Warning: Improper installation is the leading cause of bearing failure and premature wear!
Even the highest quality bearings will suffer reduced performance, shortened lifespan, or immediate failure if 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 due to improper installation. The following points should therefore be carefully observed.
Selection of the Fit
The proper functioning of the ball bearings largely depends on the quality of the fit. Selecting the correct fit (tolerance fit between shaft and housing) is crucial for bearing performance.
Key Factors Affecting Fit Selection
| Factor | Considerations | Recommendations |
|---|---|---|
| Surface Quality | Roughness of shaft and housing | Ra <= 0.8 um (Ra <= 0.4 um recommended for precision applications) |
| Temperature Variation | Difference between operating and ambient temperature | Consider thermal expansion when temperature difference is large, adjust fit accordingly |
| Load Type | Radial, axial, combined loads | Heavy loads require tighter fits, light loads allow looser fits |
| Load Direction | Load acting on inner or outer ring | Load-carrying ring uses interference fit, non-load ring uses 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 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 Recommendations:
- Inner ring: Interference fit (k6, m6, n6)
- Outer ring: Clearance fit (G7, H7)
Typical applications: Motors, pumps
Outer Ring Rotating Load
Fit Recommendations:
- Inner ring: Clearance fit (g6, h6)
- Outer ring: Interference fit (K7, M7, N7)
Typical applications: Conveyor rollers
Indeterminate Direction Load
Fit Recommendations:
- Both rings use interference fits
- Or conduct detailed load analysis
Typical applications: High vibration environments
Manufacturing Tolerances for Shafts and Housings
To ensure proper fit, shafts and housings must be manufactured to specified tolerances. The following are recommended tolerance grades:
Recommended Shaft Tolerances
| Load Condition | Tolerance Grade | Fit Type | Application Examples |
|---|---|---|---|
| Light load, inner ring rotating | g6, h6 | Clearance fit | Small motors, instruments |
| Normal load, inner ring rotating | j6, k6 | Transition fit | General mechanical equipment |
| Heavy load, inner ring rotating | m6, n6 | Interference fit | High load applications |
| Outer ring rotating | g6, h6 | Clearance fit | Conveying equipment |
Recommended Housing Tolerances
| Load Condition | Tolerance Grade | Fit Type | Application Examples |
|---|---|---|---|
| Inner ring rotating | G7, H7 | Clearance fit | Standard applications |
| Light load, outer ring rotating | J7, K7 | Transition fit | Light equipment |
| Normal load, outer ring rotating | M7, N7 | Interference fit | General machinery |
| Heavy load, outer ring rotating | P7 | Heavy interference fit | Heavy machinery |
Special Considerations for High Temperature Applications
High Temperature Application Recommendations:
For applications with operating temperatures exceeding 100°C or complex working conditions, myonic strongly recommends laboratory testing to verify fit selection and bearing performance.
- Thermal expansion affects fit tightness
- Different materials have different thermal expansion coefficients
- Looser fits at room temperature may be required
- Finite Element Analysis (FEA) simulation is recommended
The tolerances are given in um and only apply if the material for the shafts and housings has the same coefficient of expansion as the steel used for the ball bearings. In all other cases, the different expansion values must be taken into account.
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 Proper Tools
Use dedicated bearing installation tools. Never transmit installation force through the rolling elements.
3. Apply Force Evenly
Force must be evenly distributed around the entire ring circumference during installation. Avoid tilting.
4. Temperature Control
For interference fits, you can heat the bearing or cool the shaft. Avoid using open flames.
5. Check Alignment
After installation, verify that the bearing is properly positioned. Rotation should be smooth without binding.
Adhesive Mounting
For some light load applications or situations where interference fits cannot be used, adhesive bonding is an effective installation method. myonic recommends using anaerobic adhesives (such as Loctite) for securing.
Recommended Adhesive Specifications (Loctite Series)
| Loctite Type | Characteristics | Typical Applications | Recommended Gap |
|---|---|---|---|
| 638 | High strength, fast curing | Standard installation, high torque transmission required | 0.01 - 0.05 mm |
| 648 | High strength, high temperature resistant | Bearings operating in high temperature environments | 0.01 - 0.05 mm |
| 290 | Wicking Grade | Post-assembly application | Micro gaps |
Curing Time
- Handling Strength: 30 - 60 minutes
- Full Strength: 24 hours (recommended standing time)
Surface Preparation
- Cleaning: Use lint-free cloth
- Degreasing: Use volatile solvents (such as Benzine or alcohol) to thoroughly remove oil
- Drying: Ensure surface is completely dry before applying adhesive
Adhesive Mounting Precautions
- Irreversibility: Adhesive bonding is usually permanent and difficult to disassemble for replacement.
- Contamination Risk: Adhesive quantity must be precisely controlled. Adhesive must never enter the bearing raceway.
- Fit Gap: Gaps that are too large will reduce bonding strength, while gaps that are too small may prevent even adhesive distribution. Recommended range: 0.01 - 0.05 mm.
Laboratory Testing Services
Laboratory tests are often required to find the best solutions. The installation and operating conditions are important here. Such tests can be carried out in the myonic laboratory.
For easier installation, myonic ball bearings can be classified on delivery according to dimensional groups of the bore and/or outside diameter.
If you have any questions about design or installation, please contact the myonic technical support team.
Our engineers have extensive experience with miniature bearing applications and can provide professional technical guidance and customized solutions.