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ادامه مطلبThe 6208 bearing is a single-row deep groove ball bearing with a 40 mm bore diameter, 80 mm outer diameter, and 18 mm width, making it one of the most versatile and widely used bearings across automotive, industrial, and agricultural machinery sectors. Its standardized dimensions, high radial load capacity, and moderate axial load tolerance have made it a go-to component for engineers and maintenance professionals worldwide.
The 6208 bearing follows the ISO 15 standard for deep groove ball bearings, with precise dimensional tolerances that ensure interchangeability across manufacturers. Below are the core specifications that define this bearing's mechanical identity.
| Parameter | Value | Unit |
| Bore Diameter (d) | 40 | mm |
| Outer Diameter (D) | 80 | mm |
| Width (B) | 18 | mm |
| Dynamic Load Rating (C) | 29,000 – 32,500 | N |
| Static Load Rating (C₀) | 17,800 – 19,000 | N |
| Reference Speed | 9,000 | rpm |
| Limiting Speed | 6,700 | rpm |
| Weight (approx.) | 0.28 | kg |
The designation "6208" follows a globally standardized numbering system that encodes the bearing's geometry and series type. Understanding this code helps engineers quickly identify compatible replacements:
Suffix codes are frequently appended to indicate sealing, clearance, or material variants. For example, 6208-2RS features rubber seals on both sides, while 6208-ZZ uses metal shields.
Choosing the correct 6208 bearing variant is critical because sealing type, clearance class, and material directly affect service life and suitability for a given application. The following comparison covers the most common variants:
| Variant | Sealing | Relubrication | Best For |
| 6208 (Open) | None | Yes | Clean, dry, high-speed environments |
| 6208-ZZ | Metal shield (both sides) | No | Dusty environments, electric motors |
| 6208-2RS | Rubber seal (both sides) | No | Wet/moist environments, food processing |
| 6208-NR | Open + snap ring groove | Yes | Axial positioning in housings |
| 6208/C3 | Open or sealed | Varies | High-temperature, thermal expansion applications |
Internal clearance determines how much play exists between the rolling elements and raceways, directly affecting noise, heat generation, and load distribution.
The 6208 bearing is found in virtually every major industrial sector due to its balanced combination of load capacity, speed capability, and dimensional standardization. Its 40 mm bore fits a wide range of shaft sizes used in mid-range machinery.
In automotive applications, the 6208 bearing is extensively used in alternators, power steering pumps, and transmission assemblies. Its ability to handle combined radial and axial loads makes it ideal for drivetrain components where both directions of force are present during vehicle operation.
The 6208-ZZ and 6208-2RS variants are the standard choice for electric motors in the 2–15 kW power range. The bearing's low friction characteristics help maintain motor efficiency, while the sealed variants prevent contamination of the motor windings from grease migration.
Tractors, harvesters, and irrigation pumps heavily rely on the 6208 bearing for gearbox and PTO shaft support. In agricultural settings, the C3 clearance version combined with a rubber seal (6208-2RS/C3) is preferred because it tolerates both temperature variation in the field and contamination from soil, dust, and moisture.
Centrifugal pumps and HVAC fan assemblies regularly specify the 6208 bearing as the primary shaft support element. Its high reference speed of 9,000 rpm suits fan and blower applications, and its compact cross-section helps minimize overall equipment envelope.
In conveyor systems, the 6208 bearing supports idler rollers and drive shafts where continuous operation and long service intervals are essential. Maintenance teams often select the pre-greased sealed variant to reduce lubrication schedules in hard-to-reach locations.
Comparing the 6208 with neighboring sizes in the 02-series helps engineers select the optimal bearing when load or space requirements are near the boundary.
| Model | Bore (mm) | OD (mm) | Width (mm) | Dynamic Load (N) | Max Speed (rpm) |
| 6206 | 30 | 62 | 16 | 19,500 | 13,000 |
| 6207 | 35 | 72 | 17 | 25,700 | 10,000 |
| 6208 |
40 | 80 | 18 | 29,000–32,500 | 9,000 |
| 6209 | 45 | 85 | 19 | 33,200 | 8,500 |
| 6210 | 50 | 90 | 20 | 35,100 | 8,000 |
Highlighted row: 6208 bearing (subject of this article)
Proper installation is the single most important factor in achieving the rated service life of a 6208 bearing — improper fitting causes more premature failures than any other factor.
Correct lubrication type and quantity is essential for achieving the full rated life of a 6208 bearing; both under-lubrication and over-lubrication are harmful.
| Lubricant Type | Operating Temperature | Speed Suitability | Notes |
| Lithium Grease NLGI 2 | -30°C to +120°C | Up to 9,000 rpm | Most common choice; good water resistance |
| Lithium Complex Grease NLGI 3 | -20°C to +180°C | Up to 7,000 rpm | High-temp applications, motors |
| Mineral Oil ISO VG 68 | 0°C to +80°C | High-speed (oil bath/mist) | Oil lubrication for gearboxes |
| Synthetic PAO Grease | -50°C to +200°C | Wide range | Extreme temperature environments |
Early detection of 6208 bearing deterioration prevents unexpected downtime and collateral equipment damage. The following signs indicate that a bearing inspection or replacement is needed:
| Failure Mode | Probable Cause | Prevention |
| Spalling / Fatigue | Overload, incorrect clearance | Check load ratings, use C3 if needed |
| Corrosion | Water ingress, poor sealing | Use 6208-2RS; check seals regularly |
| Wear / Abrasion | Contaminated lubricant | Use sealed variants; maintain clean installation |
| Electrical Erosion | Stray currents through bearing | Use insulated housing or ceramic balls variant |
| False Brinelling | Vibration during standstill | Preload bearing slightly; use anti-fretting grease |
Q1: What is the difference between a 6208 and a 6208-2RS bearing?
The 6208 is an open bearing requiring periodic relubrication, while the 6208-2RS has rubber contact seals on both sides and is pre-filled with grease for maintenance-free operation. The 2RS variant offers better protection against moisture and contamination, making it preferred in sealed or hard-to-service locations. The trade-off is slightly higher friction and a lower limiting speed (~7,000 rpm vs. 9,000 rpm for open).
Q2: Can a 6208 bearing handle both radial and axial loads?
Yes — the deep groove ball bearing design of the 6208 allows it to handle radial loads primarily, plus moderate axial (thrust) loads in both directions. The axial load capacity is approximately 25–30% of the static radial load rating. For predominantly axial loads, an angular contact bearing would be more suitable.
Q3: How long does a 6208 bearing last?
Under ideal conditions, a 6208 bearing has a calculated L10 basic rating life (the life at which 10% of bearings will have failed) that can exceed 20,000 to 50,000 operating hours depending on load and speed. Real-world service life is significantly affected by mounting quality, lubrication maintenance, contamination control, and alignment. Typical industrial applications see 3–10 years of service before replacement.
Q4: What does the "C3" suffix mean on a 6208/C3 bearing?
C3 indicates a greater-than-normal internal radial clearance, which is needed when the bearing will experience significant temperature rise or is installed with an interference fit. Without sufficient clearance, thermal expansion can eliminate the internal play entirely, causing preload, overheating, and premature fatigue failure. C3 is the most commonly specified non-standard clearance for motor and pump applications.
Q5: Is the 6208 bearing interchangeable across different manufacturers?
Yes — because the 6208 bearing follows ISO 15 dimensional standards, bearings of the same designation from different manufacturers are dimensionally interchangeable. However, quality levels, material grades, internal geometry, and load ratings may differ between manufacturers. Always verify load ratings and operating conditions when substituting, especially in critical applications.
Q6: What is the correct grease fill amount for an open 6208 bearing?
The recommended grease fill for an open 6208 bearing is 30–50% of the bearing's internal free space, which equates to approximately 4–7 grams of grease. Over-greasing is a common maintenance error that causes churning, heat buildup, and seal damage. Under-greasing leads to metal-to-metal contact and accelerated wear.
The 6208 bearing remains one of the most cost-effective, versatile, and globally available bearings for 40 mm shaft applications across virtually every industry. Its standardized dimensions guarantee interchangeability, its deep groove geometry provides reliable combined load handling, and the wide range of variants — from open to sealed, from standard to C3 clearance — ensures that a suitable specification exists for nearly every operating environment.
When selecting a 6208 bearing, the key decisions are: sealing requirement (open vs. ZZ vs. 2RS), clearance class (CN vs. C3), material (standard steel vs. stainless vs. ceramic hybrid), and lubrication type. For the vast majority of industrial applications — electric motors, pumps, conveyor drives, and agricultural equipment — the 6208-2RS/C3 with lithium complex grease represents the optimal balance of performance, protection, and maintenance simplicity.
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غرب منطقه صنعتی Zhangting، Yuyao، شهر نینگبو، استان ژجیانگ، 315411، چین
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