Unit4TEXT

READINGMATERIALTEXTConventionalMillingVSClimbMillingTherearetwomethodsofmilling，i.e.conventionalorupmillingandclimbordownmilling．Inconventionalmilling，thecutterrotatesagainstthedirectionoffeed．Thismethodhaslongbeenregardedastheonlypracticalwaytousemillingcutters.Notlongago,climbmillingwasrecognizedasanacceptablemethodofoperation.

Inclimbmilling，thecutterrotatesinthedirectionoffeed．Theadvantagesofclimbmillingareasfollows:(1)?Feedcanfrequentlybedoubledoverconventionalmilling.(2)?Metalscanberemovedfastwithoutvibration.(3)?Finishcanbeconsiderablyimproved．(4)

Toollifemaybeprolonged．Fig.4-1Twomethodsofmilling(a)?Conventional(Up)milling；(b)?Climb(Down)millingBothconventionalmillingandclimbmillingarebeingemployed，becauseclimbmillingisnotapplicabletoanymillingjob．Climbmillingcanbeappliedonlywhenthemachineisofaheavy-dutytypeandbacklashhasbeeneliminated．Climbmillingisnotrecommendedforuseoncastironorforgings.Therefore,conventionalmillingremainsusefulinmillingwork．LEARNTOSPEAKMr.Liu: Goodafternoon,Mr.Xiong.Mr.Xiong: Goodafternoon,Mr.Liu.Mr.Liu: Ihavesometroublewithheattreatment.Couldyoutellme?Mr.Xiong: Whataretheproblems?Mr.Liu: Doyouknowwhatisthefunctionofheattreatment?Mr.Xiong: Yes.IthinkIsee.Heattreatmentisamethodbywhichtheheattreatercanchangethephysicalpropertiesofamaterial.Mr.Liu: Howmanytypesofheattreatmentarethere?Mr.Xiong: Therearethreemainoperationsintheheattreatmentofsteel:hardening,temperingandannealing.Mr.Liu: Howishardeningoperationdone?Mr.Xiong: Thehardeningoperationconsistsofheatingthesteelaboveitscriticalrangeandthenquenchingitinasuitablemediumsuchaswater,brine,oil,orsomeotherliquid.Havingbeenhardened,themetalmustbegivenatemperingtreatmentwhichconsistsofreheatingthehardenedsteeltoatemperaturebelowthecriticalrange,thusproducingtherequiredphysicalproperties.Mr.Liu: Andwhatiscriticaltemperature?Mr.Xiong: Itisthetemperatureatwhichacertainchangetakesplaceinthephysicalconditionofthesteel.Mr.Liu: Whatisthepurposeofannealing?Mr.Xiong: Itcansoftenawork-pieceandrelieveinternalstressesproducedbymachining.Mr.Liu: Thankyoutellingmeaboutthese.Mr.Xiong: I’mgladtohavebeenofsomeservice.NEWWORDSANDEXPRESSIONSconventional [kEn5venFEn(E)l] adj.一般的，常規(guī)的VS=versus [5vз:sEs] prep.對(duì)，與…相對(duì)climb [klaIm] v.&n.攀登，爬i.e.=thatis 即，就是regard [rI5^B:d] v.&n.認(rèn)為，考慮recognize [5rekE^naIz] vt.承認(rèn)，認(rèn)識(shí)acceptable [Ek5septEb(E)l] adj.可接受的frequent [5fri:kwEnt] adj.時(shí)常發(fā)生的，頻繁的frequently adv.常常，屢次double [5dQb(E)l] n.兩倍 adj.兩倍的 vt.使加倍 vi.加倍vibration [vaI5breIF(E)n] n.振動(dòng)，搖動(dòng)considerable[kEn5sIdErEb(E)l] adj.相當(dāng)大(或多)的，重要的considerablely 相當(dāng)大地prolong [prE5lBN;(?@)prEJ5lC:N] vt.延長(zhǎng)，拖延applicable [5AplIkEb(E)l] adj.可適用的，合適的duty [5dju:tI;(?@)5du:tI]n.責(zé)任，功率，稅backlash [5bAklAF] n.間隙，輪齒隙eliminate [I5lImIneIt] vt.排除，消除recommend [rekE5mend] vt.推薦，介紹cast [kB:st;(?@)kAst] n.鑄件 v.鑄造casting n.鑄造，鑄件forge [fC:dV] n.鍛工車間 v.鍛造forging鍛造，鍛件tempering v.回火annealing v.退火quenching n.淬火brine [braIn] n.鹽水reheating [ri:5hi:tIN] n.重新加熱conventionalmilling逆銑climbmilling順銑upmilling 逆銑downmilling 順銑regard…as 認(rèn)為……是inasimilarway 同樣inthisway 這樣berecognizedas 被認(rèn)為是toollife 刀具壽命，刀具耐用度heavy-duty 重型的castiron 鑄鐵asfollows 如下twistdrill 麻花鉆high-speedsteel高速鋼heattreatment熱處理heattreater 熱處理工作者physicalpropertiesofamaterial材料的物理性能hardenedsteel 淬硬鋼criticalrange 臨界點(diǎn)internalstress 內(nèi)應(yīng)力criticaltemperature 臨界溫度NOTES1．Therearetwomethodsofmilling，i.e.conventionalorupmillingandclimbordownmilling．銑削方法有兩種：逆銑(即反向銑削)與順銑(即同向銑削)?！皁r”可以表示“即”的意義，引出一個(gè)同位語(yǔ)。例如:Thecuttingspeedmustbereducedinthefirst,orroughingcut．在初切(即粗切)時(shí)，切削速度必須降低。2．Inconventionalmilling，thecutterrotatesagainstthedirectionoffeed．逆銑時(shí)，銑刀旋轉(zhuǎn)方向與進(jìn)給方向相反?！癮gainstthedirectionof……”的含義是“與……的方向相反”。3．Thismethodhaslongbeenregardedastheonlypracticalwaytousemillingcutters.這種銑削方法長(zhǎng)期以來(lái)一直被認(rèn)為是使用銑刀的惟一切實(shí)可行的方法。?tov短語(yǔ)可以用來(lái)修飾名詞。這里的“touse”用來(lái)修飾前面的“way”。又例如:Conventionalmillingisnottheonlywaytousemillingcutters.逆銑不是使用銑刀的惟一方法。4．Inclimbmilling，thecutterrotatesinthedirectionoffeed．順銑時(shí)，銑刀順著進(jìn)給方向旋轉(zhuǎn)?！癷nthedirectionof…”的含義是“沿著……的方向”。5．Climbmillingcanbeappliedonlywhenthemachineisofaheavy-dutytypeandbacklashhasbeeneliminated．只有在機(jī)床具有相當(dāng)?shù)膭傂郧议g隙也已消除的情況下，才能使用順銑?！癰e+of+抽象名詞”可以表示“具有”或“屬于”等意義。句中“isofaheavy-dutytype”的含義是“是重型的(剛性好的)”。再看下面兩個(gè)句子：Thesesupportsareofgreatrigidity.這些支架具有很大的剛性。Thismachineisnotofaheavy-dutytype.這臺(tái)機(jī)器不屬于重型的。EXERCISES1．DiscussthefollowingquestionsinEnglish:(1)?Whatistheconventionalmilling?(2)?Whatistheclimbmilling?(3)?Whatarethedifferencesbetweentheconventionalmillingandtheclimbmilling?2．UseEnglishforreplacingChineseoruseChineseforreplacingEnglish.(1)進(jìn)給方向(2)銑刀(3)粗切(4)?Methodofoperation(5)?Thedirectionoffeed(6)?PracticalwayREADINGMATERIALRoughingandFinishingCutItiscustomary，inshoppractice,totakeatleasttwocutsmakeajobsmoothandaccurate．Thefirstcuttotakeistoremoveexcessmetalfromthesurfaceofthework-pieceasrapidlyaspossible．Todothis，thecutshouldbeasdeepandthefeedascoarseasthework-pieceandthemachinetoolwillstand．Cuttingspeedshouldbeadjusteddownward,ifnecessary，topermitthis．Thefirst，orroughing，cutshouldbedeepenoughtosizethejob,withasuitableallowanceforafinishingcut,inonepasswheneverpossible．Whenyouintendtoadjustthecuttingspeedorthefeedtoincreasetherateoftheoftheproductiononamachinetool,itisadvisabletoincreasethefeedeventhoughthespeedmustbereducedsomewhat．Toincreasethefeedratherthanthecuttingspeedwillincreaseproductionwithoutacorrespondingincreaseinpowerconsumptionandtoolwear．Thepurposeofthelast，orfinishing，cutistofinishawork-piecesmoothandaccurate.Toaccomplishthis，thecutshouldbeshallowandthefeedfineandcuttingspeedshouldbeincreasedmuchhigherthanfortheroughingcut.Roughingandfinishingoperationsareusuallynotperformedonthesamemachine.Itisacommonpractice，forexample，torough-turnwork-piecesonalathe,andtofinishthemonagrinder．Somemachines,abrasivemachinesforinstance,areknowntoperformbothroughingandfinishingoperations．PROFESSIONALWORDSANDPHRASEScustomary [5kQstEmErI;(?@)5kQstEmerI] adj.習(xí)慣的，通常的least [li:st] adj.最小的，最少的adv.最少，最小excess [5ekses]n.過(guò)度，超過(guò) adj.過(guò)度的，額外的deep [di:p] adj.深的coarse [kC:s] adj.粗糙的stand [stAnd] v.站，經(jīng)受downward [5daJnwEd]adj.向下的permit [pE5mIt] v.許可，允許enough [I5nQf]adj.足夠的 n.充足 adv.足夠地allowance [E5laJEns] n.(加工)余量，容差intend [In5tend] vt.想要，打算advisable [Ed5vaIzEbl] adj.可取的，明智的somewhat [5sQmwBt;(?@)-hwBt] adv.稍微，有點(diǎn)correspond [kBrI5spBnd;(?@)kC:rE5spBnd] vi.符合，