1. What Are Bearing Codes?
Bearing codes—also called bearing numbers or bearing designation systems—are standardized identifiers used by manufacturers to describe the bearing’s type, dimensions, and technical specifications.
Most global brands (SKF, NTN, NSK, Timken, FAG, Koyo) follow the ISO bearing designation standard, with slight variations in suffixes.
A typical bearing code looks like:
- 6204 ZZ
- 32008 X/Q
- 6310 C3
- 22218 EK
2. Understanding the Core Bearing Number (Basic Designation)
2.1 Bearing Type (Prefix)
Some bearings include a type prefix:
| Prefix | Meaning |
|---|---|
| N | Cylindrical roller bearing |
| NU | Cylindrical roller bearing, single row |
| 3 | Tapered roller bearing (common in TRB series) |
| QJ | Four-point contact ball bearing |
Not all codes include prefixes—deep groove ball bearings usually start directly with the series number (e.g., 6200).
2.2 Bearing Series (First Digit of Main Number)
This indicates the load capacity / robustness of the bearing:
| First Digit | Series | Meaning |
|---|---|---|
| 6 | Deep groove ball bearing | |
| 7 | Angular contact ball bearing | |
| 2 | Spherical roller bearing | |
| 3 | Tapered roller bearing |
Example:
6204 → “6” means deep groove ball bearing.
2.3 Diameter Series (Second Digit)
Defines the cross-section size of the bearing:
| Digit | Series | Meaning |
|---|---|---|
| 0 | Extra light | |
| 1 | Light | |
| 2 | Medium | |
| 3 | Heavy |
Example:
6204 → “2” = medium series.
2.4 Bore Size (Last Two Digits)
Bore = inner diameter.
| Bore Code | Actual Bore Size |
|---|---|
| 00 | 10 mm |
| 01 | 12 mm |
| 02 | 15 mm |
| 03 | 17 mm |
| 04+ | Multiply by 5 (e.g., 05 → 25 mm, 10 → 50 mm) |
Example:
6204 → “04” = 20 mm bore.
3. Understanding Bearing Suffixes & Codes
Suffixes are crucial—they describe clearance, seal type, cage material, precision, and internal design.
3.1 Clearance Codes
| Suffix | Meaning |
|---|---|
| C2 | Less than normal clearance |
| C3 | Greater than normal clearance |
| C4 | Extra clearance |
| C5 | Very large clearance |
Example:
6310 C3 → increased internal clearance for high-speed or high-temperature applications.
3.2 Seal/Shield Codes
| Suffix | Meaning |
|---|---|
| Z | One metal shield |
| ZZ | Two metal shields |
| RS | One rubber seal |
| 2RS | Two rubber seals |
| N | Snap ring groove |
| NR | Snap ring + groove |
Example:
6204 2RS → double rubber-sealed bearing.
3.3 Cage Material Codes
| Suffix | Cage Material |
|---|---|
| J | Steel cage |
| TV / TN / TNG | Polyamide / nylon cage |
| M | Brass cage (machined) |
| MA / MB | Brass cage variations |
3.4 Precision Grades
| Code | Standard | Application |
|---|---|---|
| P0 | Normal | General use |
| P6 | Higher precision | Motors, gearboxes |
| P5 | High precision | Machine tools |
| P4 | Very high precision | Spindles |
| P2 | Ultra precision | High-end CNC systems |
3.5 Internal Design / Manufacturer Codes
Different brands use custom suffixes:
| Code | Meaning |
|---|---|
| E | Reinforced internal design (higher load) |
| K | Tapered bore |
| X | Special internal design (common in tapered bearings) |
| Q | Optimized geometry |
Example:
22218 EK → spherical roller bearing, 90 mm bore, tapered bore + reinforced design.
4. Bearing Code Examples (Explained)
Example 1: 6205 ZZ C3
- 6 → Deep groove ball bearing
- 2 → Medium series
- 05 → 25 mm bore
- ZZ → Double metal shields
- C3 → Increased clearance
Best for: electric motors, fans, pumps.
Example 2: 32008 X/Q
- 3 → Tapered roller bearing
- 2008 → Series + bore combination
- X → Special inner geometry
- /Q → Special load distribution (SKF code)
Used in: automotive wheel hubs, industrial gearboxes.
Example 3: 22218 EK
- 2 → Spherical roller bearing
- 2218 → Size series
- K → Tapered bore
- E → Reinforced load capacity
Used in: heavy machinery, mining conveyors.
5. How to Identify if Codes Follow ISO or Manufacturer Standards
ISO-Based Codes
Most ball and roller bearing codes follow ISO 15 / ISO 355.
Manufacturer-Specific Suffixes
Brands often add proprietary codes (e.g., SKF “TN9”, NSK “DU”, NTN “ZZC3”), but the core number usually remains ISO-compatible.
6. Why Learning Bearing Codes Matters
Correctly reading bearing codes helps you:
- Avoid selecting the wrong clearance or seal type
- Match OEM numbers when sourcing replacements
- Evaluate brands with compatible specifications
- Improve engineering design accuracy
- Reduce equipment downtime
7. Quick Reference Chart (Cheat Sheet)
| Element | Meaning |
|---|---|
| Basic designation | Bearing type + series + bore |
| Suffix | Clearance, cage, seal, precision |
| Prefix | Special bearing design |
| Bore code | Final two digits |
| C3/C4 | Clearance levels |
| ZZ/2RS | Shield/seal options |
8. Final Tips for Engineers & Buyers
- Always check bearing clearance for motor applications (C3 often required).
- For dusty environments, choose 2RS seals over ZZ shields.
- Verify cage type for high-speed applications (nylon or brass recommended).
- For high-load applications, look for E / E1 / EM reinforced designs.
- Don’t mix precision classes across different machine axes.