Page 196 - needle bearings
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Clearance-adjustable needle roller bearings
NTN
Clearance-Adjustable Needle Roller Bearings
This bearing type comprises a solid outer ring with The radial clearance is fine-adjustable by an load to be
special machined section and needle rollers and cage applied to the bearing in axial direction, that is, axial
built in the outer ring. The outer ring, needle rollers and shrinkage of the outer ring. This bearing type is mainly
cage are inseparable from each other. The raceway applied to the work spindle of a machine tool etc. which
diameter of the outer ring is shrunk and the roller require high running accuracy, whose accuracy class is
inscribed circle diameter (Fw) is reduced correspondingly JIS Class-4.
by pressing the outer ring in axial direction.
Applied shaft Composition of
Bearing type diameter (mm) nominal bearing number Remarks
Type RNA49ʝS
RNA 49 05 S
П30ʙП125
Type code The dimensional accuracy, profile
Dimension series accuracy and running accuracy
Bore diameter number conform to JIS Class-4 so as to be
available for applications requiring
Tail code
high running accuracy.
Type NA49ʝS
Another inner ring type with
grinding allowance for its raceway
surface can also be supplied upon
[Tail code] request.
П25ʙП110 S: Clearance-adjustable type
Bearing accuracy Table 1 Bearing fit in shaft and housing
Application of this bearing type is limited to the portions Bearing type Shaft Housing
of a machine which require high running accuracy.
RNA49ʝS m5
Therefore, the dimensional accuracy, profile accuracy K4
NA49ʝS k5
and running accuracy of this bearing type conform to JIS
Class-4. Higher running accuracy can be achieved by
finishing the inner ring raceway surface with grinding
allowance by grinding, after the inner ring was press-fitted Shaft and housing accuracy
on a shaft. Feel free to contact NTN for the more detailed
This bearing type which is applied to the portions of a
information.
machine requiring high running accuracy is clamped with
the outer ring inclination in installing restrained as less as
Radial clearance and bearing fits possible. Therefore, the profile accuracy of the shaft and
the housing must be made higher than that for general
The Type NA49ŋŋŋŋS with inner ring has a radial
clearance smaller than the specific ordinary clearance, machined ring needle roller bearings. (Table 2)
while the radial clearance of Type RNA49ŋŋŋŋS without
inner ring is determined by shaft diameter being selected Table 2 Shaft and housing accuracy
per applicable "Dimensions Table" which specifies the
dimensional tolerances for the roller inscribed circle Characteristics Shaft Housing
diameter (Fw). Roundness (max) IT2 IT3
The outer ring must be fitted in a housing by "close fit"
Cylindricality (max) IT2 IT3
or "tight fit" (interference of approximately 5Жm) to shrink
the raceway diameter by pressing the outer ring in axial Shoulder perpendicularity (max) IT3 IT3
direction.
Bearing fit on a shaft and in a housing shall be per
Table 1.
B-134