1、TEXT LEARN TO SPEAK NEW WORDS AND EXPRESSIONSNOTES EXERCISES READING MATERIAL PROFESSIONAL WORDS AND PHRASESUnit 3TEXTConventional Milling VS Climb Milling There are two methods of milling，i.e.conventional or up milling and climb or down milling In conventional milling，the cutter rotates against the
2、 direction of feedThis method has long been regarded as the only practical way to use milling cutters.Not long ago,climb milling was recognized as an acceptable method of operation.In climb milling，the cutter rotates in the direction of feed The advantages of climb milling are as follows:(1)Feed can
3、 frequently be doubled over conventional milling.(2)Metals can be removed fast without vibration.(3)Finish can be considerably improved(4)Tool life may be prolonged Fig.3 Two methods of milling(a)Conventional(up)milling；(b)Climb(down)milling Both conventional milling and climb milling are being empl
4、oyed，because climb milling is not applicable to any milling jobClimb milling can be applied only when the machine is of a heavy-duty type and backlash has been eliminatedClimb milling is not recommended for use on cast iron or forgings.Therefore,conventional milling remains useful in milling work LE
5、ARN TO SPEAKMr.Liu:Good afternoon,Mr.Xiong.Mr.Xiong:Good afternoon,Mr.Liu.Mr.Liu:I have some trouble with heat treatment.Could you tell me?Mr.Xiong:What are the problems?Mr.Liu:Do you know what is the function of heat treatment?Mr.Xiong:Yes.I think I see.Heat treatment is a method by which the heat
6、treater can change the physical properties of a material.Mr.Liu:How many types of heat treatment are there?Mr.Xiong:There are three main operations in the heat treatment of steel:hardening,tempering and annealing.Mr.Liu:How is hardening operation done?Mr.Xiong:The hardening operation consists of hea
7、ting the steel above its critical range and then quenching it in a suitable medium such as water,brine,oil,or some other liquid.Having been hardened,the metal must be given a tempering treatment which consists of reheating the hardened steel to a temperature below the critical range,thus producing t
8、he required physical properties.Mr.Liu:And what is critical temperature?Mr.Xiong:It is the temperature at which a certain change takes place in the physical condition of the steel.Mr.Liu:What is the purpose of annealing?Mr.Xiong:It can soften a work-piece and relieve internal stresses produced by ma
9、chining.Mr.Liu:Thank you telling me about these.Mr.Xiong:Im glad to have been of some service.NEW WORDS AND EXPRESSIONS conventional adj.一般的，常规的 VS=versus prep.对，与相对 climb v.&n.攀登，爬 i.e.=that is 即，就是 regard v.&n.认为，考虑 recognize vt.承认，认识 acceptable adj.可接受的 frequent adj.时常发生的，频繁的 frequently adv.常常，屡次
10、 double n.两倍 adj.两倍的 vt.使加倍 vi.加倍 vibration n.振动，摇动 considerable adj.相当大(或多)的，重要的 considerablely adv.相当大地 prolong vt.延长，拖延 applicable adj.可适用的，合适的 duty n.责任，功率，税 backlash n.间隙，轮齿隙 eliminate vt.排除，消除 recommend vt.推荐，介绍 cast n.铸件 v.铸造 casting n.铸造，铸件 forge n.锻工车间 v.锻造 forging n.锻造，锻件 tempering n.回火 an
11、nealing n.退火 quenching n.淬火 brine n.盐水 reheating n.重新加热 conventional milling 逆铣climb milling 顺铣up milling 逆铣down milling 顺铣regardas 认为是in a similar way 同样in this way 这样be recognized as 被认为是tool life 刀具寿命，刀具耐用度heavy-duty 重型的cast iron 铸铁as follows 如下heat treatment 热处理heat treater 热处理工作者physical proper
12、ties of a material 材料的物理性能 physical properties of a material 材料的物理性能材料的物理性能hardened steel 淬硬钢淬硬钢critical range 临界点临界点internal stress 内应力内应力critical temperature 临界温度临界温度 1There are two methods of milling，i.e.conventional or up milling and climb or down milling铣削方法有两种：逆铣(即反向铣削)与顺铣(即同向铣削)。“or”可以表示“即”的意
13、义，引出一个同位语。例如:The cutting speed must be reduced in the first,or roughing cut在初切(即粗切)时，切削速度必须降低。2In conventional milling，the cutter rotates against the direction of feed逆铣时，铣刀旋转方向与进给方向相反。“against the direction of”的含义是“与的方向相反”。NOTES 3This method has long been regarded as the only practical way to use m
14、illing cutters.这种铣削方法长期以来一直被认为是使用铣刀的唯一切实可行的方法。to v.短语可以用来修饰名词。这里的“to use”用来修饰前面的“way”。又例如：Conventional milling is not the only way to use milling cutters.逆铣不是使用铣刀的唯一方法。4In climb milling，the cutter rotates in the direction of feed顺铣时，铣刀顺着进给方向旋转。“in the direction of”的含义是“沿着的方向”。5Climb milling can be a
15、pplied only when the machine is of a heavy-duty type and backlash has been eliminated只有在机床具有相当的刚性且间隙也已消除的情况下，才能使用顺铣。“be+of+抽象名词”可以表示“具有”或“属于”等意义。句中“is of a heavy-duty type”的含义是“是重型的(刚性好的)”。再看下面两个句子：These supports are of great rigidity.这些支架具有很大的刚性。This machine is not of a heavy-duty type.这台机器不属于重型的。E
16、XERCISES1Discuss the following questions in English:(1)What is the conventional milling?(2)What is the climb milling?(3)What are the differences between the conventional milling and the climb milling?2Use English for replacing Chinese or use Chinese for replacing English.(1)进给方向(2)铣刀(3)粗切(4)Method o
17、f operation(5)The direction of feed(6)Practical way READING MATERIALRoughing and Finishing CutIt is customary，in shop practice,to take at least two cuts make a job smooth and accurateThe first cut to take is to remove excess metal from the surface of the work-piece as rapidly as possibleTo do this，t
18、he cut should be as deep and the feed as coarse as the work-piece and the machine tool will standCutting speed should be adjusted downward,if necessary，to permit thisThe first，or roughing，cut should be deep enough to size the job,with a suitable allowance for a finishing cut,in one pass whenever pos
19、sible When you intend to adjust the cutting speed or the feed to increase the rate of the production on a machine tool,it is advisable to increase the feed even though the speed must be reduced somewhatTo increase the feed rather than the cutting speed will increase production without a correspondin
20、g increase in power consumption and tool wearThe purpose of the last，or finishing，cut is to finish a work-piece smooth and accurate.To accomplish this，the cut should be shallow and the feed fine and cutting speed should be increased much higher than for the roughing cut.Roughing and finishing operat
21、ions are usually not performed on the same machine.It is a common practice，for example，to rough-turn work-pieces on a lathe,and to finish them on a grinderSome machines,abrasive machines for instance,are known to perform both roughing and finishing operations customary adj.习惯的，通常的 least adj.最小的，最少的
22、adv.最少，最小 excess n.过度，超过 adj.过度的，额外的 deep adj.深的 coarse adj.粗糙的 stand v.站，经受 downward adj.向下的 permit v.许可，允许 enough adj.足够的 n.充足 adv.足够地 PROFESSIONAL WORDS AND PHRASESrapid 5rApId adj.迅速的，快的rapidly adv.快，迅速地rate reIt n.率，比率，速度oppositely adv.在对面，相反的direction dI5rekF(E)n,daI5rekF(E)n n.方向，指导contact 5kBntAkt n.接触，触点kBn5tAkt vt.接触at least 至少even if 即使even though 即使rather than 而不at last 终于rough turn 粗车
