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Maintenance knowledge: Bearing mounting -
Mechanical
bearing mounting |
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Mechanical mounting is generally suitable for small bearings. Mounting force
can be applied to the bearing by placing a fitting tool impact ring and sleeve
against the inner ring and using a press or hammer to advance the bearing to its
proper location on the shaft. Be sure the correct size impact ring and sleeve
are selected from a bearing fitting tool kit, such as the SKF TMFT 33 fitting
tool kit. The bearing should be exactly at right angles to the shaft before
beginning, and the shaft lightly lubricated.
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| 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. |
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| Raceway damage incurred when a bearing is
incorrectly mounted can result in premature bearing failure. Typical
problems, which can cause premature failure, are: |
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Damage caused during the fitting procedure |
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Incorrect sized shafts and housings i.e. too
loose or too tight |
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Retaining lock nuts becoming loose during
operation |
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Burred and damaged shaft and housing seats
and shoulders |
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Incorrectly mounted bearings |
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| Cylindrical shafts -
interference fits |
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Most bearings are fitted to their shaft or housing with one component having
an interference fit or in some cases both. For determining the correct fit,
refer to the SKF General Catalogue, the SKF Maintenance Handbook or consult an
SKF application engineer. |
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| Incorrect mounting |
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When bearings are mounted cold, care must be taken to ensure that the
drive-up forces are applied to the ring with the interference fit. Damage and a
resulting bearing failure can occur if the mounting force is transmitted through
the rolling elements causing damage to the raceways. |
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| Correct mounting |
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The correct way to minimise raceway damage is to use the specifically
designed tools from SKF - the TMFT fitting tools series. These tools ensure that
the drive-up forces are applied effectively and evenly to the ring with the
interference fit avoiding raceway damage.
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| A |
Shaft interference fit |
| B |
Housing interference fit |
| C |
Uneven distribution of forces can
result in raceway damage |
| C |
With the correct tools raceway
damage is avoided |
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Tapered shafts -
interference fits |
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Bearings mounted on tapered seatings, adapter sleeve or withdrawal sleeve
achieve their interference fit by being driven up the tapered shaft. Care should
be taken to ensure that the bearing is not driven up too far as all the internal
clearance may be removed, which can result in bearing damage.
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| Spherical roller bearings |
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Method:
Correct adjustment of spherical roller bearings is determined by measuring the
residual internal clearance in the bearing or by the amount of axial drive-up. |
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| A |
Correctly mounted: Bearing driven
up the correct distance and the right clearance is achieved |
| B |
Incorrectly mounted: Bearing is
driven up too far and all clearance removed: damage possible |
| C |
Before adjustment |
| D |
After adjustment |
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Self-aligning ball bearings
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Method:
Adjustment of double row, self-aligning ball bearings to obtain a correct
interference fit is more difficult to achieve than spherical roller bearings
because the feeler gauge method cannot be used. The most effective method to
adjust this type of bearing correctly is to use the SKF TMHN 7 lock not spanner
set. |
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| A |
Correctly mounted: Bearing driven
up the correct distance and the right clearance is
achieved |
| B |
Incorrectly mounted: Bearing is
driven up too far and all clearance removed: damage possible |
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| For more information on SKF fitting tools, please see our Mechanical Tools
FAQ section or our online catalogue on this
site |
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