At Emerson Bearing, we understand that selecting the right bearing is crucial for the performance and longevity of your machinery. Clearance, preloading, and fit are key mechanical concepts that play a significant role in the function of rolling bearings. In this post, we’ll explore how clearance fits and preloads impact bearing performance and why they matter in your design.
First, it's important to distinguish between initial clearance and operating clearance. Initial clearance refers to the space between the bearing components before installation, while operating clearance is the clearance once the bearing is mounted and has reached its normal operating temperature. For ball bearings, ideal operating clearance should be nearly zero, but for other types like needle, spherical, cylindrical, and CARB toroidal bearings, some radial clearance is necessary to ensure smooth operation and prevent premature wear.
Radial clearance is the amount of play between the rolling elements and the raceway in a direction perpendicular to the bearing axis. Axial clearance, on the other hand, is the play parallel to the axis and is typically much larger—often ten times greater than radial clearance. Both types of clearance have a direct impact on factors such as heat generation, vibration, noise, and overall bearing life.
Bearings are categorized into different clearance groups: C1, C2, CN, C3, C4, and C5. CN represents the standard or "normal" clearance defined by DIN 620 and ISO 5753, suitable for most general applications. Bearings with C1 and C2 clearance have less internal space and are used in precision or low-tolerance environments.
In high-temperature or low-temperature applications, thermal expansion and contraction of the housing and shaft can significantly affect clearance. It’s essential to account for these changes during the design phase to ensure optimal performance and avoid issues caused by improper clearance.
The way a bearing is fitted into your assembly also plays a critical role in its performance. Typically, the inner ring should have a tight fit on the shaft, while the outer ring should be securely seated in the housing. For more detailed guidance on mechanical fits and tolerances, you can refer to standard charts or contact us at Emerson Bearing. Our team is here to help you select the right bearing and ensure it fits perfectly in your system.
Once installed, there should still be a small amount of residual clearance inside the bearing. However, in certain cases, this clearance may not be ideal, and preloading might be necessary. Preloading involves applying a controlled load to the bearing to eliminate any play between the rings. This technique is often used in high-speed applications, machine tools, or automotive axle drives where increased rigidity and stability are required.
There are two main methods of preloading: position preload and constant pressure preload. Position preloading enhances bearing rigidity, making it ideal for applications requiring precise motion control. Constant pressure preload, on the other hand, helps reduce axial vibrations in high-speed systems. The choice between the two depends on your specific application needs.
It’s important to avoid over-preloading, as excessive force can increase friction, energy consumption, and reduce bearing life. If you’re unsure about the best approach for your application, our experts at Emerson Bearing are here to guide you through the process and ensure you get the right bearing for your design.
Whether you're looking for a custom solution or just need help finding the right fit, we’re committed to helping you make informed decisions. Contact us today or visit our Catalog and Technical Toolbox pages to explore our range of high-quality bearings and find the perfect match for your system.
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