Bearing match
Match of rolling bearing
In order to prevent the skidding operation when the bearing inner ring, shaft, bearing outsider ring and bearing shell hole generated in the machine. In order to choose the right match, we must consider the type and size of load, bearing type and other perfomance requirement.
cylindircal bore bearing in choice of bearing mach, should consider following factors:
1.Load type
according to the load acting on the bearing related to rotation on the bearing ferrule, the load role in the ring can be divided into: fixed load, rotary load and swing load.
(1) Fixed load
Role in the ring synthesize radial load, is supported by the local area of raceway, and spread to the relative bearing shaft or local area, this load is call fixed load. The characterized of fixed radial load is static load synthesis by load vector and ferrule. We can choose the light match when the ferrule with a fixed load.
(2) Rotary load
Role in the ferrule synthesis of radial load vector rotate on the raceway along the circumferentia, sequential manner by the various parts of the racway to bearr this load is called rotary load,also known as cyclic loading. Rotary load characterized by a synthesis of ring radial load vector and the relative rotation.
Ferrul, shaft or housing hole which endure a revulation load should use interference match. If installation with space, ferrul with shaft or shaft with housing hould may occer the phenomenon of slipping, the contact face will wear and friction, and friction heat due to the rapid temperature ris, bearing will be damaged quickly. the amount of interference is not depend on the operation situation, to bearing under the load of operation, the ferrule hole in the shell co-axis or the surface is not a "crawing" as a principle.
(3) Swing load
Synthetic radial load vector role on the ferrule oscillation within a certain range in the raceway by the roller to bear a certain range, or the load acting on the bearing is impact load, vibration load, its direction or value changes frequently, this load called oscillation load, or variable direction load.
when bearing bear a swing load, especially bear a heavy load, the inner ring and outer ring should use a interference match. When the inner ring rotating, usually inner ring with a rotating load match.but when it bears a light load, can use a match loose than rotating load.
2.The size of load
The load of bearing ferrule is acting by the radial component will be compressed in the radial direction would causing the surface relaxation, in the case of load transfer back easy to produce skidding. Therefore, for heavy duty situations should normally be higher than in the more load and normal load occasions with the tight schedule. Load, the greater the amount of interference with the greater should be.
when radial load points"light", "normal" and "heavy" load, generally have the relationship listed in table 10.(Cr show the basic dynmic load of bearing)
Table 10 Equivalent dynamic load, the relationship between Pr and Cr
Radial load |
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Ball bearing |
Roller bearing(Except tapered roller bearing) |
|
Light load |
Pr≤0.07Cr |
Pr≤0.08Cr |
Normal load |
0.07Cr<Pr≤0.15Cr |
0.08Cr<Pr≤0.18Cr |
Heavy load |
Pr>0.15Cr |
Pr>0.18Cr |
3.Working temperature
When the bearing in operation, the ring temperature is usually higher than the temperature of the adjacent parts of the bearing, the inner ring may be loose due to expansion with the axis, the outer ring may be affected due to thermal expansion of the axial bearing swimming. Therefore, the choice must take into cosideration with the temperature difference and the direcion of the thermal conductivity.
4.Bearing rotation accuracy
When it's required of the rotation of the bearing accuracy and smooth operation, in order to eliminate the impact of elastic deformation and vibration, to avoid using clearance fit.
5.The design and material of shaft and bearing housing
If the shaft or bearing housing surface is irregular, will result in the inner ring and our ring of bearing not normal deformation, and asymmetry damaged force. For the open type bearing, the match of bearing outer ring and housing can not use interference match, but the outer ring should either run in the housing hole.When the bearing installed in the thin, ligh alloy bearing housing or the hollow shaft, in order to ensure adequate bearing surface, should use a match tighter than the it used in thick housing, cast iron or soild shaft.
Radial bearing with shaft tolerance zone, it is recommended to select from the table 11
Table 11 Install the centripetal bearing with the shaft tolerance
Inner ring operation condition |
Application examples |
Deep groove ball bearing, self-aligning ball bearing and angular contact ball bearing |
Self-aligning roller bearing |
Tolerance zone |
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Rotation condition |
Load |
d(mm)/Bearing metric insider diameter |
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Inner ring swing or rotate relative to the direction of the load |
Light load |
Electrical instrument, machine tools(spindle) precison mechanical pump, fan belt |
d≤18 |
- |
h5 |
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18<d≤100 |
d≤40 |
j6① |
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100<d≤200 |
40<d≤65 |
k6① |
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- |
100<d≤200 |
m6① |
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Normal load |
Normal general machinery, electric motors, turbines, pump, engine, gear box, woodworking machinery |
d≤18 |
- |
j5、js5 |
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18<d≤100 |
d≤40 |
k5② |
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100<d≤140 |
40 <d≤65 |
m5② |
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140<d≤200 |
65 <d≤100 |
m6 |
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200 <d≤280 |
100<d≤140 |
n6 |
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- |
140 <d≤280 |
p6 |
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Heavy load |
Oil box for railway vehicles and trolley, traction motors, mills, crushers and other heavy machineries |
- |
50<d≤100 |
n6③ |
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- |
100 <d≤140 |
p6③ |
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- |
140<d≤200 |
r6③ |
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- |
d>200 |
r7③ |
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Inner ring quiescence relative to the direction of the load |
All load |
Inner ring must easy to move in the axial direction |
Various rollers on the quiescence bearing |
All dimension |
f6、g6① |
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Unnecessary to move in the axial direction |
Pulley tensioner, |
All dimension |
j6、h6① |
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Pure axial load |
All situations |
All application situations |
All dimension |
j6 OR js6 |
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Taper bearing(with concial cover) |
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|
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All load |
Oil box for railway vehicles and trolley |
All size installed in the bushing |
h8④ |
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Normal general mechinery or transmission shaft |
All size installed in the adapter sleeve |
h9 |