Unit19TEXT

LEARNTOSPEAKNEWWORDSANDPHRASESNOTES

EXERCISES

READINGMATERIALPROFESSIONALWORDSANDPHRASES MillingMachines

Themillingmachineisamachinethatremovesmetalfromtheworkwitharevolvingmillingcutterastheworkisfedagainstit.Themillingcutterismountedonanarborwhereitisheldinplacebyspacersorbushings.Thearborisfixedinthespindlewithoneend,whiletheotherendofthearborrotatesinthebearingmountedonthearboryoke.Fig.19-1Typeofmillingcutter

Themillingcuttersaregenerallymadefromhighspeedsteelandareavailableindifferentsizesandshapes.Therearesuchkindsofmillingcutters(asshowninFig.19-1)ascylindricalcutters,endmillingcutters(forfacemilling),formmillingcutters,angularcutters,sideandfacecutters,slittingsaw,etc.Thesecuttersmaydifferinthedirectionoftheiroperation,i.e.theymaycutrevolvingeitherclockwiseorcounter-clockwise.

Regularorirregularshapedworkmaybeproducedonamillingmachine,designsvaryingaccordingtotheparticularclassofworkwanted.Accordingtothepositionofthespindle,themillingmachinesmaybedividedintotwogroupsofverticalspindlemillingmachinesandhorizontalspindlemillingmachines.Millingmachinesmaybegroupedintovariousclasses.

Accordingtothevariationingeneraldesignasthe“columnandkneetype”,themanufacturingtypes,andtheplanertypeofmillingmachine.Accordingtothetabledesign,themillingmachinesmaybeclassifiedasuniversalandplainmillingmachines.

Themostimportantpartsofthemillingmachinearestartinglevers,spindle,column,knee,elevatingscrew,table,indexhead,speedlevers,feedlevers,tablemovementlevers,footstock,arboryoke.

Thespindleofthemillingmachineisdrivenbyanelectricmotorthroughatrainofgearsmountedinthecolumn.Thetableoftheplainmillingmachinemaytravelonlyatrightanglestothespindle,whiletheuniversalmillingmachine(asshowninFig.19-2)isprovidedwithatablethatmaybeswiveledonthetransverseslideformillinggearteeth,threads,etc.Fig.19-2Universalmillingmachine

Variousattachmentsareusedforincreasingtherangeofworkthatcanbeperformedonamillingmachine.

Thedividinghead(alsocalledanindexhead)isadeviceusedtodividetheperipheryofapieceofworkintoanynumberofequalparts,andtoholdtheworkintherequiredpositionwhilethecutsarebeingmade.

Variouskindsofvisesmaybeusedforholdingtheworkinamillingmachine,themostcommonbeingtheplainvise,andtheswivelvise.

LEARNTOSPEAK

MissLi: ?Hi,Mr.Liu.

Mr.Liu: ?Hi,MissLi.Howareyou?

MissLi: ?Iamfine.Thankyou.ButIhavesomeproblemwiththemachinetools.Couldyou??givemeafavor?

Mr.Liu: ?Yes,mypleasure.Whataretheseproblems?

MissLi: ?Whatcanshaperandplanerdo?

Mr.Liu: ?Theshaperandplaneraregenerallyusedformachiningflatsurfaces,whichare?

usuallypreformedbyacutterthatpeelthechipfromthework.

MissLi: ?Whataretheshapeandplaner’smotionforms?

Mr.Liu: ?Themainmotionisreciprocatingandthefeedaimsatthedirectionofthemain

motion.

MissLi: ?Aretheshaperandplanerusedinmassproduction?

Mr.Liu: ?No.

MissLi: ?Why?

Mr.Liu: ?Becausetheyareratherslowinoperation.

MissLi: ?But,formassproduction,whatmethodsshouldweuse?

Mr.Liu: ?Millingmachinesandgrindersaremorewidelyusedforproducingflatsurfacesin

massproduction.

MissLi: ?Whatstructuresarethereonatypicalshaper?

Mr.Liu: ?Therearetoolhead,ram,column,table,rockermechanism,etc.

MissLi: ?Howisthefeedobtainedonashaper?

Mr.Liu: ?Thefeedisobtainedbyapawlwhichengagesinanotchedwheelorratchet.

MissLi: ?Iamreallyappreciatedyoufortellingmetheseknowledge.

Mr.Liu: ?I

wasgladtobeofsomeservices.NEWWORDSANDPHRASES

removefrom 從……除去

accordingto 根據(jù)，視……而定，按照

bedividedinto 分成……

begroupedinto 分類為

beprovidedwith 裝有，備有 NOTES

1．Themillingmachineisamachinethatremovesmetalfromtheworkwitharevolvingmillingcutterastheworkisfedagainstit.銑床是一種當(dāng)工件向銑刀進給時，銑刀旋轉(zhuǎn)著從工件上切除金屬的機床。

“that”引導(dǎo)定語從句，修飾“machine”；“as”引導(dǎo)時間狀語從句，意為“當(dāng)……時候”。

2．Regularorirregularshapedworkmaybeproducedonamillingmachine,designsvaryingaccordingtotheparticularclassofworkwanted.在銑床上可以加工規(guī)則的或不規(guī)則的工件，銑床結(jié)構(gòu)的不同取決于所要加工工件的類型特點。

“irregular”一詞中，“ir-”為前綴，意為“不、非”。

3．Thetableoftheplainmillingmachinemaytravelonlyatrightanglestothespindle,whiletheuniversalmillingmachine(asshowninFig.19-2)isprovidedwithatablethatmaybeswiveledonthetransverseslideformillinggearteeth,threads,etc.普通銑床的工作臺只能沿著垂直于主軸的方向運動，而萬能銑床(?如圖19-2所示)在銑削輪齒、螺紋等時，工作臺可以在橫向滑板上轉(zhuǎn)動。

這句較長，它是由連詞“while”連接的表示轉(zhuǎn)折的并列句。在第二個句子中，“that”引導(dǎo)的從句作定語修飾“table”。 EXERCISES

1．Placea“T”aftersentencesthataretrueandan“F”afterthosethatarefalse.

(1)?Themillingmachineisamachinethatremovesmetalfromtheworkwithastationarymillingcuttersastheworkisfedagainstit.()

(2)?Alargeproportionofmillingmachinesareofthetypehavingtheworktableadjustableforheight.()

(3)?Theworktablemaybemovedlongitudinallybyhandorautomatically,inonedirection.()

(4)?Thedividinghead(alsocalledanindexhead)isadeviceusedtodividethediameterofapieceofworkintoanynumberofrequiredpositionwhilethecutsarebeingmade.()

(5)?Theverticalspindlemillingmachineissocalledbecausetheaxisofrotationofthespindleishorizontal.()

2．Filltheblankswiththewordsandexpressionsgivenbelow:

swivel(ed),most,highspeedsteel,verticallyorhorizontally,least,fixed,ordinarytoolsteel,clockwiseorcounter-clockwise,dividing,putting.

(1)?Themillingcuttersaregenerallymadefrom_______andareavailableindifferentsizesandshapes.

(2)?Theuniversalmillingmachineisprovidedwithatablethatmaybe_______onthetransverseslideformillinggearteeth,threads,etc.

(3)?Thesecuttersmaydifferinthedirectionoftheiroperation,i.e.theymaycutrevolvingeither_______or_______.

(4)?Indexingistheprocessof_______theperipheryorfaceofawork-pieceintoanynumberofequallyspaceddivisions.

(5)Variouskindsofvisesmaybeusedforholdingtheworkinamillingmachine,the_______commonbeingtheplainvise,andtheswivelvise.

3．Answerthefollowingquestions:

(1)?Definethemetal-cuttingoperationcalled“milling”.

(2)?Whatisamillingcutter?

(3)?Namethethreeprincipaltypesofmillingmachines.

(4)?Howdoesauniversalmillingmachinedifferfromaplainmillingmachine?READINGMATERIAL

GrindingMachines

Agrindingmachineisamachinewhichemploysagrindingwheelforproducingcylindrical,conicalorplanesurfacesaccuratelyandeconomicallyandtothepropershape,size,andfinish.Thesurplusstockisremovedbyfeedingtheworkagainsttherevolvingwheelorbyforcingtherevolvingwheelagainstthework.

Thereisagreatvarietyofgrindingmachines.Themachinesthataregenerallyusedarecuttergrinder,surfacegrinder,centerlessgrinder,externalgrinder,internalgrinder,andtoolgrinder.Thesemachinesareusuallyclassifiedastosizebythelargestpieceofworkwhichtheycancompletelymachine(as6×18inchExternalgrinder).

Fivetypesofgrindingoperationsareperformedongrindingmachines,asshowninFig.19-3.Fig.19-3Fivetypesofgrindingoperations

(1)?Cylindricalgrinding.Exteriorcylindersandtapersaregroundonplaingrindingmachinesandoncenterlessgrinders.

Theconstructionofuniversalgrindingmachinesissimilartothatofplaingrinders.Theyareequippedwithaninternalgrindingattachment,however,nothattheycandobothcylindricalandinternalgrinding.

(2)?Internalgrinding.Interiorcylindersandtapersaregroundoninternalgrindingmachinesandoncenterlessgrinders.

(3)Surfacegrinding.Planesurfacesaregroundonseveraltypesofsurface-grindingmachines.

(4)?Toolandcuttergrinding.Reamers,millingcuttersandothertoolsaresharpenedontoolandcuttergrindingmachines.

(5)?Formgrinding.Somemachinetoolssuchasthread,andgeargrindersaredesignedespeciallyforformgrinding.

Plaingrindingmachine.AplaingrindingmachineillustratedinFig.19-4isessentiallyalatheonwhichagrindingwheelhasbeensubstitutedforthesingle-pointtool.Fig.19-4Plaingrindingmachine

Principalpartsofaplaingrindingmachineareasfollows:

(1)?Base.Themaincastingofaplaingrindingmachineisabasethatrestsonthefloor.

(2)?Tables.Aslidingtable,whichismountedonwaysatthefrontandtopofthebase,maybemovedlongitudinallybyhandorpowertofeedwork-piecespastthefaceofthegrindingwheel.Ifthecenterlineoftheswiveltableissetatanangle,ataperwillbeground.

(3)?Headstockandtailstock.Amotor-driverheadstockandatailstockaremountedontheleftandrightends,respectively,oftheswiveltableforholdingwork-piecesoncenters.Theheadstockcen