Page 29 - needle bearings

Bearing Accuracy
NTN

4. Bearing Accuracy

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

Table 4.1 Bearing types and corresponding accuracy classes

Bearing type Applicable accuracy class Applicable table
Needle roller bearing, JIS Class-0 JIS Class-6 JIS Class-5 JIS class-4 Table 4.3
Clearance-adjustable needle roller bearing ʕ ʕ ʕ JIS class-4 Table 4.3
Radial bearing JIS Class-0 JIS Class-6 JIS Class-5 ʕ Table 4.3
Complex bearing
Thrust bearing NTN Class 0 NTN Class 6 NTN Class 5 NTN Class 4 Table 4.4
Needle roller bearing Radial bearing ʕ ʕ JIS Class-5 JIS Class-4 Table 4.3
with double-direction
thrust roller bearing Thrust bearing ʕ ʕ NTN Class 5 NTN Class 4 Table 4.4
Thrust roller bearing NTN Class 0 NTN Class 6 NTN Class 5 NTN Class 4 Table 4.4
Roller follower/cam follower JIS Class-0 ʕ ʕ ʕ Table 4.3

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