Household metal storage cabinets Dongguan Shangen Precision Metal Plate Co., Ltd. , https://www.shangenmetal.com
In certain industrial applications, standard bearings just don't provide the level of precision required. That's where extra precision bearings step in. These bearings offer exceptional tolerance and precision, making them perfect for applications demanding strict requirements for speed (RPM) and guidance accuracy. There are primarily two types of ultra-precise bearings: deep groove bearings and angular contact bearings.
Deep groove bearings feature full shoulders on both sides of the inner and outer ring raceways, which makes it easier to add seals or shields. These bearings can handle radial loads, thrust loads, or a mix of both. They come in numerous sizes, including miniature precision bearings, and are available with different cage types. Extremely versatile, deep groove bearings are among the most commonly used types of bearings.
Angular contact bearings have one complete ring shoulder; the other ring shoulder is partially or fully removed. This design allows them to house larger balls, offering increased load capacity and speed capability. Various cage designs are also available to meet specific high-speed demands. Angular contact bearings can support thrust loads or a combination of thrust and radial loads, but they cannot handle radial loads alone. When installed back-to-back or face-to-face, they can manage thrust loads in both directions.
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Angular contact bearings are available in two main types: separable or non-separable. These classifications depend on whether the outer ring assembly can be detached from the inner ring. Separable angular contact bearings are particularly useful when installing in blind holes or in applications requiring press fits.
When it comes to closures and cages for extra precision bearings, closures are essential to protect against internal damage from handling. For ultra-precise bearings, closures are often made from materials like Teflon or stainless steel. There are two major types of closures for extra precision bearings: shields and seals. Both are designed to keep contaminants out and retain lubrication.
Shields are placed on the inner ring of the bearing, while seals go on the outer ring. Choosing between these two depends on what's more important for your application—sealing efficiency, speed capability, or bearing torque. Shields have lower sealing efficiency but do not increase torque or limit speeds. Seals offer stronger protection but restrict operating speed and increase torque and temperature.
Bearing cages play a crucial role in maintaining uniform ball spacing, reducing torque, and minimizing heat buildup. These cages come in various designs suitable for both deep groove bearings and angular bearings. The choice of cage depends on the specific needs and purpose of the bearing.
Standard precision bearings usually use stamped steel cages. Extra precision bearings, however, utilize cages made from stainless steel, bronze, or phenolic. These materials offer higher speeds and better load-bearing capabilities. Cages can cater to general-purpose needs as well as specialized requirements such as low torque, high speed, lubrication-free operation, and noise control.
All precision ball bearings must adhere to Annular Bearing Engineers Committee (ABEC) standards, which align with ISO standards. ABEC standards establish tolerances for critical bearing characteristics and dimensions, ensuring consistency across the industry.
These guidelines cover parameters such as bore roundness and taper, width variation, bore and race runout, and radial runout. Higher ABEC numbers indicate tighter tolerances—the higher the number, the better the performance. ABEC 1 through 3 bearings are typically for general use, while ABEC 5 through 7 bearings are used for applications needing higher precision and speed. Bearings from higher ABEC precision classes, designed for stationary housings, have rounder balls and smoother raceways.
However, customers shouldn't always opt for the highest ABEC grade. Higher-end bearings can be three to five times more expensive than lower-grade ones. Therefore, it's vital to understand the exact needs of your application to make an informed decision. Often, higher ABEC bearings aren't necessary.
To ensure optimal performance of extra precision bearings, users must set up their systems accordingly. Two key considerations are preloading and radial internal clearance. It's essential to carefully assess these elements to guarantee efficient operation under favorable conditions.
The bearings must have the right amount of radial internal clearance—the total maximum movement possible for the inner ring relative to the outer ring. This is also called "radial play." Proper radial internal clearance is critical because metal expands. Selecting the correct clearance prevents metal ball bearings from seizing in their housings during expansion. Bearings lacking sufficient radial play will fail due to interference and binding.
Preloading involves removing internal clearance from a bearing. Applying permanent thrust load eliminates radial and axial play, creating a very rigid setup. Preloading removes endplay and runout, achieved through spring preloading, axial adjustment, or using duplex bearings.
Duplex bearings are matched pairs of bearings designed to provide built-in preloading. Installed in face-to-face (DB), back-to-back (DF), or tandem (DT) configurations, these bearings counterbalance each other's preload offsets. This enhances axial and radial rigidity and enables them to withstand bidirectional or heavy unidirectional thrust loads.
Shaft and housing fits are also significant when using extra precision bearings. Users should evaluate the bearing's intended application before deciding on the appropriate fit tightness. Looser fits are necessary when axial movement must accommodate spring loading and thermal expansion or when axial clamping forces are involved. Assembly is simpler with looser fits. Tighter fits are ideal when the application requires heat transfer, vibration damping, or support for heavy radial loading.
Finally, users should determine whether extra precision bearings will perform better with grease or oil lubrication. Grease is the standard choice in most scenarios. However, oil should be considered for high-speed applications as it provides better cooling and creates less torque. Oil needs replacement more frequently than grease, which lasts longer without maintenance.
Extra Precision Bearings from Emerson Bearing
Emerson Bearing takes pride in being a leading distributor for many reputable bearing manufacturers. We supply extra precision bearings from top brands such as Barden, GMN, Nachi, NTN, and NSK.
Our team of experts can help you find the right bearing for your specific application and requirements. We can assist in evaluating the various factors discussed above—including navigating ABEC standards—to equip you with the knowledge you need to avoid costly mistakes and downtime.
Get in touch with us today to begin the bearing selection process.
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