>> P.47
A44ABCDEFGHIJKLMDesignofShaftandHousingAccuracyandroughnessofshaftandhousingAccuracyandroughnessoffittingsurfaceSincethebearingringsofneedlerollerbearingsarethin,theirperformanceiseasilyaffectedbypooraccuracyofshaftsorhousings.Undergeneraloper-atingconditions,thefittingsurfacesofshaftsandhousingscanbefinishedbylatheturning.However,whentheloadisgreatandhighaccuracyandlownoisearerequired,agrindingfinishisrequired.Table26showstheaccuracyandroughnessoffittingsurfacesforgeneraluse.AccuracyandroughnessofracewaysurfaceIncaseofneedlerollerbearingsunlikeotherbear-ings,matingsurfacessuchasshaftandhousingboresurfacescanbeuseddirectlyastheracewaysur-faces.Forsuchuse,accuracyandroughnessoftheracewaysurfacesareimportantbecausetheywillinfluencebearinglife,noiseandaccuracy.Ingeneral,accuracyandroughnessofracewaysur-facesarebasedonTable26.InclinationofshaftShaftsandouterringsmayhavesomeinclinationbetweenthemduetodeflectionoftheshaft,machin-ingaccuracyofshaftsandhousings,errorsinmount-ing,etc.Inthiscase,theuseoftwoormorebearingsintan-demarrangementonasingleshaftshouldbeavoided.Instead,abearingwithlargeloadratingsshouldbeused.Itisrecommendedthatinclinationofshaftsbelessthan1/1000.Table27ToleranceclassITvaluesforbasicdimensionsBasicdimensionmmOverIncl.Toleranceclass(1)IT5ToleranceμmIT6IT7-3610183050801201802503154005003610183050801201802503154005006304568911131518202325273068911131619222529323640441012151821253035404652576370Table26SpecificationsofshaftsandhousingsforradialneedlerollerbearingsItemShaftFittingsurfaceRacewaysurfaceRacewaysurfaceFittingsurfaceHousingboreCircularity0.3×IT6(1)or0.3×IT5(1)0.5×IT6(2)or0.5×IT5(2)0.8(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)CylindricitySurfaceroughnessμmRa(μmRy)HardnessNotes(1)30%orlessofthedimensionaltoleranceforshaftsorhousingboresisrecommended.(2)50%orlessofthedimensionaltoleranceforshaftsorhousingboresisrecommended.(3)Whenrequiredaccuracyisnotcritical,asurfaceroughnesswithin0.8μmRa(3.2μmRy)isallowable.(4)Anappropriatethicknessofthehardenedlayerisrequired.RemarkFortoleranceclassIT,seeTable27.Note(1)BasedonJISB0401.1N=0.102kgf=0.2248lbs.1mm=0.03937inch
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