>> P.47
1N=0.102kgf=0.2248lbs.1mm=0.03937inchABCDEFGHIJKLMShafts and outer rings may have some inclination between them due to deection of the shaft, machin-ing accuracy of shafts and housings, errors in mount-ing, etc.In this case, the use of two or more bearings in tan-dem arrangement on a single shaft should be avoided. Instead, a bearing with large load ratings should be used.It is recommended that inclination of shafts be less than 1/1000.Table 27 Tolerance class IT values for basic dimensionsBasic dimensionTolerance class(1)mmIT5IT6IT710121518212530354046525763706891113161922252932364044Toleranceμm45689111315182023252730361018305080Incl.120180250315400500630Over-361018305080120180250315400500Note(1)Based on JIS B 0401.Accuracy and roughness of shaft and housingAccuracy and roughness of fitting surfaceSince the bearing rings of needle roller bearings are thin, their performance is easily affected by poor accuracy of shafts or housings. Under general oper-ating conditions, the fitting surfaces of shafts and housings can be nished by lathe turning. However, when the load is great and high accuracy and low noise are required, a grinding nish is required.Table 26 shows the accuracy and roughness of tting surfaces for general use.Accuracy and roughness of raceway surfaceIn case of needle roller bearings unlike other bear-ings, mating surfaces such as shaft and housing bore surfaces can be used directly as the raceway sur-faces. For such use, accuracy and roughness of the raceway surfaces are important because they will inuence bearing life, noise and accuracy.In general, accuracy and roughness of raceway sur-faces are based on Table 26.Design of Shaft and HousingInclination of shaftTable 26 Specifications of shafts and housings for radial needle roller bearingsShaftHousing boreFitting surfaceRaceway surfaceFitting surfaceRaceway surfaceItemCircularityCylindricity0.3×IT6(1)or0.3×IT5(1)0.5×IT6(2)or0.5×IT5(2)Surface roughnessμmRa(μmRy)Hardness0.8(3.2)-0.3×IT6(1)or0.3×IT5(1)0.3×IT6(1)or0.3×IT5(1)0.2(3)(0.8)58〜64HRC(4)0.3×IT7(1)or0.3×IT6(1)0.5×IT7(2)or0.5×IT6(2)1.6(6.3)-0.3×IT7(1)or0.3×IT6(1)0.3×IT7(1)or0.3×IT6(1)0.2(3)(0.8)58〜64HRC(4)Notes(1)30% or less of the dimensional tolerance for shafts or housing bores is recommended.(2)50% or less of the dimensional tolerance for shafts or housing bores is recommended.(3)When required accuracy is not critical, a surface roughness within 0.8 μmRa (3.2 μmRy ) is allowable.(4)An appropriate thickness of the hardened layer is required.Remark For tolerance class IT, see Table 27.A44
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