Presenters:ZhaoHui,YangGuoxingTianjinLightIndustryVocationalTechnicalCollegeStandardizedDimensioningImportHowtoDimensionMechanicalDrawingsToexpressitssize,dimensionsmustbemarkedonthedrawing.Thesignificanceofdimensioning251235701645Φ10Dimensionsserveasthefundamentalmanufacturingcriteriaandmustbeexact.Incorrect,incomplete,orillogicaldimensioningwillcausemachiningdifficulties,productdefects,andeconomiclosses.BasicrulesofdimensioningThepart'sactualdimensionsmuststrictlycorrespondtothenumericalvaluesspecifiedonthedrawing,independentofthedrawing'sscaleorgraphicalaccuracy.25254055552540251:21:41Basicrulesofdimensioning10010cmIftheunitisnotmm,theunitsymbolmustbeindicated.Alldimensionsonthedrawingareinmillimetersbydefaultandrequirenounitnotation.Anydeviationsfrommillimeterunitsmustbeexplicitlylabeledwiththeirrespectivemeasurementsymbols.2Thedimensionsmarkedinthedrawingshouldbethefinalfinishedsizeofthepartshowninthedrawing,otherwise,additionalexplanationisrequired.3Eachdimensionofthepartisgenerallymarkedonlyonce,andshouldbemarkedonthedrawingthatmostclearlyreflectsthestructure.4BasicrequirementsfordimensioningCorrectDimensioningmethodsmustcomplywithnationalstandards.CompleteDimensionsmustbecomplete,withoutomissionorrepetition.ClearThelayoutofdimensionsshouldbeneatandclear,easytoreadandfind.ReasonableThemarkeddimensionsshouldensuredesignrequirementsandfacilitateprocessing,assembly,andmeasurement.CompositionofdimensionsTheheightofthenumbersisabout3.5mmTheextensionlinesextendbeyondthearrowsbyabout25mmExtensionlinesArrowsDimensionlinesDimensionnumbersThespacingofdimensionlinesisabout7mm(1)Extensionlines(thinsolidlines)-indicatetherangeofthemarkeddimensions.(2)Dimensionline(thinsolidline)—indicatesthedirectionofthedimension.(3)Therearetwoformsofdimensionlineterminals:dimensionlineterminal—arrow,slash.(4)Dimensionnumbers—indicatetheactualsizeofthepart,independentofthedrawingsize.

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102035C1DimensionlinesDimensionlinesshallbedrawnasthincontinuouslines,extendingeitherfromthepart'soutline,axis,orcenterline.Alternatively,thesereferenceelementsthemselvesmayserveasdimensionlineswhenappropriate.ContourlineasdimensionlineCenterlineasdimensionlineExtensionlines251235701645Φ10702512351645Φ10CorrectErrorDimensionlinescannotbereplacedbyotherlines,andgenerallyshouldnotcoincidewithorbedrawnontheextensionofotherlines.Whenlabelinglineardimensions,thedimensionlinemustbeparalleltothelinebeinglabeled.ThedimensionlinebecomesanextensionofthecontourlineThedimensionlineisnotparalleltothecontourlineThedimensionlinecoincideswiththecontourlineThedimensionlinecoincideswiththecenterlineExtensionlinesThedimensionlinebecomesanextensionofthecenterlineThedimensionlinecoincideswiththecontourlineThedimensionlineisnotparalleltothecontourlineThedimensionlinebecomesanextensionofthecontourlineEnlargedviewofthedimensionlineterminaldd4d57.226Correct57.22657.22657.226Errorh45°Arrowshape(enlarged)Slashterminal(enlarged)Dimensionnumbers40703055703055Dimensionnumbersshouldbewritteninstandardfontandneatly.NumbersandarrowsaretoolargeNumbersandarrowsaretoosmallOnthesamedrawing,thesizeofnumbersandarrowsshouldbeconsistent.40Dimensioningmethod161616161212(a)(b)

30o161616Methodoflineardimensioning01DimensioningmethodCirclesorarcslargerthanasemicirclearegenerallydimensionedwithdiameter,thedimensionlinepassesthroughthecenter,thedimensionlineisthecircumference,andthesymbol"Φ"shouldbeaddedbeforethedimensionnumber.Semicirclesorarcssmallerthanasemicirclearegenerallydimensionedwithradius,thedimensionlineisdrawnfromthecentertothearc,andthesymbol"R"shouldbeaddedbeforethedimensionnumber.Dimensioningmethodforcircles,arcs,andsphericalsurfaces02DimensioningmethodDimensionlinesshouldbedrawnradially,dimensionlinesshouldbedrawnasarcs,thecenterofthecircleisthevertexoftheangle,dimensionnumbersshouldbewrittenhorizontally,generallyannotatedatthebreakofthedimensionline,ifnecessary,itcanalsobeannotatedoutside,orannotatedwithaleader.Whenannotatingarclengthandchordlengthdimensions,thedimensionlinesshouldbeparalleltotheperpendicularbisectorofthechord.Thedimensionlineforarclengthisaconcentricarc,andthesymbol"⌒"shouldbeaddedtotheleftofthedimensionnumber.5°25°55°10°50°25°10°50°70°30°30°Annotationmethodforangle,arclength,andchordlengthdimensions03DimensioningMethodDimensionarrowscanpointfromtheoutsidetothedimensionline,andsolidsmalldotscanbeusedinsteadofarrows,dimensionnumberscanbeannotatedwithaleaderorannotatedwithasidenote.Annotationofsmalldimensions04Examplesofcommonplanegraphicdimensionannotation⑴Determinethedimensiondatum—thesymmetrycenterlineofthegraphic,thecenterlineofthelargercircle,orthelongerstraightline.DatumDatum⑶Annotatetheshapedimension—thedimensionthatdeterminestheshapeandsizeofthelinesegmentorlineframe.?204x?12R1010060⑵Annotatethepositioningdimension—thedimensionthatdeterminestherelativepositiono