Page 196 - needle bearings
P. 196

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.


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