NTN - Precision Rolling Bearings

Technical Data
To avoid deformation of the outer ring raceway
surface, NTN recommends that the outer ring be
installed to a highly accurate housing in transition fit
with a large number of bolts.
1
12(= 0.01 to 0.02 mm is recommended)
2
Locked with bolt
Deterioration in roundness of
raceway surface (m)
3
2
1
0
Fit: 5 m loose
Bolt tightening torque: 2 kN-cm
Bolts, 2 pos.
Bolts, 6 pos.
0.01 0.02 0.03 0.04 0.05
Pressing allowance on outer ring (mm)
Front cover
Fig. 6.15 Pressing allowance on outer ring vs.
deterioration in roundness of raceway surface
Fig. 6.12 Front cover pressing allowance
6 Checking axial rigidity
In the typical method for checking for the axial rigidity
of a bearing installed to a machine tool, the main
spindle itself is pushed with a push-pull gage to
measure the resultant axial displacement. A method
using a dial indicator is described below.
Two dial indicator are placed on two locations
(axisymmetric locations separated by 180˚) at the
leading end of the main spindle. Use magnetic stands
to secure the dial indicator to the end face of housing.
Then, apply the load onto the main spindle and the
resultant axial displacement is measured.
Fig. 6.13 Measuring position for roundness on outer
ring raceway surface
Shaft end of
main spindle
Dial indicator
Hydraulic cylinder
Deterioration in roundness
of raceway (m)
8
7
6
5
4
3
2
1
0
Pressing amount on outer ring: 0.05 mm
Bolt tightening torque: 2 kN-cm
Bolts, 2 pos.
Bolts, 6 pos.
3 0 5 9 12
Fitting amount allowance between bearing
outside surface and housing (m)
Dial indicator
Photo 6.3
Fig. 6.14 Effect of fit of outer ring on roundness of
raceway surface
Measuring load
(push-pull gage
etc.)
Dial indicator
Dial indicator
Fig. 6.16 Checking for axial rigidity
32