The radial clearance values for this bearing model are as follows (in micrometers, um):
1. Why Do Bearings Need "Clearance"?
You might think that the tighter a bearing fits, the better it performs. However, that’s not the case. Bearings require a specific amount of internal clearance to handle two main issues:
Thermal Expansion: Bearings generate heat during operation, causing the metal components to expand. Without enough clearance, this expansion would cause the bearing to seize or "lock up."
Interference Fit: When a bearing is pressed onto a shaft, the inner ring stretches slightly. This physical expansion "consumes" a portion of the original internal clearance.
2. Bearing Clearance Ratings (ISO 5753)
Bearing clearance is typically categorized by the following common levels: C2, C0 (Normal), C3, and C4.
3. When to Choose C2, C0, C3, or C4?
The core logic for selecting a clearance grade is to predict how much "residual clearance" will remain while the bearing is running.
Once installed, the original clearance decreases due to the tight fit and thermal expansion. If the clearance is too small, the bearing will overheat and fail; if it is too large, it will cause vibration and eccentricity.
Here is a selection guide for different working conditions:
1. Choosing C2 (Small Clearance)
Goal: High precision and low vibration.
High Rotational Accuracy: For applications requiring the shaft to be perfectly centered with no "play."
Low Noise: To further suppress vibration in precision small motors.
Operating Conditions: Very precise (light) fits and minimal temperature rise during operation.
Common Applications: CNC machine spindles, small stepper motors, and office automation equipment.
2. Choosing C0 (Standard Clearance) — The Default
Goal: General-purpose balance.
Standard Conditions: Used when the inner ring and shaft have a standard fit, and the outer ring is not overly tight in the housing.
Moderate Temperature: The temperature difference between the bearing and the environment is within 30°C to 50°C
Common Applications: Home appliances, water pumps, gearboxes, and most general machinery.
3. Choosing C3 (Large Clearance) — The Industrial Standard
Goal: Accommodating thermal expansion and tight fits.
Interference Fits: Used when a tight fit is needed to prevent the inner ring from slipping on the shaft; the resulting "expansion" consumes the extra clearance.
High Heat / High Speed: Fast rotation generates friction heat, causing the balls and rings to expand rapidly.
Large Temperature Gradients: When the bearing's operating temperature is significantly higher than the housing temperature.
Common Applications: Industrial motors, automotive wheel hubs, AC compressors, and high-speed centrifuges.
4. Choosing C4 / C5 (Extra Large Clearance)
Goal: Extreme high temperatures.
High-Heat Environments: For bearings in kilns, industrial dryers, or papermaking machines where metal expansion is extreme.
Heavy Shock Loads: When heavy loads might cause slight shaft deformation.
Common Applications: Kiln cars, continuous casters, vibrating screens, and large power generators.
