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T1cgh-news 发布时间: 2020-07-05 11:56:09

“幸运飞艇怎么回血稳赚”CHAPTERXXXI.PLANINGORRECIPROCATINGMACHINES.

Referringfirsttothesavingeffectedbycombiningseveraloperationsinonemachine,thereisperhapsnotoneconstructorintwentythateverstopstoconsiderwhatisreallygained,andperhapsnotonepurchaserinahundredthatdoesthesamething.Theimpressionis,thatwhenonemachineperformstwooperationsitsavesasecondmachine.AremarkableexampleofthisexistsinthemanufactureofcombinationmachinesinEuropeforworkingwood,whereitiscommontofindcomplicated[69]machinesthatwillperformalltheoperationsofajoiner'sshop,butasaruleonlyonethingatatime,andusuallyinaninconvenientmanner,eachoperationbeinghamperedandinterferedwithbyanother;andinchangingfromonekindofworktoanothertheadjustmentsandchangesgenerallyequalandsometimesexceedtheworktobedone.Whatisstrangerstillis,thatsuchmachinesarepurchased,whentheircostoftenequalsthatofseparatemachinestoperformthesamework.

[123]Againfromlearningpracticalfittingistheconfidencewhichsuchknowledgeinspiresineitherthedirectionofworkorthepreparationofplansformachinery.Anengineerwhohesitatesinhisplansforfearofcriticism,orwhodoesnotfeelaperfectconfidenceinthem,willneverachievemuchsuccess.

Shapingmachinesaredividedintotwoclasses,onemodificationwithalateralfeedofthetoolsandcutterbar,technicallycalled"travellingheadmachines,"theotherclasswithafeedmotionofthetablewhichsupportsthework,calledtable-feedingmachines.Thefirstmodificationisadaptedforlongpiecestobeplanedtransversely,suchastoothedracks,connectingrods,andsimilarwork;thesecondclasstoshorterpieceswheremuchhandadjustmentisrequired.

3.Thesavingfromcondensation,towhichsteamisexposed,avoidanceofheat,andtheconsequentcontractionandexpansionoflongconductingpipes.Theprinciplesofallmechanismforhandlingloadsshouldbesuchastoplacethepower,therateofmovement,andthedirectionoftheforce,withinthecontrolofanoperator,which,ashasbeenpointedout,isthesamethingineffectastheactionofthehumanhands.

Allmovingpartsmustofcoursebeindependentoffixedparts,therelationbetweenthetwobeingmaintainedbywhathasbeencalledrunningjoints.

Chuck-boringisemployedinthreecases;forholesofshallowdepth,taperholes,andholesthatarescrew-threaded.Aspiecesareoverhunginlathe-boringthereisnotsufficientrigidityneitherofthelathespindlenorofthetoolstoadmitofdeepboring.Thetoolsbeingguidedinastraightline,andcapableofactingatanyangletotheaxisofrotation,thefacilitiesformakingtaperedholesarecomplete;andasthetoolsarestationary,andmaybeinstantlyadjusted,thesameconditionsanswerforcuttinginternalscrew-threads;anoperationcorrespondingtocuttingexternalscrews,exceptthatthecrossmotionsofthetoolslidearereversed.

Theexpenseofformingpattern-mouldsmaybeconsideredasdividedbetweenthefoundryandpattern-shop.Whatapattern-makersavesamouldermaylose,andwhatapattern-makerspendsamouldermaysave;inotherwords,thereisapointbeyondwhichsavingexpenseinpatternsisbalancedbyextralabourandwasteinmoulding—afactthatisnotgenerallyrealisedbecauseofinaccuraterecordsofbothpatternandfoundrywork.Whatislostorsavedbyjudiciousorcarelessmanagementinthematterofpatternsandmouldingcanonlybeknowntothosewhoarewellskilledinbothmouldingandpattern-making.Amouldermaycutallthefilletsinamouldwithatrowel;hemaystopoff,fill[94]up,andprintin,tosavepattern-work,butitisonlyexpedienttodosowhenitcostsverymuchlessthantoprepareproperpatterns,becausepatchingandcuttinginmouldsseldomimprovesthem.

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网友评论

  • 雨花郡主YwVC4

    Aproofofthispropositionisfurnishedinthecaseofstandardmachinetoolsformetal-cutting,aclassofmachinerythatformanyyearspasthasreceivedthemostthoroughattentionatthehandsofourbestmechanicalengineers.

     

  • 雪灵芝YEQxy

    Inhandlingaweightwiththehandsitiscarefullyraised,andlaiddownwithcare,butmovedasrapidlyaspossiblethroughouttheinterveningdistance;thislessonofnaturehasnotbeendisregarded.Wefindthattheattentionofengineershasbeendirectedtothisprincipleofvariablespeedtobecontrolledatwill.ThehydrauliccranesofSirWilliamArmstrong,forexample,employthisprincipleinthemosteffectivemanner,notonlysecuringrapidtransitofloadswhenlifted,butdepositingoradjustingthemwithacareandprecisionunknowntomechanismpositivelygearedorevenoperatedbyfrictionbrakes.

  • 如萱紫儿fdDF8

    Amillingtoolwithtwentyedgesshouldrepresentasmuchwearingcapacityasalikenumberofseparatetools,andmaybesaidtoequaltwentyduplicatetools;hence,incuttinggrooves,notches,orsimilarwork,amillingtoolisequivalenttoalargenumberofduplicatesingletools,whichcannotbemadeorsetwiththesametruth;sothatmillingsecuresaccuracyandduplication,objectswhichareinmanycasesmoreimportantthanspeed.

  • 但法国833hL

     

  • 大笨蛋aNbTR

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  • 扒皮成dy1gf

     

  • 草莓果RiDKR

    Everyonerememberstheclassificationofwater-wheelsmetwithintheolderschool-booksonnaturalphilosophy,whereweareinformedthattherearethreekindsofwheels,astherewere"threekindsoflevers"—namely,overshot,undershot,andbreastwheels—withabriefnoticeofBarker'smill,whichranapparentlywithoutanysufficientcausefordoingso.Withoutfindingfaultwiththeplanofdescribingwater-powercommonlyadoptedinelementarybooks,fartherthantosaythatsomeexplanationoftheprinciplesbywhichpowerisderivedfromthewaterwouldhavebeenmoreuseful,Iwillventureuponadifferentclassificationofwater-wheels,moreinaccordwithmodernpractice,butwithoutreferencetothespecialmechanismofthedifferentwheels,exceptwhenunavoidable.Water-wheelscanbedividedintofourgeneraltypes.

     First.Gravitywheels,actingdirectlyfromtheweightofthewaterwhichisloadeduponawheelrevolvinginaverticalplane,theweightrestinguponthedescendingsideuntilthewaterhasreachedthelowestpoint,whereitisdischarged.

  • 绿卡纸06s6Y

    Inplaningandturning,thetoolsrequirenoexactform;theycanberoughlymade,excepttheedge,andeventhis,inmostcases,isshapedbytheeye.Suchtoolsaremaintainedatatriflingexpense,andthedestructionofanedgeisamatterofnoconsequence.Theform,temper,andstrengthcanbecontinuallyadaptedtothevaryingconditionsoftheworkandthehardnessofmaterial.Thelineofdivisionbetweenplaningandmillingisfixedbytwocircumstances—thehardnessanduniformityofthematerialtobecut,andtheimportanceofduplication.Brass,cleaniron,softsteel,oranyhomogeneousmetalnothardenoughtocauserisktothetools,canbemilledatlessexpensethanplaned,providedthereisenoughworkofauniformcharactertojustifytheexpenseofmillingtools.Cuttingtheteethofwheelsisanexamplewheremillingisprofitable,butnottotheextentgenerallysupposed.Inthemanufactureofsmallarms,sewingmachines,clocks,andespeciallywatches,wherethereisaconstantandexactduplicationofparts,millingisindispensable.Suchmanufacturesareinsomecasesfoundedonmillingoperations,aswillbepointedoutinanotherchapter.

     Shapingmachinesasmachinetoolsoccupyamiddleplacebetweenplaningandslottingmachines;theirmovementscorrespondmoretothoseofslottingmachines,whiletheoperationofthetoolsisthesameasinplaning.Someoftheadvantagesofshapingoverplaningmachinesforcertainkindsofworkare,becauseofthegreaterfacilitiesaffordedforpresentingandholdingsmallpieces,orthoseofirregularshape;thesupportsortableshavingbothverticalandhorizontalfacestowhichpiecesmaybefastened,andtheconvenienceofthemechanismforadjustingandfeedingtools.

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