《机械制图及计算机绘图》英文课件-25 绘制螺纹

主讲人：赵慧、杨国星TianjinLightIndustryVocationalTechnicalCollegeDrawingThreadsPartIIntroductiontotheLessonPARTIIntroductiontotheLessonThread

PartIIStructureofThreadsPARTIIStructureofThreadsOnthesurfaceofacylinder(orcone),thecontinuousprotrusionsandgroovesthatfollowahelicalpathandhavethesamecross-sectionalshapearereferredtoasthreads.

Externalthreadsarethreadsformedontheoutersurfaceofacylinder(orcone).ExternalThreadsInternalThreadsInternalthreadsarethreadsformedontheinnersurfaceofacylinder(orcone).StructureofThreads0104020305ThreadProfilePitchandLeadThreadDiameterNumberofThreadsThreadDirectionStructuralElementsofThreads:FiveKeyElementsThethreadprofile,diameter,andpitcharethemostfundamentalelementsthatdeterminethestructuralspecificationsofthread.Threadswhosethreefundamentalelementsconformtonationalstandardsarereferredtoasstandardthreads.Threadswithathreadprofilethatdoesnotconformtonationalstandardsarereferredtoasnon-standardthreads.StructureofThreadsTriangularTrapezoidalSawtoothOnthesectionalviewtakenalongtheaxisofthethread,thecontourshapeofthethreadisreferredtoasthethreadprofile.Commontypesofthreadprofilesincludetriangular,trapezoidal,andsawtoothshapes.01ThreadProfileStructureofThreadsThediametersofathreadincludethemajordiameter,theminordiameter,andthepitchdiameter.Lowercaselettersareusedtorepresentexternalthreads,whileuppercaselettersareusedtorepresentinternalthreads.Thenominaldiameterofathreadreferstoitsmajordiameter.MinorDiameterD1MajorDiameterDMinorDiameterd1MajorDiameterd02ThreadDiameterStructureofThreadsSingle-threadDouble-threadThreadsareclassifiedintosingle-threadandmulti-threadtypes.Athreadformedalongasinglehelicallineiscalledasingle-thread.Athreadformedbytwoormorehelicesthatareevenlydistributedalongtheaxisiscalledamulti-thread.Thenumberofthreadsisdenotedbyn.03NumberofThreadsStructureofThreadsTheaxialdistancebetweentwopointscorrespondingtoadjacentthreadsonthemid-diameterlineofthethreadiscalledthepitch,denotedbyP.Thedistancemovedaxiallyafteronecompleterevolutionalongthesamehelicallineiscalledthelead,denotedbyPh.Forsingle-threaded,thepitchisequaltothelead:P=Ph

Formulti-threaded,thepitchmultipliedbythenumberofthreadsisequaltothelead:Ph=P×numberofthreads(n).04PitchandLeadStructureofThreads05DirectionofThreadRotationThreadsareclassifiedintoleft-handedandright-handedtypes.Athreadthatrotatesclockwiseiscalledaright-handedthread,whiletheoppositeiscalledaleft-handedthread.Themostcommonlyusedistheright-handedthread.Todeterminethedirectionofthreadrotation,onecanpositiontheaxisvertically.Ifthevisiblepartofthethreadrisesfromlefttoright,itisaright-handedthread;ifitrisesfromrighttoleft,itisaleft-handedthread.Left-handedthreadRight-handedthread

PartIIISpecifiedDrawingMethodsforThreadsPARTIII1.DrawingMethodforExternalThreadsMinordiameter=0.85ofmajordiameterMajordiameterMinordiameter30°RootLineThreadRootRadius:Drawasa3/4fine-linecircle.TherootlineisdrawnintothechamferThreadTerminationLineThreadTailCrestLineThreadCrestRadiusChamferRadius:Payattentiontothedrawingofthethreelines:CrestLine,RootLine,ThreadTerminationLineDonotdraw!SpecifiedDrawingMethodsforThreads2.MethodofDrawingInternalThreadsdonotdraw!Chamferedcircle,Minordiameter=0.85ofmajordiameterMinordiameter30°RootlineRootcircle,drawa3/4thin-linecircleThreadterminationlineThreadtailCrestlineCrestcircleMajordiameterSectionlinesdrawntothicksolidlinePayattentiontothedrawingofthethreelines:CrestLine,RootLine,ThreadTerminationLineSpecifiedDrawingMethodsforThreads3.DrawingMethodforBlindThreadedHoles120°

Drilltheholefirst

ThentaptheholeHoledepth:H0.5DThreaddepth:hDrawingMethod钻头TappingtoolSectionlinesshouldbedrawntothicksolidlines.SpecifiedDrawingMethodsforThreadsDrawingofThreadedConnectionsSpecifiedDrawingMethodsforThreadsScrew-indepthNosectionviewisrequiredNote:1、Whendrawing,ensurethatthemajorandminordiametersoftheinternalandexternalthreadsarealigned.2、Sectionlinesshouldbedrawntothicksolidlines.Internalandexternalthreadsareusedinpairs.Onlywhenthefiveelements—threadprofile,diameter,pitch,numberofthreads,anddirectionofrotation—areidenticalbetweentheinternalandexternalthreadscantheybescrewedtogether.SpecifiedDrawingMethodsforThreadsDrawingExternalThreadsDeterminethepositionoftheinternalthread'sendfaceDrawtheinternalthreadandtheprojectionoftheremainingparts0.5D0.5DSummaryofthisLectureElements