Ball and Roller Bearings - Ntn-snr.com

Technical Data
17.4 Fitting surface pressure
Table 17.4.1 lists equations for calculating the pressure
and maximum allowable stress between fitting surfaces.
Table 17.4.2 can be used to determine the approximate
average groove diameter for bearing inner and outer
rings.
The effective interference, in other words the actual
interference after fitting, is smaller than the apparent
interference derived from the measured valued for the
bearing bore diameter and shaft. This difference is due to
the roughness or variations of the finished surfaces to be
fitted, and therefore it is necessary to assume the
following reductions in effective interference:
For ground shafts: 1.0 2.5m
For lathed shafts : 5.0 7.0m
Table 17.4.1 Fitted surface pressure and maximum allowable stress
Fitted
surface
pressure
MPa
kgf / mm 2
Maximum
allowable
stress
MPa
kgf / mm 2
Fit conditions
Solid steel shaft/
inner ring fit
Hollow steel shaft/
inner ring fit
Steel housing/
outer ring fit
Shaft / inner ring fit
Housing/
outer ring fit
Equation
Codes (units: Nkgf, mm)
d Shaft diameter, inner ring
E ∆deff d 2
bore diameter
P =
1- ( )
2
do
d Di
Hollow shaft inner
diameter
Di Inner ring average groove
diameter
E ∆deff 1- (d / D) 2 1- (d / d) 2 ∆deff Effective interference
P =
2 ∆d
1 - (d / Di) 2 E
Elasticity factor
= 208,000 MPa 21,200 kgf / mm 2
D : Housing inner diameter,
bearing outer diameter
E ∆Deff 1 - (Do / D) 2 1 - (D / Dh) 2 Do : Outer ring average
P =
2 D
1 - (Do /Dh) 2 groove diameter
Dh : Housing outer diameter
∆Deff : Effective interference
1 + (d / Di)2
Inner ring bore diameter face maximum
t max = P
1 – (d / Di) 2
allowable stress
2
t max = P
Outer ring inner diameter face maximum
1 – (Do / D) 2 allowable stress
Do
do
d
D
Di
Dh
Table 17.4.2 Average groove diameter
Bearing type
Average groove diameter
Inner ring (Di ) Outer ring (Do )
Deep groove
ball bearings
All types
1.05
4d + D
5
0.95
d + 4D
5
Cylindrical
roller bearings 1
All types
1.05
3d + D
4
0.98
d + 3D
4
Spherical
roller bearings
All types
2d + D
3
0.97
d + 4D
d: Inner ring bore diameter mm D: Outer ring outer diameter mm
1 Average groove diameter values shown for double rib type.
5
A-98