Needle Roller Bearings - Ntn-snr.com

Bearing Accuracy
NTN
4. Bearing Accuracy
The dimensional, profile and running accuracies of
rolling bearings are specified in ISO Standard as
applicable and JIS B 1514 (Accuracy of Rolling Bearings).
"Dimensional accuracy" and "Profile accuracy" are
the items indispensable in installing the rolling bearings on
a shaft and in a bearing housing, and allowable bearing
run-out in running is specified as the running accuracy.
Dimensional accuracy:
Dimensional accuracy means the respective allowable
values for bore diameter, outer diameter, width or height
(limaited to thrust bearing) and chamfering dimension.
Profile accuracy:
This means the allowable value for variation of each of
bore diameter, mean bore diameter, outer diameter,
mean outer diameter, and width or thickness of bearing
ring (limited to thrust bearing).
Running accuracy:
This means the respective allowable values for radial
run-out and axial run-out of both inner ring and outer ring,
lateral run-out of inner ring, and outer diameter run-out of
outer ring.
Regarding the accuracy class of the machined ring
needle roller bearings, class-0 is equivalent to bearings of
the normal precision class, and precision becomes
progressively higher as the class number becomes
smaller; i.e. Class 6 is less precise than Class 5, which is
less precise than Class 4, and so on.
Bearings of Class-0 are mostly used for general
application, while bearings of Class-5 or Class-4 are
used, where the required running accuracies and
revolutions are high or less friction and less fluctuation
are required for bearings.
Various bearing types are available for NTN needle
roller bearings and the representative types and the
accuracy classes applicable to them are as shown in
Table 4.1.
Dimensional item symbols used in the accuracy
standard are given in Table 4.2, the radial bearing
accuracy specified every accuracy class given in Table
4.3, the thrust bearing accuracy specified every accuracy
class given in Table 4.4, and the allowable values for
chamfering dimension given in Table 4.5.
Table 4.2 Dimensional item symbols used in applicable standards
Classification Symbols
Dimensional
accuracy
Profile
accuracy
Running
accuracy
dmp
ds
Dmp
Ds
Bs
Cs
Vdp
Vdmp
VDp
VDmp
VBs
VCs
Kia
Kea
Sia
Sea
Sd
SD
Symbol representation
Dimensional tolerance for in-plane
mean bore diameter
Dimensional tolerance for bore diameter
Dimensional tolerance for in-plane
mean outer diameter
Symbols under
JIS B 0021 (Reference)
Dimensional tolerance for outer diameter
Dimensional tolerance for inner ring width
Dimensional tolerance for outer ring width
Variation of in-plane bore diameter Roundness
Variation of in-plane mean bore diameter Cylindricality
Variation of in-plane outer diameter Roundness
Variation of in-plane mean outer diameter Cylindricality
Variation of inner ring width Parallelism
Variation of outer ring width Parallelism
Radial run-out of inner ring Run-out
Radial run-out of outer ring Run-out
Axial run-out of inner ring
Axial run-out of outer ring
Lateral run-out (inner ring) Run-out
Outer diameter run-out (outer ring) Run-out
1) The roundness specified in JIS B 0021 is applicable to the tolerance Vdp for
variation of radial in-plane bore diameter or nearly half of VDp.
2) The cylindricality specified in JIS B 0021 is applicable to the tolerance Vdmp
for in-uniformity of radial in-plane mean diameter or nearly half of VDmp.
1
2
1
2
Table 4.1 Bearing types and corresponding accuracy classes
Bearing type Applicable accuracy class Applicable table
Needle roller bearing,
Clearance-adjustable needle roller bearing
JIS Class-0
JIS Class-6
JIS Class-5
JIS class-4
JIS class-4
Table 4.3
Table 4.3
Complex bearing
Radial bearing
Thrust bearing
JIS Class-0
NTN Class 0
JIS Class-6
NTN Class 6
JIS Class-5
NTN Class 5
NTN Class 4
Table 4.3
Table 4.4
Needle roller bearing
with double-direction
thrust roller bearing
Radial bearing
Thrust bearing
JIS Class-5
NTN Class 5
JIS Class-4
NTN Class 4
Table 4.3
Table 4.4
Thrust roller bearing
Roller follower/cam follower
NTN Class 0
JIS Class-0
NTN Class 6
NTN Class 5
NTN Class 4
Table 4.4
Table 4.3
A-25