公差与互换性国际标准05chapter3 Geometrical tolerance.docx

公差与互换性国际标准05chapter3 Geometrical tolerance.docx

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公差与互换性国际标准05chapter3Geometricaltolerance

Chapter3

Geometricaltolerance

3.1Introduction

Scopeandfieldofapplication

•ThisInternationalStandardgivestheprinciplesofsymbolizationandindicationontechnicaldrawingsoftolerancesofform,orientation,locationandrun-out,andestablishestheappropriategeometricaldefinitions.Hencetheterm“geometricaltolerances”willbeusedinthisdocumentassynonymouswiththesegroupsoftolerances.

•Geometricaltolerancesshallbespecifiedonlywheretheyareessential,thatis,inthelightoffunctionalrequirements,interchangeabilityandprobablemanufacturingcircumstances.

•Indicatinggeometricaltolerancesdoesnotnecessarilyimplytheuseofanyparticularmethodofproduction,measurementorgauging.

3.2FormandSymbolsfortolerancedcharacteristics

General

•Ageometricaltoleranceappliedtoafeaturedefinesthetolerancezonewithinwhichthefeature（surface,axis,ormedianplane）istobecontained

•Thereare14kindsofgeometricaltoleranceinISO1101;theyareshownintable3-1.

•Accordingtothecharacteristic,whichistobetoleranced,andthemannerinwhichitisdimensioned,thetolerancezoneisoneofthefollowing:

——theareawithinacircle;

——theareabetweentwoconcentriccircles;

——theareabetweentwoequidistantlinesortwoparallelstraightlines;

——thespacewithinacylinder;

——thespacebetweentwocoaxialcylinders;

——thespacebetweentwoequidistantplanesortwoparallelplanes;

——thespacewithinaparallelepiped.

•Thetolerancedfeaturemaybeofanyformororientationwithinthistolerancezone,unlessamorerestrictiveindicationisgiven,forexamplebyanexplanatorynote（seefigures3-8and3-9）.

•Unlessotherwisespecified,thetoleranceappliestothewholelengthorsurfaceoftheconsideredfeature.

•Thedatumfeatureisarealfeatureofapart,whichisusedtoestablishthelocationofadatum

•Geometricaltoleranceswhichareassignedtofeaturesrelatedtoadatumdonotlimittheformdeviationsofthedatumfeatureitself.Theformofadatumfeatureshallbesufficientlyaccurateforitspurposeanditmaythereforebenecessarytospecifytolerancesofformforthedatumfeatures.

•

Figure3-1Straightnessorflatnessofasingletolerancedfeature

Thestraightnessorflatnessofasingletolerancedfeatureisdeemedtobecorrectwhenthedistanceofitsindividualpointsfromasuperimposedsurfaceofidealgeometricalformisequaltoorlessthanthevalueofthespecifiedtolerance.Theorientationoftheideallineorsurfaceshallbechosensothatthemaximumdistancebetweenitandtheactualsurfaceofthefeatureconcernedistheleastpossiblevalue.

Possibleorientationsofthelineorsurface:

A1—B1A2—B2A3—B3

Correspondingdistances:

h1h2h3

Inthecaseoffigure1:

h1

ThereforethecorrectorientationoftheideallineorsurfaceisA1—B1.Thedistanceh1istobeequaltoorlessthanthespecifiedtolerance.

•ForthedefinitionofcircularityandCylindricity,thelocationofthetwoconcentriccirclesorcoaxialcylindersshallbechosensothattheradialdistancebetweenthemistheminimum.Possiblelocationofthecentersofthetwoconcentriccirclesortheaxesofthetwocoaxialcylindersandtheirminimalradialdistancesare:

Centre（C1）ofA1locatestwoconcentriccirclesortwocoaxialcylinders.

Centre（C2）ofA2locatestwoconcentriccirclesortwocoaxialcylinderswithminimalradialdistance:

⊿r1and⊿r2.Inthecaseoffigure3-2:

⊿r2<⊿r1.

Figure3-2Thedefinitionofcircularityandcylindricity

ThereforethecorrectlocationofthetwoconcentriccirclesorthetwocoaxialcylindersistheonedesignatedA2.Theradialdistance⊿r2shouldthenbeequaltoorlessthanthespecifiedtolerance.

Table3.1Symbolsfortolerancedcharacteristics

Featuresandtolerances

Tolerancecharacteristics

Symbols

Subclauses

Singlefeatures

Formtolerances

Straightness

3.5.1

Flatness

3.5.2

Circularity

3.5.3

Cylindricity

3.5.4

Singleorrelatedfeatures

Profileofanyline

3.5.5

Profileofanysurface

3.5.6

Relatedfeatures

Orientationtolerances

Parallelism

3.5.7

Perpendicularity

3.5.8

Angularity

3.5.9

Locationtolerances

Position

3.5.10

Concentricityandcoaxiality

3.5.11

Symmetry

3.5.12

Run-outtolerances

Circularrun-out

3.5.13

Totalrun-out

3.5.14

3.3Indicationofgeometricaltoleranceondrawing

Toleranceframe

•Thetolerancerequirementsareshowninarectangularframewhichisdividedintotwoormorecompartments.Thesecompartmentscontain,fromlefttoright,inthefollowingorder（seefigures3-3,3-4and3-5）:

Figure3-5

Figure3-4

Figure3-3Tolerancefram

—thesymbolforthecharacteristictobetoleranced;

—thetolerancevalueintheunitusedforlineardimensions.Thisvalueisprecededbythesignфifthetolerancezoneiscircularorcylindrical;

—ifappropriate,theletterorlettersidentifyingthedatumfeatureorfeatures（seefigures3-4and3-5）.

•Remarksrelatedtothetolerance,forexample“6holes”,“4surfaces”or“6x”shallbewrittenabovetheframe（seefigures3-6and3-7）.

Figure3-7Remarks

Figure3-6Remarks

•Indicationsqualifyingtheformofthefeaturewithinthetolerancezoneshallbewrittennearthetoleranceframeandmaybeconnectedbyaleaderline（seefigures3-8and3-9）.

Figure3-9Qualifyingtheformofthefeature

Figure3-8Qualifyingtheformofthefeature

•Ifitisnecessarytospecifymorethanonetolerancecharacteristicforafeature,thetolerancespecificationsaregivenintoleranceframesoneundertheother（seefigure3-10）.

Figure3-10Thetolerancespecifications

Tolerancedfeatures

•Thetoleranceframeisconnectedtothetolerancedfeaturebyaleaderlineterminatingwithanarrowinthefollowingway:

—ontheoutlineofthefeatureoranextensionoftheoutline（butclearlyseparatedfromthedimensionline）whenthetolerancereferstothelineorsurfaceitself（seefigures3-11and3-12）.

Figure3-12

Figure3-11

—asanextensionofadimensionlinewhenthetolerancereferstotheaxisormedianplanedefinedbythefeaturesodimensioned（seefigures3-13to3-15）.

Figure3-15

Figure3-14

Figure3-13

—ontheaxiswhenthetolerancereferstotheaxisormedianplaneofallfeaturescommontothataxisormedianplane（seefigures3-16,3-17and3-18）.

Figure3-18

Figure3-16

Figure3-17

•Whetheratoleranceshouldbeappliedtothecontourofacylindricalorsymmetricalfeatureortoitsaxisormedianplanerespectivelydependsonthefunctionalrequirements.

Tolerancezones

•Thewidthofthetolerancezoneisinthedirectionofthearrowoftheleaderlinejoiningthetoleranceframetothefeaturewhichistoleranced,unlessthetolerancevalueisprecededbythesignø,（seefigures3-19and3-20）.

Figure3-20

Figure3-19

•Ingeneral,thedirectionofthewidthofthetolerancezoneisnormaltothespecifiedgeometryofthepart（seefigures3-21and3-22）.

Figure3-21

Figure3-22

•Thedirectionofthewidthofthetolerancezoneshallbeindicatedwhendesirednotnormaltothespecifiedgeometryofthepart（seefigures3-23and3-24）.

Figure3-24

Figure3-23

•Individualtolerancezonesofthesamevalueappliedtoseveralseparatefeaturescanbespecifiedasshowninfigures3-25and3-26.

Figure3-26

Figure3-25

•Whereacommontolerancezoneisappliedtoseveralseparatefeatures,therequirementisindicatedbythewords“commonzone”abovethetoleranceframe（seefigures3-27and3-28）.

Figure3-28

Figure3-27

Datums

•Whenatolerancedfeatureisrelatedtoadatum,thisisgenerallyshownbydaumletters.Thesameletterwhichdefinesthedatumisrepeatedinthetoleranceframe.

•Toidentifythedatum,acapitalletterenclosedinaframeisconnectedtoasolidorblankdatumtriangle（seefigures3-29and3-30）.

Figure3-29

Figure3-30

•Thedatumtrianglewiththedatumletterisplaced:

•Ontheoutlineofthefeatureoranextensionoftheoutline（butclearlyseparatedfromthedimensionline）,whenthedatumfeatureisthelineorsurfaceitself（seefigure3-31）.

Figure3-31

—asanextensionofthedimensionlinewhenthedatumfeatureistheaxisormedianplane（seefigures3-32to3-34）

Figure3-34

Figure3-33

Figure3-32

•ifthereisinsufficientspacefortwoarrows,oneofthemmaybereplacedbythedatumtriangle（seefigures3-33and3-34）

—ontheaxisormedianplanewhenthedatumis:

✧theaxisormedianplaneofasinglefeature（forexampleacylinder）;

✧thecommonaxisorplaneformedbytwofeatures（seefigure3-35）

Figure3-35

•Ifthetoleranceframecanbedirectlyconnectedwiththedatumfeaturebyaleaderline,thedatumlettermaybeomitted（seefigures3-36and3-37）.

Figure3-37

Figure3-36

•Asingledatumisidentifiedbyacapitalletter（seefigure3-38）

•Acommondatumformedbytwodatumfeaturesisidentifiedbytwodatumlettersseparatedbyahyphen（seefigure3-39）

•Ifthesequenceoftwoormoredatumfeaturesisimportantthedatumlettersareplacedindifferentcompartments（seefigure3-40）.

•Ifthesequenceoftwoormoredatumfeaturesisnoimportantthedatumlettersareindicatedinthesamecompartment（seefigure3-41）.

Figure3-38

Figure3-41

Figure3-40

Figure3-39

Restrictivespecifications

•Ifthetoleranceisappliedtoarestrictedlength,lyinganywhere,thevalueofthislengthshallbeaddedafterthetoleranceandseparatedfromitbyanobliquestroke.

•Inthecaseofasurface,thesameindicationisused.T