Important: Improper installation is the leading cause of bearing failure and premature wear.
Even the highest-quality bearings will suffer reduced performance, a shortened service life, or even immediate failure if they are not installed correctly.
Miniature ball bearings can only perform their function properly if they are installed correctly. Experience has shown that malfunctions and excessive wear are in most cases caused by improper installation. The following points should therefore be carefully observed.
Selection of the Fit
Selecting the correct fit (the tolerance fit between the shaft and the housing) is crucial for bearing performance. Several factors must be considered when selecting the fit:
Key Factors Affecting Fit Selection
| Factor | Key Consideration | Explanation |
|---|---|---|
| Surface quality | Roughness of the shaft and housing | Affects the friction torque and running noise; must comply with the tolerances specified in the catalogue |
| Temperature variation | Difference between operating and ambient temperature | When the temperature difference is large, thermal expansion must be taken into account and the fit adjusted accordingly |
| Load type | Radial, axial, combined loads | Heavy loads require a tighter fit; light loads allow a looser fit |
| Load direction | Load acting on the inner or outer ring | The loaded ring uses an interference fit; the non-loaded ring uses a clearance fit |
| Precision requirements | Rotational accuracy and rigidity needs | High-precision applications require stricter fit tolerances |
Type, Direction and Magnitude of Loads
Relative Motion of the Inner and Outer Rings
Determining which bearing ring rotates relative to the load is key to selecting the proper fit:
Inner Ring Rotating Load
Fit recommendation:
- Inner ring: interference fit (press fit)
- Outer ring: clearance fit (sliding fit)
Typical applications: motors, pumps
Outer Ring Rotating Load
Fit recommendation:
- Inner ring: clearance fit (sliding fit)
- Outer ring: interference fit (press fit)
Typical applications: conveyor rollers
Indeterminate Direction Load
Fit recommendation:
- Both rings use an interference fit
- Or carry out a detailed load analysis
Typical applications: high-vibration environments
Manufacturing Tolerances for Shafts and Housings
The myonic official tolerances are given as values in μm (see myonic Standard Catalogue pp. 25-26). The following data is taken from the official documentation: positive values indicate interference, negative values indicate clearance.
Shaft Tolerances
| Load / Speed Condition | Fit Type | Tolerance (μm) | Precision | Typical Application |
|---|---|---|---|---|
| Low load, low to medium speed, no vibration | Sliding fit | -5 to -8 | Normal accuracy | Guides, brakes |
| Medium load, medium speed, high-frequency vibration | Press fit | 0 to -3 | Precise radial rigidity | Gyroscopes |
| Low load, medium speed, low-frequency vibration | — | -6 to -3 | Normal accuracy | Small motors, servos |
| High load, high speed, high-frequency vibration | Press fit | +4 to +1 | High radial rigidity | Fans, motors |
| Medium to high load, high speed, high-frequency vibration | — | -2 to +1 | — | — |
Housing Seat Tolerances
| Load / Speed Condition | Fit Type | Tolerance (μm) | Precision | Typical Application |
|---|---|---|---|---|
| Low load, low to medium speed, no vibration | Sliding fit | +5 to +2 | Normal accuracy | Motors, fans |
| Medium load, medium speed, high-frequency vibration | Press fit | 0 to -3 | Precise radial guidance | Synchronous motors |
| Low load, low to medium speed, low-frequency vibration | — | -6 to -3 | Normal accuracy | Guides, tension pulleys |
| High load, high speed, high-frequency vibration | Tight fit | -3 to -6 | Tight fit ensured at high speed | Rollers, planetary gears |
| Medium to high load, high speed, high-frequency vibration | Tight fit | -9 to -6 | High rigidity | — |
Special Considerations for High Temperature and Complex Operating Conditions
Recommendation for complex operating conditions:
For applications with complex operating conditions, myonic recommends laboratory testing to verify the fit selection and bearing performance.
- Thermal expansion affects the tightness of the fit
- Different materials (such as light-alloy housings and steel shafts) have different coefficients of thermal expansion
- A looser fit at room temperature may be required to compensate for thermal expansion
Installation Best Practices
1. Maintain Cleanliness
Work in a dust-free environment, use lint-free gloves, and prevent any contaminants from entering the bearing.
2. Use the Correct Tools
Use dedicated bearing installation tools, and never transmit the installation force through the balls.
3. Apply Force Evenly
During installation, the force must be evenly distributed around the entire circumference of the ring to avoid tilting.
4. Temperature Control
For interference fits, the bearing can be heated or the shaft cooled; avoid using an open flame.
5. Check Alignment
After installation, check that the bearing is correctly positioned; rotation should be smooth and free of binding.