PROPER BEARING MOUNTING
HELPS PREVENT CRACKS FLAKING OTHER DAMAGE
How rolling bearings are mounted has a direct impact on their service life. If you use correct mounting methods and observe a few simple precautions, your bearings are far more likely to deliver maximum performance. Mount bearings improperly. And you may experience premature bearing failure.
Cleanliness: The First Rule
Cleanliness is the first rule of proper bearing handling. Whenever possible, keep the working environment clean of sand, sawdust, cement, corrosive substance and, wherever possible, high humidity. Prior to installing a bearing, clean the shaft and housing with a solvent and dry thoroughly using a clean, lint-free cloth. Cover exposed area with plastic sheeting or lint-free cloth when you are not working with the bearing.
New bearings should be keep in their packaging until just before mounting. Do not wash new bearings or remove the rust-inhibiting compound, except from the bore and the outer ring's surface. Wash these with a petroleum-based solvent and dry with a clean cloth.
Thoroughly inspect used bearings for damage prior to installation, and clean them with solvent or hot cleaning oil (not more than 250°F).
Lubricant should be clean and fresh. Keep lubricant containers closed until needed. Use the right type and quantity- contaminated lubricants, or incorrect lubricant amounts, can cause early bearing failure (See the following articles for more information about lubrication).
Check Shaft Preparation
Prior to mounting a bearing, check to ensure that the shaft size is within its specified tolerances. The bearing seat should be perfectly round, and not tapered, the shaft should be clean and free form nicks and burrs. Inspect the shaft for damage that may have occurred when the previous bearing was dismounted.
Use Different Mounting Methods
There are four basic methods for mounting bearings: mechanical, heating, hydraulic and oil injection. The correct method depends on bearing type and size.
Mechanical mounting is generally suitable for small (4" or less O.D.) bearings. Mounting force can be applied to the bearing placing a fitting tool sleeve against the inner ring and using a press or hammer to advance the bearing to its proper location on the shaft. Be sure to use the correct size sleeve from a bearing fitting tool kit, or a pipe sleeve of the proper dimensions. The bearing should be exactly at right angles to the shaft before beginning, and the shaft lightly lubricated.
Do not apply a sleeve to the outer raceway when mounting on a shaft, or to the inner raceway when mounting in a housing- and NEVER mount by striking the bearing directly with a hammer.
A spanner wrench or impact spanner and lock nut can be used to cold-mount small and medium-size bearings with tapered seatings, such as adapter sleeve arrangements.
Heat mounting is suitable for all medium and large size bearings, and for small bearings with cylindrical seating arrangements. Normally a bearing temperature of 150°F above shaft temperature (not to exceed 250°F) provides sufficient expansion for mounting. As the bearing cools, it contracts and tightly grips the shaft. It's important to regulate heat accurately, since excess heat destroys a bearing's metallurgical properties, softening the bearing.
Heat mounting tools include induction heaters, ovens, heating rings and electric plates with thermostats. Never heat a bearing using an open flame, such as a blowtorch.
Hydraulic mounting uses hydraulic pressure instead of mechanical force. A hydraulic ram will mount small bearings with tapered bores; a hydraulic nut is recommended for bearings with bore diameters over 50 mm.
The oil injection method, which is sometimes used in conjunction with hydraulic bearing mounting tools, is suitable for all bearings having tapered seating arrangements and for large bearings with withdrawal or adapter sleeves. Oil injection forces oil under high pressure through a passage between the shaft and the bearing inner ring to separate the two, which makes mounting easier by reducing friction to almost zero.
Although care has been taken to ensure the accuracy of this data, SKF assumes no liability for errors or omissions.
SKF is a registered trademark of SKF
1998 SKF USA Inc.
The above information was supplied by the SKF USA, Inc. The SKF Bearing Maintenance Institute recommends the above bearing maintenance tips to maximize bearing performance. SKF USA, Inc. may be contacted at www.skfusa.com. Proper Bearing Mounting