Tools & Materials Required
Safety Notes
- Always wear heat-resistant gloves when handling heated bearings
- Never strike a bearing directly with a steel hammer
- Ensure shaft and housing are free of burrs before mounting
- Verify bearing internal clearance after installation
1. Pre-Installation Inspection
Before touching any tooling, inspect the bearing, shaft, and housing thoroughly. Remove the bearing from its packaging only at the point of installation -- exposure to dust or moisture degrades grease fill and corrodes raceways.
Shaft & Housing Checks
- Measure shaft diameter at two axial positions and two radial positions using a calibrated micrometer. Compare readings against the tolerance band on the bearing manufacturer's datasheet.
- Inspect the shaft shoulder for perpendicularity -- a tilted shoulder causes axial misalignment under load, reducing bearing L10 life by up to 50%.
- Verify housing bore roundness. Out-of-round housing bores (more than 0.01 mm difference between max and min readings) cause uneven load distribution on the outer ring.
Bearing Visual Inspection
- Rotate the bearing by hand; it should spin smoothly with no rough spots or clicking.
- Check the packaging for signs of damage, water exposure, or opened seals.
- Confirm the bearing designation matches the engineering specification (e.g., 6205-2RS1 is NOT interchangeable with 6205-2Z).
2. Cold Mounting (Press Fitting)
Cold mounting is suitable for small to medium bearings (bore up to 80 mm) with interference fits up to 0.040 mm. The force is applied through the ring with the interference fit -- typically the inner ring for shaft mounting.
Procedure
Degrease shaft and bearing bore with solvent. Remove any protective oil film from the bearing OD and shaft seating surface.
Lightly oil the shaft seat and bearing bore to reduce friction during pressing. Do not over-lubricate -- excess oil gets trapped and creates hydraulic pressure.
Start the bearing onto the shaft by hand, ensuring it sits perpendicular. A misaligned start causes cocking and potential raceway damage.
Use a fitting tool sleeve that contacts only the inner ring face. Apply steady hydraulic press force -- never impact blows. Press until the bearing seats firmly against the shaft shoulder.
Use a feeler gauge to check the gap between the inner ring face and the shaft shoulder. A gap exceeding 0.05 mm indicates incomplete seating.
3. Hot Mounting with Induction Heater
For bearings larger than 80 mm bore diameter, or interference fits exceeding 0.040 mm, thermal expansion is the preferred mounting method. An induction heater heats the bearing uniformly, expanding the bore enough for easy slide-on assembly.
Temperature Guidelines
| Bearing Bore | Interference Fit | Heating Temperature | Heating Time (approx.) |
|---|---|---|---|
| 30--80 mm | 0.015--0.035 mm | 80--90 C | 3--6 minutes |
| 80--150 mm | 0.025--0.060 mm | 90--110 C | 6--12 minutes |
| 150--300 mm | 0.040--0.090 mm | 100--120 C | 12--20 minutes |
Induction Heater Procedure
Quality induction heaters (SKF TIH series) include an automatic demagnetization cycle. Residual magnetism attracts metal particles that destroy bearing surfaces.
Once heated, you have 15--30 seconds before the bearing cools and shrinks. Have the shaft vertical if possible, and slide the bearing down to the shoulder in one smooth motion.
Apply axial force to keep the inner ring seated against the shoulder while the bearing contracts. Use a locking nut or clamp -- never walk away and assume it stays seated.
4. Hydraulic Mounting (Tapered Bore Bearings)
Tapered bore bearings (suffix K, e.g., 22220 EK) mount on tapered adapter sleeves or tapered shaft seats using hydraulic oil injection. This method provides precise control of drive-up distance and resulting internal clearance reduction.
Drive-Up Method
- Measure the initial radial internal clearance of the bearing using a feeler gauge before mounting.
- Drive the bearing onto the taper using a hydraulic nut or locknut. The drive-up distance (axial displacement) determines the clearance reduction.
- For self-aligning ball bearings, the clearance reduction should be 75--80% of the initial radial clearance.
- For spherical roller bearings, the clearance reduction should be 60--70% of the initial radial clearance.
5. Post-Installation Verification
6. Common Installation Mistakes to Avoid
- Pressing through rolling elements -- Transmitting force through the balls/rollers is the #1 cause of premature failure during installation.
- Overheating sealed bearings -- Heating 2RS bearings above 80 C melts or deforms the rubber seal, creating contamination entry points.
- Skipping shaft measurement -- Assuming the shaft is within tolerance without measuring leads to loose or excessively tight fits.
- Using wrong clearance class -- Installing a C0 (normal) clearance bearing where C3 is specified causes preload under operating temperature.
- Contamination during handling -- Opening bearing packaging too early or mounting in a dusty environment introduces abrasive particles.
- Incorrect lubrication quantity -- Over-greasing causes churning, heat buildup, and grease degradation. Under-greasing causes metal-to-metal contact.
- Misaligned shaft and housing -- Soft foot, non-concentric bores, or tilted shoulders create point loading on one side of the raceway.
- No run-in test -- Starting at full load and speed without a gradual warm-up stresses the grease and can cause early thermal failure.
Pro Tips
- 1Always use manufacturer-specific fitting tools (e.g., SKF TMFT 36) rather than improvised drifts or pipes
- 2Record shaft measurements and clearance readings for each installation -- this data helps diagnose future failures
- 3Store spare bearings in original packaging in a dry, vibration-free area with the sealed side facing up
Important Warnings
- Never reuse a bearing that has been dismounted -- internal stress redistribution makes remounting unreliable
- Do not mix bearing grease types unless compatibility has been lab-verified by the grease manufacturer
Related Topics
Related Products
Continue Learning