Unified Inch Screw Threads (UN UNR and UNJ Thread Forms)
Date of Issuance:June30 2020
ThenexteditionofthisStandardisscheduledforpublicationin2024.ThisStandardwillbeeeffective1yearaftertheDateofIssuance.
Periodicallycertain actionsoftheASMEB1CommitteemaybepublishedasCases.CasesarepublishedontheASMEwebsite
incorrectlypublisheditems ortocorrecttypographicalorgrammaticalerrorsincodes andstandards.Such errata shallbeusedonthedateposted.
TheB1CommitteePagecanbefoundat
Committeethatapprovedthecodeorstandardwasbalancedtoassurethatindividualsfrompetentandconcernedinterestshavehadanfor additional public input from industry academia regulatory agencies and the public-at-large.
ASMEdoesnottakeanypositionwithrespecttothevalidityofanypatientrightsassertedinconnectionwithanyitemsmentionedinthisassume anysuch liability.Usersofacode orstandardare expresslyadvised thatdeterminationofthevalidityof anysuchpatentrights and theriskof infringementofsuchrights isentirelytheir ownresponsibility.
endorsementofthiscodeorstandard.
ASMEacceptsresponsibilityforonlythoseinterpretationsofthisdocumentissuedinaccordancewiththeestablishedASMEproceduresandpolicies whichprecludestheissuanceofinterpretationsbyindividuals.
Nopartof this documentmaybereproduced in anyform inanelectronicretrievalsystemorotherwise，withoutthepriorwrittenpermissionofthepublisher.
TheAmericanSocietyofMechanicalEngineersTwoParkAvenue NewYork NY10016-5990
Copyright2020byTHEAMERICANSOCIETYOFMECHANICALENGINEERSAllRightsReservedPrinted in U.S.A.
CONTENTS
Foreword.CommitteeRoster.. viiCorrespondenceWith theB1Committee viii1 General.2 Screw Thread Profile. 33 ScrewThreadSeries. 54 Screw Thread Classes.. 775 ScrewThreadAllowanceandTolerance 77ScrewThreadDesignation... 10667 DimensionalAcmodationofCoatingorPlatingfor60-DegThreads... 1108 LimitsofSizeforStandard (UN UNR and UN) andSpecial (UNS UNRS and UNJS)Seriesof115Threads....9 ThreadFormTolerances. 11710 FormulasandNomenclatureforThreadForm 14211 Tables ofBasicDimensions. 142
NonmandatoryAppendices
A Terminology and Identification of Unified InchScrew Threads. 148B Thread Strength Design Formulas . 150C Unified Inch Screw Threads-MetricTranslation. 151D Special Threads... 152E Changes toASME B1.1-1989 Tables 3A and 3B.... 161F Special Lengthsof EngagementSpecifications andDesignations 180.
Figures
1 Illustration ofAssemblyInterference of UNJ-3A Thread andUN-3B Thread in theMaximumMaterial Condition.. 22 BasicProfileforUNandUNRScrewThreads. 33 BasicProfileforUNJScrewThreads. 44 Root Radius of UNJ External Thread .. 4Disposition of Diametral Tolerances Allowance and Crest Clearance for Unified Inch Screw Thread5SeriesUN Classes 1A 2A 1B and 2B. 66 Disposition of Diametral Tolerances and Crest ClearanceforUnifiedInchScrewThreadSeriesUN Classes3Aand 3B... 77 DispositionofDiametralTolerances Allowance andCrestClearanceforUnifiedInchScrewThreadSeries UNR Classes 1A and 2A and Series UN Classes 1B and 2B... 88 Dispositionof Diametral Tolerances and Crest Clearance forUnified InchScrewThreadSeries UNR Class 3A and Series UN Class 3B..9 External UNJ Thread DesignProfile and Tolerances.. 10
10 DispositionofDiametralTolerances Allowance and CrestClearanceforUnifiedInchScrewThreadSeries UNJ Classes 2A and 2B .. 1111 Dispositionof Diametral TolerancesandCrestClearanceforUnifiedInchScrewThreadSeriesUNJ Classes3Aand3B... 1212 Internal UNj Thread DesignProfile and Tolerances .. 7813 Basic Method of DesignatingScrew Threads.... 10714 Ratio of Pitch Diameter Change to Thickness of Coating on 60-deg Threads... 11215 Effect of Electrodeposited Coating on 60-degExternal Threads.. 11316 Application of General ThreadSymbols.... 143A-1 Identification of 60-deg InchScrew ThreadsWithin theScope of theASME B1 Committee.. 148
Tables
1 Standard Series Threads(UN UNR and UNJ)... 132A Limits of Size for Standard Series External Threads (UN UNR and UNJ)... 15452B LimitsofSize forStandard SeriesInternal Threads(UN and UNJ)...3 AllowableVariations inLead and Equivalent ChangeinFunctionalDiameter. 80Increments inPitch Diameter Tolerance-Class 2A4(PD Tolerance=0.00153D0.0015√LE0.015p2). 1005 BasicProfile and Constantsfor CalculationFormulasof Thread Dimensions in.. 1026 Basic Dimensions for Coarse-Thread Series (UNC UNRC and UNJC).. 1187 Basic Dimensions for Fine-Thread Series (UNF UNRF and UNJF)... 1198 Basic Dimensions forExtra-Fine-Thread Series(UNEF UNREF and UNJEF)... 1209 Basic Dimensions for 4-Thread Series (UN UNR and UN).... 12110 Basic Dimensions for 6-Thread Series (UN UNR and UNJ).. 12311 Basic Dimensions for 8-Thread Series (UN UNR and UNJ)... 12512 Basic Dimensions for 12-Thread Series (UN UNR and UNJ).... 12713 Basic Dimensions for 16-Thread Series (UN UNR and UNJ).... 13014 Basic Dimensions for 20-Thread Series (UN UNR and UNJ)... 13315 Basic Dimensions for 28-Thread Series (UN UNR and UNJ).... 13516 Basic Dimensions for 32-Thread Series (UN UNR and UNJ).. 13617A Outline Guide for Determining Limits of Size of External Threads... 13717B Outline Guide for Determining Limits of Size of Internal Threads .. 13718A Examples of External Screw Threads .... 13818B Examples of Internal Screw Threads... 14019 AllowableVariationin30-degBasicHalfAngle ofExternal andInternalScrew Threads.. 14520 Nomenclature... 146A-1 Identification of60-degInchScrewThreadsWithin theScopeof theASMEB1 Committee.. 149Limits of SizeforSelected Combinations of UNS/UNRSSeriesThreads.... 153D-1E-1 LimitsofSizeforStandardSeriesInternalandExternalThreadsasListedinTable3AofASMEB1.1-1989... 162Limits as Listed in Table D-1 (Formerly 3B)Prior toASME B1.1-2003 Edition ..E-2 174
FOREWORD
ASME B1.1 Unified Inch Screw Threads is an integrated system of threads for fastening purposes in mechanisms andtion of threadform diameter-pitch binations and limits of size.
ThisStandardistheoutgrowthofandsupersedespreviouseditionsthatwerepublishedasASMEB1-1924 ASMEB1.1-1935 ASME B1.1-1949 ASME B1.1-1960 ASME B1.1-1974 ASME B1.1-1982 ASME B1.1-1989 andASME B1.1-2003.
The achievementsrepresented byASMEB1.1in development standardization andunification aretheresult of theSAE International (formerly Society of Automotive Engineers) National Institute of Science and Technology(formerlyNational Bureau of Standards) Committee B1 theformerNational ScrewThread Commission theformer Interdepart-mental Screw Thread Committee British Standards Institution CSA Group (formerly Canadian Standards Association) andAmericanNationalStandardsInstitute(ANSI).
ThisStandard hasits basis in thework done more than a century ago by William Sellers in the United States and SirJoseph Whitworth in Great Britain.Through theintervening years there have been many developments and revisions culminating in the Unified Thread Standard approved and adopted for use by all inch-using countries.
Theunificationofscrewthreadstandardsmeetstheneedforinterchangeabilityamongthebillionsoffastenersmadeindifferent countries and used in the plex equipment of modern technology. Unification is equally important for theinternational tradein mechanisms of all kinds and theservicingof transportation equipment thatmovesfrom country tocountry.Unificationisthereforenotonlyhighlyadvantageousbutalsoessential.
Completeunification ofcertainthreadseriesandsixtoleranceclassesinsizes7in.andlargerwasachievedwith thesigningofanaccordinWashington D.C.onNovember18 1948.Sincethattime unificationhasextendedtosmallersizes.
Developed byTechnical CommitteeNo.1 of the International OrganizationforStandardization(IsO) theunified inchbasicprofile.ThestandardwassubjecttoQuadripartiteStandardizationAgreement(QSTAG)247intheABCAArmyStandardizationProgramofAmerica Britain Canada andAustralia.
Throughout thishistory special attention has beengivento the practical aspects of thread standardization and manydetails ofAsMEB1.1result from studies and tests based onreal-world use.Forexample users municated the need forfree assembly in high-production industries and the desirability of providingfor threads that require a coating.Thetoleranceclasses2Aand2Bweredevelopedtomeetthesetwomajorrequirementsaswellastoprovideageneralstandardforexternallyandinternallythreadedfasteners.ThreadsymbolsandnomenclaturearenowconsistentwithASMEB1.7.ThreadacceptabilitynowfollowsASMEB1.3.
In1992 ASME B1.30implementedeight-place decimaland roundingrulesthataremandatoryforall neweditions andfuture revisions of ASME B1 documents.To ply with this decision the 2003edition ASME B1.1-2003
(a)revised some ofthe values in Table 2 and created Table E-1 of Nonmandatory AppendixE whichidentifies and liststherevised dimensionsfromTable 2in theASMEB1.1-1989edition.Themajority ofthedimensional changesarewithinconsidered acceptable until afuture revision of this Standard makes thevalues inTables 2A and 2Bthe only acceptablevalues.
(b)moved Table 3B which provides calculated values for various UNS (unified specials) to Nonmandatory AppendixD. The ASME B1 Committee strongly urges users to adopt the standard thread sizes in Tables 2A and 2B instead of thoselisted in Table D-1.
(c)movedTables31through 40 whichinclude some values that differ from those derived byuse of theformulas inshouldbebased oncalculations only.)
(d)eliminated all references to thread engagement from this Standard. Past changes in the thread form designation of
diameter”sinceboth characteristicshavethe samelimits of size.
f)explained in greater depth the effects of coating on threads (seesection 7).
