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AS+1275-1985

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AS1275—1985

AustralianStandard®

METRICSCREWTHREADSFORFASTENERS

ThisAustralianstandardwaspreparedbyCommitteeME/28,ScrewThreads.ItwasapprovedonbehalfoftheCounciloftheStandardsAssociationofAustraliaon8November1984andpublishedon4April1985.

ThefollowinginterestsarerepresentedonCommitteeME/28:

ConfederationofAustralianIndustryCSIRO,DivisionofAppliedPhysicsDepartmentofDefenceDepartmentofDefenceSupport

DepartmentofTechnicalandFurtherEducation,N.S.W.ElectricitySupplyAssociationofAustraliaFastenersInstituteofAustralia

FederalChamberofAutomotiveIndustriesInstitutionofEngineersAustraliaInstitutionofProductionEngineers

MetalTradesIndustryAssociationofAustraliaRailwaysofAustraliaCommittee

SocietyofAutomotiveEngineers,Australasia

ReviewofAustralianStandards.Tokeepabreastofprogressinindustry,AustralianStandardsaresubjecttoperiodicreviewandarekeptuptodatebytheissueofamendmentsorneweditionsasnecessary.ItisimportantthereforethatStandardsusersensurethattheyareinpossessionofthelatestedition,andanyamendmentsthereto.

FulldetailsofallAustralianStandardsandrelatedpublicationswillbefoundintheStandardsAustraliaCatalogueofPublications;thisinformationissupplementedeachmonthbythemagazine‘TheAustralianStandard’,whichsubscribingmembersreceive,andwhichgivesdetailsofnewpublications,neweditionsandamendments,andofwithdrawnStandards.

SuggestionsforimprovementstoAustralianStandards,addressedtotheheadofficeofStandardsAustralia,arewelcomed.NotificationofanyinaccuracyorambiguityfoundinanAustralianStandardshouldbemadewithoutdelayinorderthatthemattermaybeinvestigatedandappropriateactiontaken.

ThisStandardwasissuedindraftformforcommentasDR83215.

AS1275—1985

AustralianStandard®

METRICSCREWTHREADSFORFASTENERS

Firstpublished(asASB275)..............1968AS1275firstpublished..................1972Secondedition........................1985Incorporating:Amdt1—1986

PUBLISHEDBYSTANDARDSAUSTRALIA

(STANDARDSASSOCIATIONOFAUSTRALIA)1THECRESCENT,HOMEBUSH,NSW2140

ISBN0726236284

AS1275—19852

PREFACE

ThiseditionofthisstandardwaspreparedbytheAssociation’sCommitteeonScrewThreads,tosupersedeAS1275—1972.

SinceAS1275wasfirstpublished,themajorISOstandardsdealingwithmetricscrewthreads(seelaterlisting)havebeenrevised,andarenowinconflictwiththeinformationgiveninAS1275—1972.Thisisparticularlytruewithrespecttotherootcurvatureforexternalthreads,andthelimitsspecifiedforthethreadrootsofbothexternalandinternalthreads.

AfurtherimportantconsiderationisthattheISOstandardsformetricscrewthreadsarenowbeingadoptedvirtuallyunchangedbymostdevelopedanddevelopingcountries,andthereforeitisimportantthattheAustralianstandardsbealignedwiththeirISOcounterpartsasmuchaspossible.Thishasbeentheaiminthiseditionofthestandard.

DuringthepreparationofAS1275intheearly1970s,itwasnotedbythecommitteethattheISOsymbolsusedforthevariousscrewthreadparameterswereillogical,andsoamorelogicalsystemwasintroducedintheAustralianstandards.ThiswassupportedbysustainedcommenttoISO/TC1proposingtheAustraliansymbols.UnfortunatelytheAustralianproposalswerenotacceptedbyISO/TC1andtheoriginalISOsymbolswereretained.OneofthemajorchangesinthiseditionthereforehasbeentointroducetheISOsymbologyforthescrewthreadparameters.

Theothermajorchangeiswithregardtothelimitsgivenforthethreadrootsonbothexternalandinternalthreads.InAS1275—1972theselimitswerecompletelyspecified,whereasintheISOstandardsonlytheminimumminordiameterisspecifiedforexternalthreadsandthenominal(basic)majordiameterisgivenforinternalthreads;theactuallimitsbeingindirectlycontrolledbythelengthofstraightflanks.FurthermorearootcurvatureforexternalthreadsisonlyspecifiedforthreadsintendedforfastenersofpropertyClass8.8andabove.Allotherexternalthreadsmayhavearootconfigurationinaccordancewiththebasic/designprofile.

ItwasconsideredthattheISOapproachonthelimitsforthethreadrootswaspracticalandshouldbeadopted,becausethiswouldpermitmaximumflexibilityinmanufacturewithoutbeingundulydetrimentaltoeitherthestrengthofthescrewthreadortoitsassemblyproperties.However,theISOrootcurvatureforexternalthreads,takentotheextremecouldcauseproblemsbyintroducinganotcheffect,whichmayleadtofatiguefailureinthreadsinsomesteelswhichhaveahightensileleveland/orhavebeenseverelycoldworked.Acautionarystatementtothiseffecthasthereforebeenincludedinthisstandard.

ThisstandardhasbeenbasedonandisincompletealignmentwiththefollowingISOstandards:ISO68—1973ISOGeneralPurposeScrewThreads—BasicProfileISO261—1973ISOGeneralPurposeMetricScrewThreads—GeneralPlanISO262—1973ISOGeneralPurposeMetricScrewThreads—SelectedSizesforScrews,Bolts

andNuts

ISO724—1978ISOMetricScrewThreads—BasicDimensions

ISO965/1—1980ISOGeneralPurposeMetricScrewThreads—Tolerances—

Part1:PrinciplesandBasicData

ISO965/2—1980ISOGeneralPurposeMetricScrewThreads—Tolerances—

Part2:LimitsofSizesforGeneralPurposeBoltandNutThreads—MediumQuality

ISO965/3—1980ISOGeneralPurposeMetricScrewThreads—Tolerances—

Part3:DeviationsforConstructionalThreads

STANDARDSAUSTRALIA

UsersofStandardsareremindedthatcopyrightsubsistsinallStandardsAustraliapublicationsandsoftware.ExceptwheretheCopyrightActallowsandexceptwhereprovidedforbelownopublicationsorsoftwareproducedbyStandardsAustraliamaybereproduced,storedinaretrievalsysteminanyformortransmittedbyanymeanswithoutpriorpermissioninwritingfromStandardsAustralia.Permissionmaybeconditionalonanappropriateroyaltypayment.RequestsforpermissionandinformationoncommercialsoftwareroyaltiesshouldbedirectedtotheheadofficeofStandardsAustralia.

StandardsAustraliawillpermitupto10percentofthetechnicalcontentpagesofaStandardtobecopiedforuseexclusivelyin-housebypurchasersoftheStandardwithoutpaymentofaroyaltyoradvicetoStandardsAustralia.

StandardsAustraliawillalsopermittheinclusionofitscopyrightmaterialincomputersoftwareprogramsfornoroyaltypaymentprovidedsuchprogramsareusedexclusivelyin-housebythecreatorsoftheprograms.

CareshouldbetakentoensurethatmaterialusedisfromthecurrenteditionoftheStandardandthatitisupdatedwhenevertheStandardisamendedorrevised.ThenumberanddateoftheStandardshouldthereforebeclearlyidentified.

Theuseofmaterialinprintformorincomputersoftwareprogramstobeusedcommercially,withorwithoutpayment,orincommercialcontractsissubjecttothepaymentofaroyalty.ThispolicymaybevariedbyStandardsAustraliaatanytime.

©Copyright

3AS1275—1985

CONTENTS

Page

SECTION1.SCOPEANDGENERAL

1.1Scope............................................1.2Application........................................1.3ReferencedDocuments...............................1.4Definitions........................................1.5Symbols..........................................1.6Verification.......................................1.7

StressArea(As)........

.....

.................

SECTION2.SCREWTHREADPROFILES

2.1ScopeofSection....................................2.2BasicProfile.......................................2.3MaximumMaterialProfile.............................2.4LeastMaterialProfile................................2.5LimitingProfiles....................................2.6

RootContours.........

.....

.......................

SECTION3.DIMENSIONSANDTOLERANCES

3.1ScopeofSection...................................3.2BasicDimensions..................................3.3TolerancePositions.................................3.4FundamentalDeviations..............................3.5ToleranceGrades..................................3.6ToleranceClasses..................................3.7LimitsofSize.....................................3.8CoatedThreads...................

.................SECTION4.DESIGNATIONOFSCREWTHREADS

4.1ScopeofSection...................................4.2CompleteDesignationforInternalThreads................4.3CompleteDesignationforExternalThreads................4.4ShortenedDesignationforCoarsePitchSeriesThreads........4.5DesignationofaThreadFit....................

.......APPENDICESANotesontheProductionofExternalThreads...............BComparisonofSymbols(Notations)forScrewThreadParameters

4444444

556778

1010101011111414

1515151515

AS1275—19854

STANDARDSASSOCIATIONOFAUSTRALIA

AustralianStandard

for

METRICSCREWTHREADSFORFASTENERS

SECTION1.SCOPEANDGENERAL

1.1SCOPE.Thisstandardspecifiesrequirementsforsinglestart,parallel,coarsepitchseriesmetricscrewthreads,mainlyintendedforthreadedfasteners.Thestandardcoversscrewthreadsfrom1.6mmdiameteruptoandincluding64mmdiameter,intoleranceclasses6e,6f,6gand8g,forexternalthreads;and6Hand6Gforinternalthreads.

Thestandardgivesinformationonsymbolsforscrewthreadparameters,tolerances,deviations,threadclasses,designationandverification.

Appendicesareincludedgivingnotesontheproductionofscrewthreadsandacomparisonofsymbolsusedinthisstandardandthe1972edition.

NOTES:

1.Thecoarsepitchseriesgiveninthisstandardcomprisesthe1stand2ndchoicediameter/pitchcombinations(forcoarsepitchseriesthreads)extractedfromAS1721.TheyarethesameasthosegiveninISO261andISO262;thelattercoveringdiametersuptoandincluding39mmonly.

2.Forinformationonthebasesofthemetricscrewthreadsystemandassociatedformulas,seeAS1721.

ISO262

ISOGeneralPurposeMetricScrewThreads—SelectedSizesforScrews,BoltsandNuts

1.4DEFINITIONS.Forthepurposeofthisstandard,thedefinitionsgiveninASXXXXapply.

1.5SYMBOLS.ThesymbolsusedinthisstandardtodefinethescrewthreadparametersaregiveninTable1.1.

NOTE:ThesearenowalignedwiththeISOsymbols.ForcomparisonofthecurrentsymbolswiththoseusedinAS1275—1972,seeAppendixB.

TABLE1.1SYMBOLS

SymbolDD1D2dd1d2PHRSNLTTD1TD2TdTd2G,He,f,gAs

basicbasicbasicbasicbasicbasicpitch

heightoffundamentaltrianglerootradiusofexternalthread

designationforlengthsofthreadengagementgroupShort

designationforlengthsofthreadengagementgroupNormal

designationforlengthsofthreadengagementgroupLongtolerance

toleranceonminordiameterofinternalthreadtoleranceonpitchdiameterofexternalthreadtoleranceonmajordiameterofexternalthreadtoleranceonpitchdiameterofexternalthreadfundamentaldeviationsforinternalthreadsfundamentaldeviationsforexternalthreadsnominalstressarea(externalthreads)

Explanation

majordiameterofinternalthreadminordiameterofinternalthreadpitchdiameterofinternalthreadmajordiameterofexternalthreadminordiameterofexternalthreadpitchdiameterofexternalthread

1.2APPLICATION.Thisstandardgivesinformationonthedesign,manufactureanduseofISOcoarsepitchseriesmetricparallelscrewthreads.Thestandardisintendedforadoptionbyindustryandgovernmentauthoritiesconcernedwiththedesign,manufactureand/oruseofmetricscrewthreads.1.3REFERENCEDDOCUMENTS.Thefollowingstandardsarereferredtointhisstandard:AS1014GaugingofMetricScrewThreadsAS1098Roller-typeScrewCalliperGaugesAS1110ISOMetricHexagonPrecisionBoltsand

Screws

AS1111ISOMetricHexagonCommercialBolts

andScrews

AS1112ISOMetricHexagonNuts,including

ThinNuts,SlottedNutsandCastleNuts

AS1214Hot-dipGalvanizedCoatingson

ThreadedFasteners(ISOMetricCoarseThreadSeries)

AS1252High-strengthSteelBoltswith

AssociatedNutsandWashersforStructuralEngineering

AS1654LimitsandFitsforEngineeringAS1721GeneralPurposeMetricScrewThreadsAS1897ElectroplatedCoatingsonThreaded

Components(MetricCoarseSeries)

ASXXXX*GlossaryofTermsforScrewThreadsISO261ISOGeneralPurposeMetricScrew

Threads—GeneralPlan

1.6VERIFICATION.TheformanddimensionsofscrewthreadstothisstandardshouldpreferablybeverifiedbygauginginaccordancewithAS1014.

Themethod(s)ofverification(inspection)tobeusedonanyparticularoccasionwillhowever,dependonsuchthingsasthethreaddiameter,thethreadclass,thenumberofitemsproducedandthemethodofmanufacture.

Wheregaugingisimpractical,thethreadsmaybeverifiedbydirectmeasurementorbyopticalmethods;oracombinationofboth.

1.7STRESSAREA(As).Thecross-sectionalareausedforcalculatingthetensileandproofloadsforthreadedfastenersisbasedonthefollowingformula:

NOTE:CalculatedvaluesofthestressareasaregiveninTable3.3.*Incourseofpreparation.

5AS1275—1985

SECTION2.SCREWTHREADPROFILES

2.1SCOPEOFSECTION.ThisSectionspecifiesthebasicprofile,themaximummaterialprofilesandthelimitingprofilesforexternalandinternalmetricscrewthreads.Thesectionalsoincludesinformationandvaluesofthemainelementsusedtoderivethe

basicandlimitingthreadprofiles.

2.2BASICPROFILE.ThebasicprofileofISOgeneralpurposemetricscrewthreadsisshowninFig.2.1.ThedimensionsforthevariouspitchesaregiveninTable2.1.

NOTE:Forexplanationofsymbols,seeTable1.1.

Fig.2.1.ISOBASICPROFILE

TABLE2.1

DIMENSIONSOFTHEBASICPROFILE

millimetres

PitchP0.350.40.450.50.60.70.750.811.251.51.7522.533.544.555.56

H0.3030.3460.3890.4330.5190.6060.6490.6920.8661.0821.2991.5151.7322.1652.5983.0313.4643.8974.3304.7635.196

109410711013615218519820025532038544051063076089102114127140152

/H443506570633760886949013266582899215532165798431063696329962595

/H666904142380856332570808760949139329519899279658038418798177557

H/40.0750.0860.0970.1080.1290.1510.1620.1730.2160.2700.3240.3780.4330.5410.6490.7570.8660.9741.0821.1901.299

777603428253904554380205506633760886013266519772025279532785038

H/80.0370.0430.0480.0540.0640.0750.0810.0860.1080.1350.1620.1890.2160.2700.3240.3780.4330.4870.5410.5950.649

889301714127952777190603253316380443506633760886013139266392519

0.1890.2160.2430.2700.3240.3780.4050.4330.5410.6760.8110.9471.0821.3531.6231.8942.1652.4352.7062.9763.2470.1130.1290.1460.1620.1940.2270.2430.2590.3240.4050.4870.5680.6490.8110.9741.1361.2991.4611.6231.7861.948

AS1275—19856

2.3MAXIMUMMATERIALPROFILE.

2.3.1Maximummaterialprofile—internalthread.TheprofileofanexternalscrewthreadatitsmaximummaterialconditionisshowninFig.2.2.Itisthesameasthebasicprofileexceptthatinpractice,therootisroundedasshownbythedottedline,andclearedbeyondawidthP/8.

2.3.2Maximummaterialprofile—externalthread.TheprofileofanexternalscrewthreadatitsmaximummaterialconditionisshowninFig.2.3.Itisthesameasthebasicprofile,exceptthat—

(a)inpracticethecrestsmayberoundedinsidethe

maximumprofileasshownbythedottedline;and(b)thethreadroots(minordiameter)mayrequiretobe

modifiedinaccordancewithClause2.6.2.

Fig.2.2.MAXIMUMMATERIALPROFILEOFANINTERNALTHREAD

NOTES:1.Fordetailsofrootcurvature,seeClause2.6.2andFig.2.7.2.Theactualformofanyroundingofthecrestsorrootsofthethreadwillnotbedetectedby

conventionalgaugingsincesuchgaugesareclearedatthecrestandrootandonlyassessthestraightflanksovertheheightofthebasicprofile,i.e.5/8Hradialdepth.3.Ifassessmentoftherootcurvatureisrequired,verificationbyopticalprojectionisnecessaryandit

istobestatedinthedesignrequirements.

Fig.2.3.MAXIMUMMATERIALPROFILEOFANEXTERNALTHREAD

7AS1275—1985

2.4LEASTMATERIALPROFILE.TheleastmaterialprofileofbothinternalandexternalthreadsisderivedfromthemaximummaterialprofileusingtheinformationgiveninSection3.2.5LIMITINGPROFILES.

2.5.1Limitingprofiles—internalthreads.Typical

limitingprofilesforinternalscrewthreads,involvingtolerancepositionsHandG,areshowninFigs2.4and2.5respectively.

2.5.2Limitingprofiles—externalthreads.Typicallimitingprofilesforexternalscrewthreads,involvingtolerancepositionse,fandg,areshowninFig.2.6.

Fig.2.4.LIMITINGPROFILESFORINTERNALTHREADS—TOLERANCEPOSITIONH

Fig.2.5.LIMITINGPROFILESFORINTERNALTHREADS—TOLERANCEPOSITIONG

AS1275—19858

Fig.2.6.LIMITINGPROFILESFOREXTERNALTHREADS—

TOLERANCEPOSITIONSe,fANDg

2.6ROOTCONTOURS.

2.6.1Internalthreads.Theactualrootcontourshallnotatanypointtransgressthebasicprofile.InpracticethetapsusedtoproduceinternalthreadswillnormallyproducearoundedthreadrootclearedbeyondawidthofP/8asshowninFig.2.2.

2.6.2Externalthreads.Theactualrootcontourshallnotatanypointtransgressthebasicprofile.Howeveritisrecommendedthattherootprofileshouldnotbeflat,withsharpcorners,butshouldbesmoothlyrounded.

ForthreadsonfastenersofpropertyClass8.8andhigher(seeAS1110andAS1252)andsimilarmaterialswithsimilarproperties,therootprofileshallhaveanon-reversingcurvature,noportionofwhichshallhavearadiuslessthanRmin,whichistangentialtothethreadflank.TherootprofilemaybecomprisedofarcsofminimumradiusRmintowhichtheflanksandaflatattherootaretangential(seeFig.2.7).ThevaluesofRminaregiveninTable2.2.Themaximumtruncationis—

andtheminimumtruncationis—0.125P≈

Theaboveprincipleisrecommendedforallotherexternalthreads,particularlythoseusedinapplicationssubjecttofatigueorimpact.

ExternalthreadsmustbeacceptedbyaGOscrewringorGOscrewcallipergauge.

Itisnotpracticaltospecifylimitsfortheminordiameterofanexternalthread.Aminimumminordiametercanbederivedwhentheblendradiusequals0.125P,andtheflanksareattheleastmaterialcondition,butastheflanksapproachthemaximummaterialconditionthemaximumminordiameterwilltendtoreduce,andthelimitingvaluesaredependentontheactualcrestdiameterandpitchdiameterofthegaugeaswellasthesubjectscrewthread(seeFig.2.7).

AsnotedinFig.2.3,conventionalgaugingwillnotexaminetherootcontoursanditisrecommendedthatgaugingbesupplementedbyprofileprojectionoftheexternalthreadroot.

9AS1275—1985

(a)Tolerancepositionh(b)Tolerancepositionse,fandg

Fig.2.7.ROOTCONTOURSFORBOLTTHREADS

(PROPERTYCLASS8.8ANDHIGHER)

TABLE2.2.

MINIMUMROOTRADII

millimetres

PitchP0.20.250.30.350.40.450.50.60.70.750.811.251.51.7522.533.544.555.56

NOTE:Rmin=0.125P.

Rmin0.0250.0310.0380.0440.0500.0560.0630.0750.0880.0940.1000.1250.1560.1880.2190.2500.3130.3750.4380.5000.5630.6250.6880.750

AS1275—198510

SECTION3.DIMENSIONSANDTOLERANCES

3.1SCOPEOFSECTION.ThisSectionsetsoutthebasicdimensionsandthreadtolerancesystem,andgivesinformationonthetolerancegrades,fundamentaldeviations,andtoleranceclassesusedforISOmetriccoarsepitchseriesthreads.

TheSectionalsogivesinformationonlengthsofthreadengagementapplicabletothetoleranceclassesgiveninthestandard.

NOTE:Forfurtherinformationondeviationsandtolerancesandtheirdeviation,seeAS1721.

Basicminordiameter

d1=d-2×5/8H=D-1.0825P3.3TOLERANCEPOSITIONS.Thefollowingtolerancepositionsaregiveninthisstandard:(a)Forinternalthreads:

Gwithapositivefundamentaldeviation.Hwithzerofundamentaldeviation.SeeFigs2.4and2.5.(b)Forexternalthreads:

e,fandgwithanegativefundamentaldeviation.3.4FUNDAMENTALDEVIATIONS.3.4.1General.Fundamentaldeviationsaredesignatedbyuppercaselettersforinternal(nut)threads,andlowercaselettersforexternal(bolt)threads.Thefundamentaldeviationsforinternalthreadsandforexternalthreads,arepositionedwithrespecttothebasicsizeasshowninFig.3.1.Forexplanationofsymbols,seeTable1.1.

3.2BASICDIMENSIONS.ValuesforthebasicpitchdiametersandminordiametersaregiveninTable3.1.Thevaluesroundedtothethirddecimalplacehavebeencalculatedfromthefollowingformulas:Basicpitchdiameter

D=D-2×3/8H=D-0.6495P

Basicpitchdiameter

d2=d-2×3/8H=D-0.6495P

Basicminordiameter

D1=D-2×5/8H=D-1.0825P

Fig.3.1.SCREWTHREADDEVIATIONS

TABLE3.1

BASICDIMENSIONS

millimetres

Basicmajordia.FirstSecondchoicechoice1.6

1.8

2.2

2.53

3.5

4.5

PitchP0.350.350.40.450.450.50.60.70.750.81

Basicpitchdia.1.3731.5731.7401.9082.2082.6753.1103.5454.0134.4805.350

BasicBasicmajordia.

PitchminorFirstSecondP

dia.choicechoice1.22181.251.421101.51.567121.751.7131422.0131622.459182.52.850202.53.242202.53.6882434.1342734.917303.5

Basic

pitchdia.7.1889.02610.86312.70114.70116.37618.37620.37622.05125.05127.727

BasicBasicmajordia.

PitchminorFirstSecondP

dia.choicechoice6.647333.58.37636410.10639411.835424.513.835454.515.29448517.29452519.294565.520.752605.523.75264626.211

Basicpitchdia.30.72733.40236.40239.07742.07744.75248.75252.42856.42860.103

Basicminordia.29.21131.67034.67037.12940.12942.58746.58750.04654.04657.505

11AS1275—1985

3.4.2Internalthreads.ThesystemprovidestwofundamentaldeviationsforinternalthreadsdesignatedHandG.ValuesforthefundamentaldeviationsaregiveninTable3.2.Thedeviationsareapplicabletothepitchdiameterandminordiameter,andshouldbealgebraicallyaddedtothebasicpitchdiameterorbasicminordiameterasrelevant.

3.4.3Externalthreads.Thesystemprovidesthreefundamentaldeviationsforexternalthreadsdesignatede,fandg.ValuesforthefundamentaldeviationsaregiveninTable3.2.Thedeviationsareapplicabletothepitchdiameterandmajordiameter,andshouldbealgebraicallyaddedtothebasicpitchdiameterorbasicmajordiameterasrelevant.

3.5TOLERANCEGRADES.

3.5.1General.Thisstandardcoverstolerancegrades6and8forexternal(bolt)threadsandtolerancegrade6onlyforinternal(nut)threads.Thetolerancesareapplicabletothemajordiameterandpitchdiameter,forexternalthreads,andthepitchdiameterandminordiameter,forinternalthreads.ValuesforthetolerancegradesaregiveninTable3.2.

Forinformationonthethreadroottolerances,seeClause3.5.2.

3.5.2Rootdiametertolerances.

3.5.2.1Internalthreads.AsindicatedinClause2.6.1,nospecifictolerancesaregivenforthemajordiameter

ofinternalthreads.Thisparameterisconsideredacceptable,providedthatnoportionoftherootcurvaturetransgressesthebasicprofile.Forconveniencetheminimummajordiameterisgiveninthetabulatedvaluesofscrewthreadlimits(seeTable3.3).

3.5.2.2Externalthreads.AsindicatedinClause2.6.2,nospecifictolerancesaregivenfortheminordiameterofexternalthreads.Thisparameterisconsideredacceptable,providedthattherootcurvatureisinagreementwithClause2.6.2andtheminimumminordiameterisnotlessthanthatspecifiedfortheappropriatetoleranceclassinTable3.3.3.6TOLERANCECLASSES.

3.6.1General.ThemethodofdefiningatoleranceclassforISOmetricscrewthreadscomprisestwoelements,andconsistsofanumberdescribingtheselectedtolerancegrade,followedbyanupperorlowercaseletterdescribingtheselectedfundamentaldeviation—e.g.

Externalthreads:6g6hInternalthreads:6H6G.

NOTE:ThetoleranceclasssystemformetricscrewthreadsasgiveninthisstandardissimilarbutinnowayrelatedtothegeneralsystemforlimitsandfitsasgiveninAS1654.

TABLE3.2

TOLERANCESANDDEVIATIONS

Lengthofaxialengagement

NOver

1.61.8*22.2*2.533.5*44.5*568101214*1618*2022*2427*3033*3639*4245*4852*5660*64

Externalthreads

Fundamentaldeviatione—————0.0500.0530.0560.0560.0600.0600.0630.0670.0710.0710.0710.0800.0800.0800.0850.0850.0900.0900.0950.0950.1000.1000.1060.1060.1120.1120.118

f0.0340.0340.0340.0350.0350.0360.0360.0380.0380.0380.0400.0420.0450.0480.0520.0520.0580.0580.0580.0630.0630.0700.0700.0750.0750.0800.0800.0850.0850.0900.0900.095

g0.0190.0190.0190.0200.0200.0200.0210.0220.0220.0240.0260.0280.0320.0340.0380.0380.0420.0420.0420.0480.0480.0530.0530.0600.0600.0630.0630.0710.0710.0750.0750.080

Tolerance

Grade6MajorPitchdia.dia.

0.0630.085

0.0670.095

0.1000.071

0.0710.100

0.1060.075

0.0850.125

0.0900.140

0.0950.150

0.1800.112

0.1180.212

0.1320.236

0.1500.265

0.1600.280

0.3350.1700.3350.170

0.1700.335

0.2000.375

0.2120.425

0.4250.2120.4750.2240.4750.2240.5000.2360.5000.236

0.2500.530

0.2650.560

0.6000.280

Grade8

MajorPitchdia.dia.

——

0.1500.236

0.1800.280

0.3350.190

0.2120.375

0.4250.236

0.2500.450

0.2650.530

0.5300.2650.6000.3150.6000.315

0.3350.670

0.6700.335

0.3550.750

0.8000.3750.8000.3750.8500.4000.8500.400

0.4250.900

0.4500.950

Basic

majordia.D,d

PitchP

0.350.350.40.450.450.50.60.70.750.811.251.51.75222.52.52.5333.53.5444.54.5555.55.560.80.811.31.31.51.722.22.534568810101012121515181821212424282832

Upto2.62.633.83.84.5566.77.59121518242430303036364545535363637171858595

millimetres

Internalthreads

FundamentalTolerancedeviationHGGrade6

+MinorPitch0

0000000000000000000000000000000

0.0190.0190.0190.0200.0200.0200.0210.0220.0220.0240.0260.0280.0320.0340.0380.0380.0420.0420.0420.0480.0480.0530.0530.0600.0600.0630.0630.0710.0710.0750.0750.080

dia.0.1000.1000.1120.1250.1250.1400.1600.1800.1900.2000.2360.2650.3000.3350.3750.3750.4500.4500.4500.5000.5000.5600.5600.6000.6000.6700.6700.7100.7100.7500.7500.800

dia.0.0850.0850.0900.0950.0950.1000.1120.1180.1180.1250.1500.1600.1800.2000.2120.2120.2240.2240.2240.2650.2650.2800.2800.3000.3000.3150.3150.3350.3350.3550.3550.375

Secondchoicediameter.

AS1275—198512

TABLE3.3

LIMITINGDIMENSIONSFORMETRICCOARSEPITCHSERIES

SCREWTHREADS

millimetres

Basicmajordia.D,d1.61.822.2*2.533.544.5*5

PitchP0.350.350.40.450.450.50.60.70.750.8

Toler-anceclass6g6f6g6f6g6f6g6f6g6f6g6f6e6g6f6e6g6f6e6g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e

Externalthreads

MajorPitchdiameterdiametermax.min.max.min.1.5811.5661.7811.7661.9811.9662.1802.1652.4802.4652.9802.9642.9503.4793.4643.4473.9783.9623.9444.4784.4624.4444.9764.9764.9624.9405.9745.9745.9605.9407.9727.9727.9587.9379.9689.9689.9559.93311.96611.96611.95211.92913.96213.96213.94813.92915.96215.96215.94815.92917.95817.95817.94217.92019.95819.95819.94219.92021.95821.95821.94221.920

1.4961.4811.6961.6811.8861.8712.0802.0652.3802.3652.8742.8582.8443.3543.3393.3223.8383.8823.8044.3384.3224.3044.8264.7404.8124.7905.7945.6945.7805.7607.7607.6377.7467.7259.7329.5939.7199.69711.70111.54111.68711.66413.68213.51213.66813.64915.68215.51215.66815.64917.62317.42817.60717.58519.62319.42819.60719.58521.62321.42821.60721.585

1.3541.3391.5541.5391.7211.7061.8881.8732.1882.1732.6552.6392.6253.0893.0743.0573.5233.5073.4893.9913.9753.9574.4564.4564.4424.4205.3245.3245.3105.2907.1607.1607.1467.1258.9948.9948.9818.95910.82910.82910.81510.79212.66312.66312.64912.63014.66314.66314.64914.63016.33416.33416.31816.29618.33418.33418.31818.29620.33420.33420.31820.296

1.2911.2761.4911.4761.6541.6391.8171.8022.1172.1022.5802.5642.5503.0042.9892.9723.4333.4173.3993.9013.8853.8674.3614.3064.3474.3255.2125.1445.1985.1787.0426.9707.0287.0078.8628.7828.8498.82810.67910.59310.66510.64212.50312.41312.48912.47014.50314.41314.48914.47016.16416.06916.14816.12618.16418.06918.14818.12620.16420.06920.14820.126

MinorStressdiameterareaAs

min.mm21.0751.0601.2751.2601.4081.3931.5391.5241.8391.8242.2722.2562.2422.6352.6202.6033.0022.9862.9683.4393.4233.4053.8683.8143.8543.8344.5974.5284.5834.5636.2726.2006.2586.2377.9387.8587.9257.9039.6029.5169.5889.56511.27111.18111.25711.23813.27113.18113.25713.23814.62414.52914.60814.58616.62416.52916.60816.58618.62418.52918.60818.586

1.271.72.072.483.395.036.788.7811.314.2

Internalthreads

Toler-MajorPitch

ancediameterdiameterclassmin.max.min.6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G6H6G

1.6001.6001.8001.8002.0002.0002.2002.2002.5002.5003.0003.0003.5003.5004.0004.0004.5004.5005.0005.0006.0006.0008.0008.00010.00010.000

1.4581.4771.6581.6771.8301.8492.0032.0232.3032.3232.7752.7953.2223.2433.6633.6854.1314.1534.6054.6295.5005.5267.3487.3769.2069.238

1.3731.3921.5731.5921.7401.7591.9081.9282.2082.2282.6752.6953.1103.1313.5452.5764.0134.0354.4804.5045.3505.3767.1887.2169.0269.058

Minordiametermax.min.1.3211.3401.5211.5401.6791.6981.8381.8582.1382.1582.5992.6193.0103.0313.4223.4443.0783.9004.3344.3585.1535.1796.9126.9408.6768.708

1.2211.2401.4211.4401.5671.5861.7131.7332.0132.0332.4592.4792.8502.8713.2423.2643.6883.7104.1344.1584.9174.9436.6476.6758.3768.408

6120.1

81.2536.6

101.558.0

121.7584.3

12.00011.06310.86312.00011.09710.89714.00012.91312.70114.00012.95112.73916.00014.91314.70116.00014.95114.73918.00016.65616.37618.00016.64216.41820.00018.60018.37620.00018.64218.41822.00020.60020.37622.00020.64220.418

10.44110.10610.47510.14012.21011.83512.24811.87314.21013.83514.24813.87315.85415.29415.78615.33617.74417.29417.78617.33619.74419.29419.78619.336

(continued)

14*2115

162157

182.5192

202.5245

22*2.5303

Secondchoicediameter.

13AS1275—1985

TABLE3.3(continued)

millimetres

Basicmajordia.D,d24

PitchP

Toler-anceclass6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e6g8g6f6e

Externalthreads

MajorPitchdiameterdiametermax.min.max.min.23.95223.95223.93723.91526.95226.95226.93726.91529.94729.94729.93029.91032.94732.94732.93032.91035.94035.94035.92535.90538.94038.94038.82538.90541.93741.93741.92041.90044.9374493744.92044.90047.92947.92947.91547.89451.92951.92951.91551.89455.92555.92555.91055.88859.92559.92559.91059.88863.92063.92063.90563.882

23.57723.35223.56223.54026.57726.35226.56226.54029.52229.27729.50529.48532.52232.27732.50532.48535.46535.19035.45035.43038.45538.19038.45038.43041.4374113741.42041.40044.43744.13744.42044.40047.39947.07947.38547.36451.39951.07951.38551.36455.36555.02555.35055.32859.36559.02559.35059.32863.32062.97063.30563.282

22.00322.00321.98821.96625.00325.00324.98824.96627.67427.67427.65727.63730.67430.67430.65730.63733.34233.34233.32733.30736.34236.34236.32736.30739.01439.01438.99738.97742.01442.01441.99741.97744.68144.68144.66744.64648.68146.68148.66748.64652.35352.35352.33852.31656.35356.35356.33856.31660.02360.02360.00859.985

21.80321.68821.78821.76624.80324.68824.78824.76627.46227.33927.44527.42530.46230.33930.44530.42533.11832.98733.10333.08336.11835.98736.10336.08338.77838.63938.76138.74141.77841.63941.76141.74144.43144.28144.41744.39648.43148.28148.41748.39652.08851.92852.07352.05156.08855.92856.07356.05159.74359.57359.72859.705

Internalthreads

MinorStressToler-MajorPitch

diameterdiameterareaAsancediameter

2classmin.mmmin.max.min.

19.95519.8403536H24.00022.31622.05119.9406G24.00022.36422.09919.91822.95522.8404596H27.00025.31625.05122.9406G27.00025.36425.09922.91825.30525.1825616H30.00028.00727.72725.2886G30.00028.06027.78025.26828.30528.1826946H33.00031.00730.72728.2886G33.00031.06030.78028.26830.65430.5238176H36.00033.70232.40230.6396G36.00033.76233.46230.61933.65433.5239766H39.00036.70235.40233.6396G39.00036.76236.46233.61936.006

35.87611216H42.00039.39239.07735.9896G42.00039.45539.14035.96939.066

38.86713066H45.00042.39242.07738.9896G45.00042.45542.14038.96941.351

41.20114736H48.00045.08744.75241.3376G48.00045.15844.82341.31645.351

45.20117586H52.00049.08748.75245.3376G52.00049.15848.82345.31648.700

48.54020306H56.00052.78352.42848.6856G56.00052.85852.50348.66352.700

52.54023626H60.00056.78356.42852.6856G60.00056.85856.50352.66356.047

55.87726766H64.00060.47860.10356.0326G64.00060.55860.18356.009

Minordiametermax.21.25221.30024.25224.30026.77126.82429.77129.82432.27032.33035.27035.33037.79937.86240.79940.86243.29743.36847.29747.36850.79650.87154.79654.87158.30558.385

min.20.75220.80023.75223.80026.21126.26429.21129.26431.67031.73034.67034.73037.12937.19240.12940.19242.58742.65846.58746.65850.04650.12154.04654.12157.50557.585

27*3

303.5

33*3.5

364

39*4

424.5

45*4.5

485

52*5

565.5

60*5.5

646

Secondchoicediameter.

AS1275—198514

3.6.2Dispositionoftoleranceclasses.ThetoleranceclassesaredisposedaboutthebasicpitchandmajordiameterforexternalthreadsandthebasicpitchandminordiameterforinternalthreadsasshowninFig.3.2.

3.6.3Selectionoftoleranceclasses.

3.6.3.1General.Thetoleranceclassesforthepitchandcrestdiameter,shallbeselectedinaccordancewithClause3.6.3.3,bearinginmindthetypeoffastener,i.e.‘precision’or’commercial’quality.3.6.3.2Lengthofaxialthreadengagement.Thetoleranceclassesgiveninthisstandardareintendedforthe‘normal’lengthofthreadengagementasgiveninTable3.2.Iftheactuallengthofthreadengagementisunknown(asinthemanufacturingofstandardbolts),thenormallengthofthreadengagementshallbeassumed.

NOTE:Forfurtherinformation,seeAS1721.

Basedontheabove,thefollowingcombinationsarerecommended:

(a)Commercialqualityfasteners—6Hnutwith8g

bolt.(b)Precisionqualityfasteners—6Hnutwith6gbolt.

NOTE:Toleranceclasses6e,6fand6G,areessentiallyprovidedfor‘preplated’screwthreaddimensions.

3.7LIMITSOFSIZE.Thelimitingdimensionsforexternalthreads,toleranceclasses6e,6f,6gand8g;andinternalthreads,toleranceclasses6Hand6GaregiveninTable3.3.

3.8COATEDTHREADS.ThelimitingdimensionsgiveninTable3.3applytothescrewthreadsbeforecoating,unlessotherwisespecified.Aftercoatingtheactualthreadprofileshallnottransgressthemaximummateriallimits,i.e.thebasicdimensionsasgiveninTable3.1.

Theaboveprovisionsapplytoallcoatedscrewthreadsexceptthosehot-dipgalvanizedinaccordancewithAS1214.

NOTE:Forfurtherinformationonelectroplatedcoatingsonthreadedcomponents,seeAS1897.

3.6.3.3Recommendedcombinations.AlthoughthereisnodirectguidancegivenbyISOforthecombinationofthreadclasses,thesemaybeinferredbyreferencetotheappropriateISOstandardsforthreadedfasteners.

Fig.3.2.RELATIVEPOSITIONOFTOLERANCECLASSES

15AS1275—1985

SECTION4.DESIGNATIONOFSCREWTHREADS

4.1SCOPEOFSECTION.ThisSectionsetsoutthedesignationsystemusedformetricscrewthreadsforfasteners,andgivesthecompletedesignation,togetherwithashorteneddesignationwhichmaybeappliedtocoarsepitchseriesthreadsascoveredbythisstandard.Provisionisalsomadefordesignatingdifferenttypesoffitsbetweeninternalandexternalthreads.

4.2COMPLETEDESIGNATIONFORINTERNALTHREADS.Thecompletedesignationofaninternalscrewthreadtothisstandardcomprisesthefollowingelementsinthefollowingorder:(a)TheletterMindicatinganISOMetricgeneral

purposescrewthread.(b)Thevalueofthebasicmajordiameterin

millimetres.(c)Thevalueofthepitchinmillimetres.

(d)Thetoleranceclassdesignationforthepitch

diameter.

EXAMPLE:

ThreaddesignationsymbolBasicmajordiameterPitch

Pitchdiametertoleranceclass

M5×0.8-5H||||||||||||||

||||

4.3COMPLETEDESIGNATIONFOREXTERNALTHREADS.Thecompletedesignationforanexternalscrewthreadwiththesametoleranceclassforthepitchdiameterandmajordiametercomprisesthesameelementsinthesameorderasgivenforinternalscrewthreads(seeClause4.2).

EXAMPLE:

ThreaddesignationsymbolBasicmajordiameterPitch

Pitchdiametertoleranceclass

M8×1-6g||||||||||||||

||||

NOTE:Forcoarsepitchseriesthreads,seealsoClause4.4.

4.4SHORTENEDDESIGNATIONFORCOARSEPITCHSERIESTHREADS.ThedesignationforcoarsepitchseriesinternalandexternalthreadsisthesameasthatgiveninClauses4.2and4.3respectively,exceptthattheindicationofpitchmaybeomitted.Thereforeifnopitchisindicatedinthedesignation,acoarsepitchseriesthreadisspecified,i.e.—M8—6eisthesameasM8×1.25-6e;andM5—5HisthesameasM5×0.8-5H.

4.5DESIGNATIONOFATHREADFIT.Afitbetweenmatinginternalandexternalthreadsisindicatedinthedesignationbythetoleranceclassoftheinternalthread,followedbythetoleranceclassfortheexternalthreadseparatedbyanobliquestroke.Example:M8-6H/6g

AS1275—198516

APPENDIXA

NOTESONTHEPRODUCTIONOFEXTERNALTHREADS

Theactualformofthecrestofanexternalthreaddependsonthemethodofmanufacture.

Ifasingle-ribbedgrindingwheelorsingle-pointcuttingtoolisused,athreadwithacompletelyflatcrestwillbeproduced,asillustratedinFig.A1(a).

Useofacrushedmulti-ribbedwheelproducesacrestprofilesimilartothatshowninFig.A1(b).

AtypicalformofcrestproducedbythethreadrollingprocessesisshowninFig.A1(c).ThecrestsofthreadsresultingfromthisprocesswillnormallyfallwhollyabovetheminimumlimitingprofileshowninFigs2.6and2.7.

Fig.A1(d)showstheformofcrestproducedbyathreadcuttingdieofnominalrootradius,viz125P.Withacorrectlyformedtool,therewillbenoseriouslossofstraightflankevenwhenitcutsathreadonminimumdiameter.

Providedthatduecareistakeninregardtothewearoftools,roundedcrestsshouldrarelyreachthedottedprofileshowninFig.2.3.

Itmaybementionedthatthefollowingadvantagesareassociatedwithboltswithroundedcrests:

(a)Boltswithroundedcrestsarelesssusceptibletodamagebyburringinhandling

andtransportthanthosehavingflatcrests,whichresultinsharp,orsemi-sharp,edgesroundtheoutsidediameterofthebolt.

(b)Troublesassociatedwithplatingarefarlessseriousifthecrestsoftheboltsare

rounded.Intheplatingofboltsbytheusualbarrelplatingprocess,theburringofflat-crestedboltscanbequiteserious,andinthestill-vatprocesstheplatingtendstobuilduproundthetwoedgesattheoutsidediameterandencroachesupontheflanks.

(a)Crestproducedbygrindingwith

asingle-ribbedwheelorcuttingwithasinglepointtool.

(b)Crestproducedbygrindingwith

acrushedmulti-ribbedwheel.

(c)Crestproducedbythread-rolling

(d)Crestproducedbyathread

cuttingdie.

Fig.A1.CRESTPROFILESRESULTINGFROMDIFFERENTPRODUCTIONMETHODS

17AS1275—1985

APPENDIXB

COMPARISONOFSYMBOLS(Notations)FORSCREWTHREADPARAMETERS

Parameter

Symbol(notation)

usedin

ISOand

AS1275—1972this

standard

DD;dDn—Ds—

d2;d2E

En—EsdD1;d1

—dn

dsd3*pPHHh—hn—hs—

——h”n

h′s

h′nh”sttntsTTnTsffnfsFFnFsrsRnCnCsTEnTEsTDnTDsTdnTdsAsAcASsASnlnunlsusH,Gh,g,eRe

—————

Majordiameter—basic