VW01129-EN-2007-01-01

Klass.-Nr./Class.No.01712January2007LimitValuesforCoefficientsofFrictionMechanicalJoiningElementswithMetricISOThreadVW01129KonzernnormDescriptors:coefficientsoffriction,limitvalues,mechanicaljoiningelements,metricISOthreadsPage1of4Normung/Standards(E2TC,1733)Werthe2-NQ-K/4Tel.:[phone]KühnTel:[phone]TerlindenConfidential.Allrightsreserved.NopartofthisdocumentmaybetransmittedorreproducedwithoutpriorpermissionofaStandardsDepartmentoftheVolkswagenGroup.PartiestoacontractcanonlyobtainthisstandardviatheB2Bsupplierplatform“”.VOLKSWAGENAGNormvorAnwendungaufAktualitätprüfen/Checkstandardforcurrentissuepriortousage.FormFE41-09.06ContentsPage1Scope..................................................................................................................................12Coefficientsoffriction..........................................................................................................12.1Totalcoefficientoffriction...................................................................................................22.2Threadandheadcoefficientsoffriction..............................................................................23Test.....................................................................................................................................33.1Firstsampling,standard-productionmonitoring..................................................................33.2Releaseofnewsurfacecoatings,problemanalyses..........................................................33.3Evaluationofthecoefficient-of-frictiontest..........................................................................33.4Testoflooseningatelevatedtemperature..........................................................................44Terms..................................................................................................................................45Referencedstandards.........................................................................................................4ChangesThefollowingchangeshavebeenmadeascomparedtoVolkswagenstandardVW01129,2001-05:─StandardcompletelyrevisedPreviousissues2001-051ScopeThisstandardappliestomechanicaljoiningelementswithmetricISOthreadandflatheadbearingsurface.2CoefficientsoffrictionCoefficientoffriction,tighteningtorqueandpreloadforceinteractwitheachother(seeVW01126-1andVW01126-2).Thecoefficientoffrictionisaffectedbythematerialcombinationandthesurfaceprotectiontype.Inordertoachieveauniformthreadingofjoints,thevariationrangeofthepermissiblefrictioncoefficientmustberestrictedandthepositionofthemeanvaluemustbedesignated.Suitablelubrication(integratedinthesurfaceprotectivecoatingorsubsequentlyapplied)canmeetthesespecifications(seeVW01110andVW13750).Thecoefficientsoffrictiondeterminedmaydeviatefromthecoefficientsoffrictionwhichariseinactualapplicationduetovariousmarginalconditions.Inthecaseofspecialdesignparts,wherethedeterminationofthecoefficientoffrictionisnotpossible,post-treatmentmustbecarriedoutinsuchamannerthatcorrespondingpartswithoutspecialdesignwouldachievethisvalue.TheEnglishtranslationisbelievedtobeaccurate.IncaseofdiscrepanciestheGermanversionshallgovern.NumericalnotationaccordingtoISOpractice(seeVW01000).Page2VW01129:2007-01Asthecoefficientsoffrictionareinfluencedbythetighteningspeed,themeasurementsshallbeperformedunderequalconditions.Forthispurpose,two-stagetighteningatatighteningspeedof200min-1aswellasfinaltighteningat20min-1areprescribedforthecoefficient-of-frictionmeasurement.ForfurtherspecificationsseeVW01131.2.1TotalcoefficientoffrictionThetotalcoefficientoffrictionµtotisdeterminedbythecoefficientsoffrictioninthescrewthreadandbelowthescrewheadornutbearingsurface.Thepermissibletolerancesapplytoboththetotalcoefficientoffrictionaswellastheindividualcoefficientsoffrictionofthescrewheadornutbearingsurfaceµbandthecoefficientoffrictioninthescrewthreadµth.Itisdefinedasfollows:0,09≤µ≤0,15Withamaximumpermissiblemeasuringuncertaintyof∆µ=0,01,thisresultsinthefollowingrangeofcoefficientsoffrictionwhichistotobeagreeduponseparatelyasacceptancerequirement:0,08≤µ≤0,16(SeealsoDINENISO14253-1andVDASheet235-101).Ameanvalueofthemeasurementseriesofµtot=0,12isdesirable.Thetotalcoefficientoffrictionisdefinedasfollows:btotDdPFT5,0577,022+−=πµHere,thefollowingshallapplytoaplane,ring-shapedbearingsurface:20hbdDD+=2.2ThreadandheadcoefficientsoffrictionThethreadcoefficientsoffrictionaredefinedasfollows:2577,02dPFTththπµ−=2577,02dPFTthlthlπµ+=fortighteningforlooseningThecoefficientsoffrictionofthenutandscrew-headbearingsurfacearedefinedasfollows:FDTbbb×=5,0µPage3VW01126:2007-01NOTE1:Higherthreadcoefficientsoffrictioncausealessefficientscrewutilizationduetotheincreaseinthecomparisonstress;thisresultsinalowerpreloadforcealsointhecaseofscrewassemblybeyondtheelasticlimit.NOTE2:Fallingbelowthethreadcoefficientoffrictionofµth=0,08resultsinareducedself-lockingcapability.Asanexample:µth=0,06forM6screwsresultsinacompletelossoftheself-lockingcapabilityinthet