Timken Spherical Roller Bearing Catalog

ENGINEERING
MOUNTING, FITTING, SETTING AND INSTALLATION
EXAMPLE #2 – continued
For the primary selection of RIC, the major parameters are the
bearing speed and the fits. For our example, we know that the
shaft fit is 0.043 mm (0.0017 in.) tight to 0.093 mm (0.0037 in.) tight.
We know the housing fit is 0 mm to 0.116 mm (0.0046 in.) loose.
We also know that the bearing speed is 1200 RPM or 60 percent
of the speed rating.
As a general rule of thumb, we bump the clearance up to
operating speeds that exceed 70 percent of the speed rating, due
to concerns over internal heat generation and thermal growth.
In this case, we are at 60 percent of the speed rating, so normal
clearance, ISO C 0 or C o , can be selected.
Observing the RIC chart on page 19, we find for 150 mm nominal
bore at C o , the RIC will be 0.110 mm to 0.170 mm (0.0043 in. to 0.0067
in.). We also note that the minimum recommended RIC (installed)
is 0.056 mm (0.0022 in.).
Also from page 19, we note that we get an approximate reduction
of RIC that is 80 percent of interference fit on a solid shaft and 60
percent of the O.D. interference fit in a steel or cast iron housing.
Since we have a loose housing fit, there will be no RIC reduction
from that fit.
Shaft fit RIC reductions and clearance:
For a 150 mm nominal bore at C3, the RIC will be 0.115 to
0.165 mm (0.0045 to 0.0065 in.). Recalculating shaft fit RIC reduction
and clearance:
max. clearance
min. clearance
= max. RIC - min. fit reduction
= 0.165 - 0.034 = 0.131 mm (0.0052 in.)
= min. RIC - max. fit reduction
= 0.115 - 0.074 = 0.041 mm (0.0016 in.)
Since the minimum mounted clearance is less than the minimum
suggested RIC of 0.056 mm (0.0022 in.), the C3 RIC clearance limit
needs to be reevaluated.
22 TIMKEN SPHERICAL ROLLER BEARING CATALOG