Product Overview
This page provides a detailed engineering and procurement reference for the 6208, intended for buyers verifying exact bearing specifications and functional interchangeability before ordering.
As one of the most essential sizes in the standard metric series, the 6208 Single Row Deep Groove Ball Bearing is specifically developed by ZQM Bearings to sustain continuous operation in high-speed, medium-load environments. Primarily utilized in heavy-duty electric motors, centrifugal pumps, and industrial gearboxes, this model is the engineering choice for procurement professionals seeking a reliable replacement that meets rigorous ISO standards for vibration reduction and fatigue resistance. Its deep raceway tracks and optimized ball conformity enable the 6208 to manage substantial radial loads while simultaneously accommodating axial forces in both directions, making it a critical component for machinery requiring high precision and predictable service life.
Design & Engineering Advantages
The 6208 is synthesized from premium vacuum-degassed GCr15 high-carbon chromium bearing steel. This material selection is a calculated engineering decision targeting the mitigation of fatigue spalling by controlling oxygen content to sub-5 ppm levels, effectively reducing non-metallic inclusions. In high-speed ball bearings, steel purity directly correlates to the fatigue limit and vibration damping. Our controlled manufacturing processes ensure that the 6208 maintains superior Hertzian contact stress distribution across the rolling elements, thereby preventing early-stage crack initiation under cyclic stress.
The internal geometry is optimized for low friction torque, which is essential for minimizing heat generation at the limiting speed of 11,000 r/min. The 80 mm outside diameter (D) and 40 mm bore (d) create a robust cross-section that maximizes radial load efficiency without compromising axial stiffness. Unlike more complex roller designs, the 6208 utilizes a high-precision pressed steel cage, providing exceptional thermal stability and self-guiding properties for the rolling elements. This allows for stable internal clearance optimization even during the thermal expansion phases of heavy industrial service cycles. The deep raceways are precision-honed to P6 level (ISO class 6) as standard, ensuring that the boundary lubrication layer is consistently maintained and preventing the risk of thermal seizure in boundary lubrication conditions.
Key Features
- High-purity vacuum-degassed GCr15 steel for maximum fatigue resistance.
- Deep groove geometry for versatile radial and combined axial load paths.
- Low-friction pressed steel cage for high-speed operation and thermal management.
- Precision P6 (ISO Class 6) manufacturing for low noise and vibration.
- Universal interchangeability with global ISO/DIN 6208 series standards.
Boundary Dimensions
| Designation | 6208 |
| Bore diameter (d) | 40 mm |
| Outside diameter (D) | 80 mm |
| Width (B) | 18 mm |
Procurement Selection
From a TCO (Total Cost of Ownership) perspective, the procurement of the 6208 represents a high-reliability decision for standardizing industrial motor and drive components. Engineering teams should prioritize this model for its balanced performance envelope, which excels in applications requiring high rotational accuracy and minimal frictional energy loss. The functional interchangeability of the 6208 ensures that procurement verification is straightforward, matching exactly the dynamic load rating of 32.5 kN required for legacy and modern equipment replacements. For environments involving high temperature or significant shaft interference, selecting the C3 clearance variant is recommended to prevent internal clearance loss. ZQM ensures dimensional consistency across every batch, reducing the overhead of repeated procurement audits and ensuring a predictable replacement schedule.
Cross-reference & Replacement
| ZQM Model | Reference Brand | Reference Model | Equivalence Basis |
|---|---|---|---|
| 6208 | SKF | 6208 | ISO Dimensional conformity |
| 6208 | FAG | 6208-C | Installation interchangeability |
| 6208 | NSK | 6208 | Internal geometry compatibility |
The 6208 is specifically engineered for replacement evaluation across a vast range of industrial hardware. ZQM Bearings provides these references to support procurement professionals. Technical audits should always verify the shaft abutment (da min=47 mm) and housing abutment (Da max=73 mm) dimensions to ensure proper structural fit during installation, preventing localized stress peaks and vibration.
Typical Industrial Applications
- Medium to Large Electric Motors
- Industrial Centrifugal Pumps and Compressors
- Automotive Transmission Gearboxes
- Agricultural Machinery Drive Shafts
- Conveyor Pulleys and Material Handling Equipment
Service Life & Reliability
The reliability of the 6208 is grounded in advanced L10 Life Calculation Logic, where the relationship between raceway honing and material purity is maximized. By reducing friction torque through precision finishing, the bearing maintains its heat treatment stability, preventing dimensional drift that could lead to early clearance loss. High-speed industrial environments demand that the bearing resists subsurface-initiated fatigue; ZQM achieves this by controlling inclusion levels, ensuring that the 6208 achieves its full theoretical fatigue life. The 19 kN static load rating (C0) provides a robust safety factor against permanent deformation (brinelling) during stationary vibration or impact loads, which is critical for equipment that undergoes frequent start-stop cycles.
Installation & Lubrication Notes
Success in high-speed applications depends heavily on precise misalignment compensation. Deep groove ball bearings like the 6208 have limited tolerance for misalignment; exceeding 0.001 radians will lead to increased noise and early raceway failure. Relubrication intervals should follow the speed ratings—Reference speed 18,000 r/min and Limiting speed 11,000 r/min—to avoid boundary lubrication failure. Incorrect grease volume is a primary cause of thermal seizure; ensure the fill level matches the specific industrial service cycle requirements. Proper mounting using cold-mounting tools or induction heaters is essential to protect the precision-honed internal raceways from mounting damage.
Frequently Asked Questions
How does material purity influence the fatigue resistance of 6208 bearings?
Material purity is the primary determinant of the L10 fatigue life in the 6208. By using vacuum-degassed GCr15 steel, ZQM minimizes non-metallic inclusions that otherwise act as stress concentration points under the contact subsurface. If inclusions are present, the constant Hertzian contact stress will trigger subsurface cracks, leading to premature fatigue spalling. High purity ensures that the 6208 maintains its dimensional stability and load-carrying capacity over millions of stress cycles in industrial gearboxes and motors.
What is the difference between CN and C3 clearance for a 6208 bearing?
CN (Normal) clearance is the standard internal gap for most general-purpose applications. C3 clearance provides a larger internal gap, which is necessary when the 6208 operates in high-temperature environments or when there is a heavy interference fit on the shaft. Choosing C3 ensures that internal clearance optimization is maintained even after thermal expansion, preventing the bearing from running too hot and suffering thermal seizure, which is vital for long-term reliability.
Can a 6208 bearing handle axial loads effectively?
Yes, the 6208 deep groove ball bearing is designed to manage combined radial and axial loads. The deep raceway grooves allow the balls to track securely even under axial pressure. However, the axial load capacity is typically limited to a percentage of the static load rating (C0). For applications with pure axial forces or high axial-to-radial ratios, angular contact bearings might be required, but for standard pump and motor shafts, the 6208 is the engineering standard.
Why is low vibration (Z2/Z3) important for the 6208 in industrial motors?
In industrial motors, bearing vibration is a critical indicator of manufacturing precision and lubrication reliability. Low vibration levels (Z2/Z3) prevent the bearing from generating resonant noise that could damage motor windings or lead to premature structural failure of the housing. ZQM 6208 bearings undergo 100% vibration testing to ensure the raceway honing meets the strict requirements for low friction torque and quiet operation in high-speed motor environments.
What are the critical installation abutment dimensions for the 6208?
For a 6208 installation, the shaft abutment (da min) should be 47 mm, and the housing abutment (Da max) should not exceed 73 mm. If these dimensions are not respected, the bearing’s load path will be compromised, leading to vibration stress or axial drift. The fillet radius (ra max=1 mm) must be strictly controlled to ensure the 6208 sits flush against the shoulder, maintaining its precise axial positioning and load distribution for long-term service life.
How do I select the right seal for a 6208 bearing in contaminated environments?
In environments with heavy contamination, choosing between shielded (ZZ) or sealed (2RS) variants is critical. While the 6208 open variant offers the lowest friction, the 2RS variant provides superior protection against dust and moisture ingress, significantly extending the relubrication cycle. For high-speed applications with moderate contamination, non-contact shields might be preferred to balance protection with low heat generation. ZQM engineers can assist in selecting the optimal sealing strategy based on your specific TCO requirements.
Related Bearing Models
- 6207
- 6209
- 6008
- 6308
- 16208
Technical Support & Global Inquiry
ZQM Bearings supports long-term supply programs for international OEMs and distributors, emphasizing batch-to-batch dimensional consistency and controlled manufacturing processes. Our engineering team focuses on standardized quality control across repeated production batches to ensure consistent fit and performance for overseas shipments.
Standardized export packaging and anti-rust surface treatment are provided for all overseas shipments to maintain the dimensional integrity of your order. ZQM engineers provide 24/7 technical selection support to ensure the selected bearing solution matches your specific industrial application needs. Request a customized quote for bulk orders or OEM-specific bearing requirements to support your high-performance projects.
