Needle Roller Bearings - Ntn-snr.com

Bearing Handling
NTN
the bearing fixing method.
Regarding the dismounting method, generally the press
method (Fig. 10.4) and the puller method (Fig.10.5) are
available for dismounting inner ring though depending on
bearing type and fitting conditions.
When inner ring is dismounted from a shaft by heating,
good care must be exercised not to over-heat the inner ring.
d
f E B1 2
F1
B Inner ring width mm
d Inner ring bore diameter mm
F1 Mean outer diameter of inner ring mm
dFApparent interference m
Actual press-fit force and pull-out force could eventually
exceed the respective calculate value due to installing
error. Hence, it is recommended to design the
dismounting tools so as to have the strength (rigidity)
resistible to a load 5 times as much as the calculated
press-fit force and pull-out force.
Fig. 10.4 Bearing removal by a press machine
10.6 Washing
Rotating a bearing with foreign matter adhered thereto
could result in damage of the raceway surface, etc.
Therefore, any dismounted bearing is usually washed by
light oil or kerosene or the like for complete removal of
foreign matter. In this case, two washing vessels must be
used as follows; one for rough washing and another for
finish washing. Rough washing is done for removal of oil
and foreign matter from bearing, while finish washing is
done for fine washing of the roughly-washed bearing.
Further, any vessels used for washing must be provided
with a steel net as the middle bottom above the vessel
bottom, as illustrated in Fig. 10.6, to prevent the bearing
from coming in direct contact with the vessel bottom.
Furthermore, rust preventive treatment must be applied
to the washed bearing immediately after washing, to
thereby protect it from a risk of corrosion.
In addition, the legal requirements as applicable
(environmental preservation, industrial labor safety and
health, etc.) and the washing specification submitted from
a detergent manufacturer must be taken in consideration
in washing.
Fig. 10.5 Bearing removal by a puller
10.5 Force required for press-fit and pull-out
The force required for press-fitting or pulling out inner
ring on / from a shaft can be determined by formula
(10.1).
d
Kaf K f E d F (10.1)
d3
Where,
Ka Force required for press-fitting or pulling-out N (kgf)
f K Resistance factor being determined by shaft to
inner ring friction factor
For press-fitting 40 (4)
For pulling-out60 (6)
Coefficient depending on inner ring dimension
f E
Fig. 10.6 Washing tank
A-51