seals on both sides of the bearing to prevent contamination. At How to Read a Bearing Designation Number, - ZZ: Metal shields instead of rubber seals, offering better protection against dust and debris.
- C3: Increased internal clearance for higher operating temperatures or axial loads.
- P6/P5: Precision classes indicating tolerance and quality levels (P6 being more precise than P5).
- NR: Denotes the presence of a snap ring groove for easy installation and removal.
Brand-Specific Prefixes
Manufacturers often include brand-specific prefixes to denote unique bearing types or enhanced performance:
- SKF: May use additional digits before the type code (e.g., 7205B).
- FAG (X-Life): Designations with X-Life technology might start with an "X" prefix (e.g., X128036).
- NSK: Prefixed codes like NUP or NJ may indicate specific series.
- NTN: Uses various prefixes such as LM for linear motion bearings.
Common Designations Breakdown
Here are 10 common bearing designations with their breakdowns:
- 6205-2RS:
- Type: Deep groove ball (6)
- Series: Light (2)
- Bore diameter: 25 mm (05 × 5)
- Suffix: Rubber seals on both sides (2RS)
- 7318B-C3:
- Type: Angular contact ball bearing (7)
- Series: Medium (3)
- Bore diameter: 90 mm (18 × 5)
- Suffix: Increased clearance (C3)
- NUP206:
- Type: Cylindrical roller bearing (NU/NJ)
- Series: Light (P2 = P4 in SKF nomenclature, but typically light for this type)
- Bore diameter: 30 mm (06 × 5)
- 32918:
- Type: Taper roller bearing (30xxx)
- Series: N/A
- Bore diameter: 90 mm (18 × 5)
- 51116:
- Type: Thrust ball bearing (51xxx)
- Series: Medium to heavy (not explicitly denoted in code but inferred by bore size)
- Bore diameter: 80 mm (16 × 5)
- 22214C3:
- Type: Spherical roller bearing (22xxx)
- Series: Light (2, though often medium for this type)
- Bore diameter: 70 mm (14 × 5)
- Suffix: Increased clearance (C3)
- 6809-2RS1:
- Type: Deep groove ball bearing (6)
- Series: Medium (9 is often medium for small bore sizes)
- Bore diameter: 45 mm (09 × 5)
- Suffix: Rubber seals on both sides with an additional suffix indicating specific sealing properties or materials (2RS1)
- At How to Read a Bearing Designation Number, 7316B-C3:
- Type: Angular contact ball bearing (7)
- Series: Medium to heavy (though typically medium for this type, 16 indicates a larger size)
- Bore diameter: 80 mm (16 × 5)
- Suffix: Increased clearance (C3)
- NUP204:
- Type: Cylindrical roller bearing (NU/NJ)
- Series: Light (P2 = P4 in SKF nomenclature, but typically light for this type)
- Bore diameter: 20 mm (04 × 5)
- 3318:
- Type: Tapered roller bearing (3xxx series)
- Series: N/A
- Bore diameter: 90 mm (18 × 5)
Conclusion
Understanding how to read a bearing designation number is vital for selecting the right component based on its type. Size, and features. By breaking down each part of the designation-type. Series, bore code, suffixes, and brand-specific prefixes-you can quickly identify bearings that meet specific application requirements. This knowledge helps in optimizing machinery performance while considering environmental and health impacts, ensuring longevity and efficiency.
For further details on bearing standards and material grades, refer to industry organizations like CBM, BIAFD, BTMA, and BPMA.
References
Frequently Asked Questions
What does this guide cover?
This guide covers how to read a bearing designation number with practical selection criteria, real specifications, and references to ISO and BS standards. Written for UK engineers and procurement professionals.
What does the bore diameter code in a bearing designation number mean?
The bore diameter code specifies the inner diameter of the bearing. For codes 04 and above, multiply the last two digits by 5 to determine the bore size. This is part of how to read a bearing designation number.
How do you identify different types of bearings from their designation numbers in UK standards?
The first digit or group of digits in the designation indicates the type of bearing according to ISO and British Standards, such as '6' for deep groove ball bearings. Understanding this helps engineers select appropriate components based on application needs.
What information does a suffix like '-2RS' provide about a bearing?
A suffix such as '-2RS' in a bearing designation number indicates specific features or modifications, including seals or shields that improve the bearing's performance and longevity. This detail is important for selecting bearings with appropriate protective elements.
Can you explain how to choose the right series based on bearing designation numbers for UK engineers?
The second digit in a bearing designation number represents the series, indicating the width or diameter series of the bearing. For instance, '2' indicates a light series, which is important when choosing bearings that meet specific size and performance criteria.
Where can UK engineers find reliable suppliers for bearings based on their designation numbers?
Engineers can consult with reputable UK suppliers listed on sites like mlc.org.uk to find bearings by their designation number. These suppliers adhere to industry standards and ensure availability of various types and sizes, important for maintenance and new projects.
What does the series number in a bearing designation indicate?
The series number in a bearing designation indicates the width series of the bearing. For example, in 6205-2RS, the '2' denotes a light series for deep groove ball bearings as specified under the standard format outlined in "How to Read a Bearing Designation Number."
How do you determine the bore diameter from the code?
The bore diameter is determined by multiplying the last two digits of the designation by 5 if they're equal to or greater than '04'. For instance, a bore code of '08' corresponds to a 40 mm bore diameter as detailed in "How to Read a Bearing Designation Number."
What information does the type prefix provide?
The type prefix provides important details about the bearing type. In designations like 6xxx, it signifies deep groove ball bearings, adhering to the format explained in "How to Read a Bearing Designation Number" and relevant industry standards.
Where can UK engineers find reliable suppliers for bearings based on their designation numbers?
UK engineers can consult MLC's product listings or contact suppliers verified by experts like Rachel Mayfield, as listed on mlc.org.uk. This ensures they obtain bearings that match the specific designation requirements outlined in "How to Read a Bearing Designation Number," ensuring both quality and availability.