美国机械制图标准简介

1821COMMONSYMBOLS/Shownbelowarethemostcommonsymbolsthatareusedwithgeometrictolerancingandotherrelateddimensionalrequirementsonengineeringdrawings.NotethecomparisonwiththeISOstandards.Mostofthesymbologyisidentical.ThereareafewsymbolsthatareusedintheASMEY14.5,1994standardthatarebeingproposedfortheISOstandards.Thesymbolsmarkedwithan“x”areneworrevisedfromthepreviousY14.5M,1982standard./ISOASMEY14.5,1994ISO“x”Y14.5M,1982SYMBOLASMEY14.5MISOFEATURECONTROLFRAMEDIAMETER/SPHERICALDIAMETER/ATMAXIMUMMATERIALCONDITIONATLEASTMATERIALCONDITIONREGARDLESSOFFEATURESIZENONE/NONE/PROJECTEDTOLERANCEZONEXFREESTATE/XTANGENTPLANE(Proposed)XSTATISTICALTOLERANCENONE/XRADIUS/RRXCONTROLLEDRADIUS/CRNONE/SPHERICALRADIUS/SRSRBASICDIMENSION/(theoreticallyexactdimensioninISO)ISOXDATUMFEATURE**DATUMTARGETTARGETPOINT/DIMENSIONORIGINREFERENCEDIMENDION/(AuxiliarydimensioninISO)/ISO(50)(50)2822NUMBEROFPLACES/8x8xCOUNTERBORE/SPOTFACE/COUNTERSINK/DEPTH/DEEP/SQUARE/ALLAROUND/NONEDIMENSIONNOTTOSCALEARCLENGTH/XBETWEEN/NONESLOPE/CONICALTAPER/ENVELOPEPRINCIPLENONE(implied)/Note:*Maybefilledornotfilled/*RADIUS,CONTROLLEDRADIUS/Therearetwotypesofradiitolerancethatcanbeapplied,theradiusandcontrolledradius.Theradius(R)toleranceisforgeneralapplications.Thecontrolledradius(CR)isusedwhenitisnecessarytoplacefurtherrestrictionsontheshapeoftheradius,asinhighstressapplications./R(CR)Note:ThisisachangefromthepreviouseditionsoftheY14.5standard.Thedefinitionofthetolerancezonefortheformertermtangentradius,previouslynotedbythesymbolR,isnowmeanttoapplytoacontrolledradius(symbolCR)./Y14.5RCR3823STATISTICALTOLERANCINGSYMBOL/Often,tolerancesarecalculatedonanarithmeticbasis.Tolerancesareassignedtoindividualfeaturesonacomponentbydividingthetotalassemblytolerancebythenumberofcomponentsandassigningaportionofthistolerancetoeachcomponent.Whentolerancesarestackedupinthismanner,thetolerancemaybecomeveryrestrictiveortight./Statisticaltolerancingistheassignmentoftolerancestorelatedcomponentsofanassemblyonthebasisofsoundstatistics.Anexampleis:theassemblytoleranceisequaltothesquarerootofthesumofthesquaresoftheindividualtolerances./Statisticaltolerancingmaybeappliedtofeaturestoincreasetolerancesandreducemanufacturingcost.Toensurecompatibility,thelargertoleranceidentifiedbythestatisticaltolerancesymbolmayonlybeusedwhereappropriatestatisticalprocesscontrolwillbeused.Anotesuchastheoneshownbelowshallbeplacedonthedrawing./4824Note:/FEATURESIDENTIFIEDASSTATISTICALLYTOLERANCEDSHALLBEPRODUCEDWITHSTATISTICALPROCESSCONTROLS,ORTOTHEMORERESTRICTIVEARITHMETICLIMITS./Insomecases,itmaybedesirabletostateonlythestatisticaltoleranceandthearithmeticnumberwillnotbeshown.Inthiscase,anotesuchasthefollowingmustbeplacedonthedrawing./FEATURESIDENTIFIEDASSTATISTICALLYTOLERANCEDSHALLBEPRODUCEDWITHSTATISTICALPROCESSCONTROLS./Foradditionalinformationonstatisticaltolerancing,seeappropriatestatisticsorengineeringdesignmanuals./NONRIGIDPARTS-FREESTATECONDITION/-Unlessotherwisespecified,alldimensioningandtolerancingappliesinaFreeStateconditionwithnorestraint.Someparts,suchassheetmetal,thinmetal,plasticsandrubberarenorigidinnature.ItmaybenecessarytospecifydesignrequirementsonthepartinanaturalorFreeStateaswellasinarestrainedcondition.Therestraintorforceonthenonrigidpartsisusuallyappliedinsuchamannertoresembleorapproximatethefunctionalormatingrequirements./5825Anoteorspecificationonthedrawingshouldexplainhowthepartisrestrainedandtheforcerequiredtofacilitatetherestraint.Asamplenotecanbefoundonthedrawingbelow./Ifanyofthepartspecificationsaretobeverifiedinafreestate,thedesignermayspecifythisrequirementwiththewordsFREESTATEorthefreestatesymbol.ThefreestatesymbolisaFinacircle.Thefreestatesymbolmeansthatdimensionsandtolerancesthathavethefreestatesymbolappliedarecheckedinthefreestateandnotintherestrainedcondition./FThefreestatesymbolisappliedbyplacingitnexttoorassociatingitwiththerequireddimensionsandtolerances.Ifitisappliedinafeaturecontrolframe,italwaysfollowsthefeaturetoleranceandanymodifiers./4M5A6826FEATURECONTROLFRAME/Afeaturecontrolframestatestherequirementsorinstructionsforthefeaturestowhichitisattached./SYMBOLSTHATCANBEFOUNDINAFEATURECONTROLFRAME/Allofthesymbolsbelowcanbefoundinsideafeaturecontrolframe.Thesymbolsforprojectedtolerancezone,freestate,tangentplaneandstatisticaltolerancealwaysfollowthematerialconditionmodifierTheminimumheightoftheprojectedtolerancezonecanbespecifiedinthefeaturecontrolframeorintheviewonthedrawinginwhichitapplies.Ifitisappliedinthefeaturecontrolframe,itfollowstheprojectedtolerancezonesymbol./TERM/SYMBOL/FEATURECONTROLFRAME/DIAMETER/SPHERICALDIA/MAXIMUMMATERIALCOND/LEASTMATERIALCOND/PROJECTEDTOLZONE/FREESTATE/TANGENTPLANE/STATISTICALTOLERANCE/REGARDLESSOFFEATURESIZE*/**TheRFSsymbolhasbeeneliminatedfromtheASMEY14.5M,1994standard.Itisapplicableinearlierversions./*RFSASMEY14.5M,19947827DATUMFEATURESYMBOL/Y14.5M,1982ANDEARLIERY14.5M,1994ANDISO/Y14.5M,1982/Y14.5M,1994ISOMATERIALCONDITIONMODIFIERS–DEFINITIONS/-Ingeometrictolerancingthereisoftenaneedtorefertoaparticularfeatureofsizeatitslargestsize