MOUNTING OF BEARING ON SHAFTS

MOUNTING OF BEARING ON SHAFTS

1. Setscrew method

This method is to mount the bearing unit to the shaft with two set screws located at two places on one side of wide inner ring which make 120°each other.
Our setscrews are of self-locking knurled cup point types. This self-locking knurled cup point type setscrew has peculiar edge points as shown in the figure and counter-clockwise knurl to prevent loosing back. The material is special alloyed steel (Nickel chromium molybdenum steels) which has high tensile and shear strength. The hexagon hollow of setscrew is deeper than before and hence enough tightening force can be applied. The head is never broken nor deformed.
Installation to the shaft can be sufficiently made, if the grub screws are tightened by application of the tightening torque as shown in the following table.

Proper tightening torque of setscrews

 In case either the vibration is caused to the bearing, the reciprocal movement takes place, the load charged on the bearing is large, or the shaft revolution speed is rapid, then it is desired to provide with the filed seat or concave section at the part where the setscrews with the shast. If the thrust load is large, it is more effective to use joggling tightened with nuts.

 2.  Adapter assembly method
According to this system, the inner ring diameter of bearing has the taper of 1:12. Prior to the bearing installation the sleeve is installed to an arbitrary position as shown in the drawing. After the shake-proof washer is inserted, the nut is tightened. 
“The proper nut tightening condition can be obtained if it is tightened enough by a hand and is then rotated by 2/5~3/5 revolution with a spanner”.
After the nut is tightened, bend the shake proof washer within the slot. If not, the nut may be loosened and the creep may be caused between the shaft and sleeve.
If tightened too hard, the clearance between the shaft and the sleeve may be reduced, and the exothermic and burning phenomenon may be caused.

3.  Eccentric locking collar method

The bearing installation to the shaft by using the eccentric locking collar is one of the methods. The eccentric part of the collar mates with section of inner ring, and in this way, the bearing is locked to the shaft.
In the normal hexagonal hollow setscrew or adapter assembly case, the shaft and inner ring are simply locked. Different from such a method, the revolving force of shaft is utilized as the tightening force in this case.
The assembly to the shaft is done only by tightening the eccentric locking collar to the shaft by use of the setscrew.
The tightening force of the setscrew can be the same level as that of common setscrew type. Since the shaft revolution force or load does not directly act on the setscrew, the setscrew is not loosened.

4. Axial movement due to expansion and shrinkage

It is often that under some driving conditions the shaft expands or shrinks, the bearing is moved.
The wheel shafts of truck, for example, must be moved in thrust direction while to some extent. When the shaft is used at high temperature, the thermal expansion of shaft becomes larger as the shaft is longer. If the all bearing are fixed to the shaft in this case, an extraordinary thrust load is applied to the bearings due to thermal expansion and it may cause failure of the bearings.
For this reason, if there exist expansion and shrinkage of shaft or movement of bearing, as fixed type unit must be used at one and a moving type unit at the other.

5. Mounting method of housings

It is desired to install the unit in the order of  housing   ==>  shaft and bearing.
The bearing unit can be installed in principle at any place in an easy way. However, in order to have the long service life, it is desired that mounting base is flat and rigid. The mounting base should have in principle the bearing center alignment angle of less than ±3°, when the unit is installed there. In the case of the unit with covers the bearing center alignment angle should be lee than ±1°from point of view of covers used.

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