How to Mount and Dismount Bearings Correctly — A Practical Guide
Introduction
Incorrect mounting is one of the top causes of premature bearing failure. A bearing that is perfectly greased and correctly selected can still fail within weeks if installed with brute force, uneven heating, or the wrong tool. This guide covers the correct mounting and dismounting methods for the most common bearing types, so your equipment stays online longer.
1. Before You Start — Inspection and Preparation
Before fitting any bearing, inspect the shaft and housing. Check dimensional tolerances with a micrometer — the shaft should be within the specified tolerance range (typically k5/js6 for rotating inner ring, H7 for stationary outer ring). Clean all contact surfaces and remove any burrs with fine abrasive paper. Verify the bearing model, clearance class and grease type against your bill of materials. Never assume the box is correct.
A common mistake at this stage: fitting a bearing without checking shaft roundness. An out-of-round shaft will deform the inner ring after tightening, reducing internal clearance to near zero and causing overheating within hours. TA Bearing recommends checking shaft roundness on every critical installation, especially for spindle and gearbox applications where tolerance stack-up is tight.
2. Mounting Methods
Cold Mounting (Mechanical)
For small bearings (bore diameter up to 40 mm, or light interference fits), cold mounting with a fitting tool and impact ring is acceptable. Never hammer directly on the bearing rings. Use a sleeve that contacts only the ring being fitted — drive the inner ring onto the shaft using a sleeve seated on the inner race, never through the balls or rollers.
Hot Mounting (Thermal)
For bearings with interference fits on the inner ring, induction heating is the standard method. Heat the bearing to 80–100°C (up to 120°C maximum). At this temperature the inner ring expands enough to slip over the shaft by hand. Do not exceed 120°C — overheating damages the grease and can alter heat treatment of the rings.
After heating, mount the bearing squarely against the shaft shoulder and allow it to cool naturally under load. As it cools, the inner ring contracts and locks onto the shaft with the designed interference fit.
Hydraulic Mounting
For large spherical roller bearings, tapered bore bearings, or any bearing mounted on an adapter sleeve, hydraulic nut mounting gives the most controlled result. TA Bearing supplies HMV and HMVC series hydraulic nuts that generate high oil pressure between the sleeve taper and shaft, creating a thin film that virtually eliminates friction. The bearing slides into position with minimal force, and the lock nut is tightened to the specified torque. This method prevents scoring of the shaft and sleeve.
3. Mounting with Adapter Sleeves and Withdrawal Sleeves
Adapter sleeves (AH/H series) are widely used on cylindrical shafts where the bearing has a tapered bore. The procedure:
Slide the adapter sleeve onto the shaft.
Push the bearing onto the sleeve taper.
Tighten the lock nut in small increments while rotating the bearing.
Secure with a locking washer.
Withdrawal sleeves work in reverse — used when the bearing must be mounted close to a shaft shoulder. The sleeve is driven into the bearing bore from the narrow end using a hydraulic nut or mechanical press.
Over-tightening the lock nut reduces internal clearance too much, causing preload and heat. Under-tightening allows creep between sleeve and shaft. Always check residual clearance after mounting with a feeler gauge or dial indicator.
4. Dismounting Methods
For small bearings, a two-jaw or three-jaw puller works — position the jaws behind the inner ring, never behind the outer ring if the inner ring is the interference fit. Apply even tension and tap the shaft end lightly if needed.
For large bearings on adapter or withdrawal sleeves, reverse the hydraulic process: inject oil under high pressure between the sleeve and shaft taper. The oil film separates the mating surfaces and the bearing slides off with minimal force. This prevents damage to the shaft, bearing and housing.
5. Common Mistakes to Avoid
| Mistake | Consequence |
| Hammering the outer ring to fit the inner ring | Brinelling — permanent dent marks in raceway |
| Overheating above 120°C | Grease degradation, possible ring softening |
| Mixing up shaft and housing fits | Inner ring spins on shaft (creep) or outer ring seizes |
| Forgetting to secure the lock nut | Bearing walks off the shaft under load |
| Using dirty tools | Abrasive particles enter bearing, cause early wear |
6. Post-Mounting Checks
After mounting, rotate the shaft by hand. It should turn smoothly with no grating, tight spots or excessive play. For critical applications, check radial and axial clearance with a dial gauge. Run the machine at low speed for 30 minutes, then check temperature. A properly mounted bearing should not exceed 50–60°C above ambient in normal conditions.
Conclusion
Correct mounting and dismounting protects your bearing investment and keeps unplanned downtime off your production schedule. TA Bearing supplies not only the right bearing for your application, but also the full range of accessories — lock nuts, adapter sleeves, withdrawal sleeves and hydraulic nuts — to get the job done right. When in doubt, talk to our engineering team before fitting. One correct installation saves more than one emergency replacement.
