This article solves 5 key problems buyers face when sourcing AST 6808-2RS thin section sealed bearings, ensuring you get the right component for your application and avoid costly mistakes. We’ll cover essential quality checks, crucial application considerations, and how to navigate the complex world of bearing suppliers.
The AST 6808-2RS thin section sealed bearing is a specific type of radial ball bearing. Its defining characteristic is its “thin section” design, meaning the ratio of the bearing’s bore diameter to its outside diameter is relatively small. This allows for space and weight savings in applications where those are critical factors. The “2RS” designation indicates that it is sealed on both sides with rubber seals (R seals) to retain lubricant and prevent the ingress of contaminants like dirt and moisture.
These bearings find applications in a variety of industries, notably:
- Robotics: Lightweight robotic arms and joints.
- Aerospace: Aircraft instruments and control systems.
- Medical Equipment: Surgical tools, imaging equipment.
- Industrial Automation: Precision machinery, indexing tables.
- Semiconductor Manufacturing: Wafer handling equipment.
The material used in the bearing’s rings and balls significantly impacts its performance and lifespan. Typically, these bearings are made from SAE 52100 chrome steel (AISI 52100) for its high hardness, wear resistance, and fatigue strength (https://en.wikipedia.org/wiki/SAE_52100_steel). However, for corrosive environments, stainless steel (e.g., 440C) might be a better choice, but with a potential trade-off in load capacity.
Always request material certifications from your supplier to confirm the actual composition.
Beyond the material itself, hardness is critical. Rockwell hardness (HRC) testing is commonly used. For 52100 steel, the bearing rings should ideally be hardened to HRC 58-62. Lower hardness can result in premature wear and failure.
Don’t assume the bearing meets spec; verify the hardness rating before installation.
The “2RS” designation means sealed, but not all seals are created equal. Inspect the seals for proper fit, material quality (NBR is a common material), and flexibility. A damaged or poorly fitted seal will compromise the bearing’s protection against contamination.
Beyond the seals themselves, lubrication compatibility is vital. The factory-installed grease must be compatible with your application’s operating temperature, speed, and load.
Request the grease specifications (type, viscosity, operating temperature range) from your supplier.
Using an incompatible grease can lead to premature bearing failure due to lubrication breakdown or hardening.
First-hand Insight: I once worked on a robotic arm project where we didn’t pay close attention to the grease compatibility. We ended up with hardened grease inside the bearings after just a few weeks of operation, leading to jerky movements and ultimately requiring a complete bearing replacement. It was a costly lesson learned about the importance of lubrication compatibility.
Thin section bearings, by their nature, demand precise dimensions. Even minor variations can lead to fitment issues, preload problems, and ultimately, reduced bearing life.
Verify the following dimensions with precision measuring tools (calipers, micrometers):
- Bore Diameter: Ensure it matches your shaft diameter.
- Outside Diameter: Ensure it fits correctly into the housing.
- Width: Check for proper alignment and spacing.
Runout is another crucial parameter. It refers to the amount of wobble or eccentricity in the bearing’s rotation. Excessive runout can cause vibration, noise, and premature wear.
Check for both radial and axial runout using a dial indicator, ensuring they are within the manufacturer’s specified tolerances.
A common misconception is that a “slightly loose” fit is acceptable. However, in high-precision applications, any looseness can lead to fretting corrosion and accelerated wear.
Bearings have static and dynamic load capacities. The static load capacity is the maximum load the bearing can withstand without permanent deformation when stationary. The dynamic load capacity is the load the bearing can endure for a specific lifespan (usually defined in millions of revolutions) at a given speed.
Ensure that the bearing’s load capacities (both static and dynamic) exceed the actual loads in your application with a safety factor.
Speed rating is also critical. Exceeding the bearing’s speed limit can generate excessive heat, leading to lubricant breakdown and bearing failure.
Consult the bearing manufacturer’s datasheet to confirm load capacities and speed ratings for your specific operating conditions (temperature, lubrication type).
Counterfeit bearings are a serious problem. These bearings often use inferior materials, have poor manufacturing quality, and fail prematurely, leading to costly downtime and potential safety hazards.
Choose reputable suppliers with a proven track record and strong quality control processes.
Request traceability information, including the bearing’s manufacturing date, batch number, and origin.
Be wary of suppliers offering bearings at significantly lower prices than the market average – this could be a red flag for counterfeit products.
Table: Key Considerations for Choosing AST 6808-2RS Thin Section Sealed Bearings
| Feature | Consideration | Importance |
|---|---|---|
| Material | Confirm material type (e.g., 52100 steel, stainless steel) and hardness (HRC). Request certifications. | High |
| Seals | Inspect seal quality (material, fit). Ensure compatibility with your operating environment. | High |
| Lubrication | Verify grease type, viscosity, and operating temperature range. Ensure compatibility with your application. | High |
| Dimensions | Precisely measure bore diameter, outside diameter, and width. | High |
| Runout | Check radial and axial runout using a dial indicator. Compare to manufacturer specifications. | High |
| Load Capacity | Ensure static and dynamic load capacities exceed application loads with a safety factor. | High |
| Speed Rating | Confirm the speed rating is adequate for your application’s operating speed. | High |
| Supplier | Choose reputable suppliers with traceability information. Be wary of unusually low prices. | High |
| Operating Temp. | Consider high temperature bearing grease for applications exceeding standard temp ranges, to prevent premature degradation | Medium |
Beyond the technical specifications, consider the overall lifecycle cost of the bearing. A slightly more expensive bearing with a longer lifespan can often be more cost-effective in the long run.
Another often overlooked aspect is noise and vibration. In some applications, such as medical equipment, low noise and vibration are critical. Consider bearings with tighter tolerances and optimized internal geometry for reduced noise.
My personal experience shows that building a relationship with a knowledgeable bearing supplier can be invaluable. They can provide expert advice on bearing selection, installation, and maintenance, helping you optimize your application’s performance and reliability. Don’t just treat them as a vendor; consider them a technical partner.
By carefully considering these five checks and adopting a proactive approach to bearing selection and sourcing, you can minimize the risk of premature bearing failure and maximize the performance and reliability of your equipment.
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