《机械专业英语》课件第5章.ppt

1、TEXT LEARN TO SPEAK NEW WORDS AND PHRASESNOTES EXERCISES READING MATERIAL PROFESSIONAL WORDS AND PHRASES Unit 5Five Basic Techniques of Machining MetalMachine tools are made in a great many types and sizesThe variety of machine tools today is almost unlimitedSome are small enough to be mounted on a

2、benchOthers are so large that they require special building to house them.Some are rather simple，while others are very complicated in construction and their controls.Large or small，simple or complicated，machine tools can be categorized into five major classifications，identified as the five basic tec

3、hniques of shaping metal.(1)DrillingDrilling is the operation of producing holes in solid metalA rotating drill called a twist drill is usedMachine tools for drilling holes are called drilling machinesThere are many types and sizes of drilling machinesThese machines can perform other operations besi

4、des drillingThe work-piece is held stationary，that is，clamped in position，and as the drill rotates，it is fed into the work-piece(as shown in Fig.5-1).(2)Turning and BoringThe engine lathe is the most common type of machine tool for turning workTurning is the operation of cutting or removing metal fr

5、om a wok-pieceA cutting tool is fed into or along the work while the work-piece revolves(as shown in Fig.5-2).Fig.5-1 Drilling Fig.5-2 Turning(3)MillingMilling is the operation of removing metal by means of a rotating cutting tool，which has multiple cutting edges and is called a milling cutter(as sh

6、own in Fig.5-4)Fig.5-3 Boring Fig.5-4 Milling(4)GrindingGrinding is the operation of cutting or removing metal by means of an abrasive wheel called a grinding wheelGrinding finishes work very accurately and smoothlyWhen grinding round work，the work-piece revolves as it is fed against the turning whe

7、elWhen grinding flat work，the work-piece is passed back and forth under the turning wheel(as shown in Fig.5-5)The grinding process is often used for the final finishing to close dimensions of a part that has been heat-treated to make it very hard(5)Shaping，Planing and SlottingThese operations are do

8、ne to produce or machine flat，accurate surface using single-point cutting toolsWe should understand the difference between the Shaper，the Planer and the slotting machinesOn a Shaper，the cutting tool moves back and forth over the work while the work is fed against the cutting tool(as shown in Fig.5-6

9、)Fig.5-5 Grinding Fig.5-6 Shaping On a Planer,the work moves back and forth under the cutting tool while the cutting tool is fed into or against the work-piece(as shown in Fig.5-7)Slotting is an operation similar to the operation performed on a ShaperA slotting machine is really a vertical Shaper，th

10、e cutting tool of which moves up and downIn this case，the work is fed against the cutting tool in a straight line or in a circle，depending upon the type of work being machinedSlotter，or vertical Shaper，are used principally to cut certain types of gearsFig.5-7 Planing LEARN TO SPEAKMr.Yang:Morning!Mr

11、.Smith:Morning!Mr.Yang:Do you know about the basic techniques of machine metal?Mr.Smith:Yes,there are five major classifications.Mr.Yang:Could you describe it in detail?Mr.Smith:OK.There are drilling,turning and boring,milling,grinding and shaping.Mr.Yang:What is drilling operation?Mr.Smith:Drilling

12、 is the operation of producing holes in solid metalMr.Yang:What is turning operation?Mr.Smith:Turning is the operation of cutting or removing metal from a wok-pieceMr.Yang:And about milling?Mr.Smith:Milling is the operation of removing metal by means of a rotating cutting tool，which has multiple cut

13、ting edges and is called a milling cutter.Mr.Yang:Does grinding finishes work very accurately and smoothly?Mr.Smith:Yes.It often used for the final finishing to close dimensions of a part that has been heat-treated to make it very hard Mr.Yang:What is the difference between the Shaper and the Planer

14、?Mr.Smith:On a Shaper，the cutting tool moves back and forth over the work while the work is fed against the cutting tool.On a Planer,the work moves back and forth under the cutting tool while the cutting tool is fed into or against the work-piece.Mr.Yang:Oh,I see.Thank you very much.Mr.Smith:My plea

15、sure.NEW WORDS AND PHRASES variety n.种类，变化，多样化 unlimited adj.无限的 bench n.工作台 house v.安装，容纳 solid adj.坚固的，固体的，实心的 n.固体，实体 slot n.缝，槽，狭槽 v.开槽 slotter n.插床，铣槽机 straight adj.直的，整齐的 circle n.环绕，旋转，圆圈 single-point cutting tool 单刃刀具 multiple cutting edges 多刃刀具 final finishing 精加工 shaping 牛头刨床 planing 龙门刨床

16、slotting 插削 slotting machine 插床 NOTES1.The variety of machine tools today is almost unlimitedSome are small enough to be mounted on a benchOthers are so large that they require special building to house them现在机床的种类太多了，一些机床小到可以安装到工作台上，另一些又大到需要用专门的厂房来安放它。so that引导结果状语从句。2.The work-piece is held statio

17、nary，that is，clamped in position，and as the drill rotates，it is fed into the work-piece 工件被固定，也就是说，被夹紧在适当位置上，钻头一边旋转一边向工件进给。that is为一插入语，意思是：也就是说，即。句中as为连词，引导状语从句。3.Boring in a lathe is done by feeding a single-point cutting tool into the work as it revolves在车床上镗孔是用一把单刃刀具向旋转的工件进刀完成的。句中by引导的介词短语作方式状语。

18、4.A slotting machine is really a vertical Shaper，the cutting tool of which moves up and down插床实际上是立式刨床，插床的刀具上下往复运动。which指A slotting machine。5.In this case，the work is fed against the cutting tool in a straight line or in a circle，depending upon the type of work being machined这时，工件向刀具对直或沿圆周进给，这取决于被加工

19、的工件的种类。against the cutting toolin a circle作方式状语，修饰动词fed。being machined是现在分词的被动语态，做定语，修饰work。EXERCISES1.Discuss the following questions in English:(1)What is the basic techniques of machining metal?(2)What is drilling operation?(3)What is the difference between the Shaper and the Planer.2.Use English

20、 replace Chinese or use Chinese replace English.(1)车削(2)镗削(3)铣削(4)slotting machine(5)cutting tool(6)a grinding wheel 3.Place a“T”after sentences that are true and an“F”after those that are false.(1)The engine lathe is the most common type of machine tool for turning work.()(2)Drilling is the operati

21、on of producing flat in solid metal.()(3)Milling is removing metal by a rotating cutting tool，which has single cutting edges and is called a milling cutter.()READING MATERIALPrinciple of MachiningTurningA high proportion of the work machined in a shop is turned on a latheThe work-piece is held secur

22、ely in a chuck or between lathe centersA turning tool，mounted in a holder and set to a given depth of cut，is fed parallel to the axis of the work to reduce the diameter of the work-piece(as shown in Fig.5-8)As the work-piece revolves and the cutting tool is fed along the axis，material is separated b

23、y the edge of the cutting toolA chip forms and slides along the cutting tools upper surface created by the side rakeThe angle of keenness(as shown in Fig.5-9)，which permits the tool to remove the metal as the tool is fed along the work-piece，is formed by the side relief angle and the side rake groun

24、d on the tool bitLets assume that we are cutting a piece of machine steel；if the rake and relief angles are correct and the proper speed and feed are used，a continuous chip should be formedIf the angle is too small，the edge of the tool will break down too soonIf the angle is too great(that is，little

25、 or no side rake)，the metal will not be removed as effectively and greater torque will be required to remove itIn either case，a built-up edge and rough surface finish will resultFig.5-8 The cutting action of a lathe or turning center Fig.5-9 Angles and clearances for lathe cutting tools PlaningThe c

26、utting tool used in the planer is basically the same shape as the lathe tool for machining similar materialsIt should have the proper rake and clearance angles ground on it to machine the work-piece efficiently.The cutting action of the planer is illustrated in Fig.5-10.The work-piece is moved back

27、and forth under the cutting tool，which is fed sideways a set amount at the end of each table reversal.Fig.5-10 The cutting action of the Planer Fig.5-11 The type of chip produced by a helical milling cutter Plain MillingA milling cutter is a multitooth tool having several equally spaced cutting edge

28、s(teeth)around its peripheryEach tooth may be considered to be a single-point cutting tool and must have proper rake and clearance angles to cut effectivelyFig.5-11 shows the chip formation produced by a helical milling cutter.The work-piece，held in a vise or fastened to the table，is fed into the ho

29、rizontal revolving cutter by hand or by automatic table feedAs the work is fed into the cutter，each tooth makes successive cuts，which produce a flat，or profiled surface，depending on the shape of the cutter used(as shown in Fig.5-12).The nomenclature of a plain milling cutter is shown in Fig.5-13.Fig

30、.5-12 As the work-piece is fed into the revolving cutter,each tooth removes material form the work Fig.5-13 The nomenclature of a plain milling cutter End and Face MillingEnd mills(as shown in Fig.5-14)are multitooth cutters held vertically in a vertical milling machine spindle or attachmentThey are

31、 used primarily for cutting slots or grooves，whereas shell end mills and face mills are used primarily for producing flat surfacesThe work-piece is held in a vise or clamped to the table and is fed into the revolving cutter by hand or automatically.When end milling，the cutting is done by the periphe

32、ry of the teethThe nomenclature of an end mill is shown in Fig.5-15.The inserted blade face mill consists of a body that holds several equally spaced inserts at the required rake angle.The lower edge of each insert has a relief or clearance angle ground on it.Fig.5-14 End mills generally cut on the

33、periphery Fig.5-15 The nomenclature of an end millDrillingThe drill is a multi-edge cutting tool that cuts on the pointThe drills cutting edges，or lips，are provided with lip clearance(as shown in Fig.5-16)to permit the point to penetrate the work-piece as the drill revolvesIt may be fed into the wor

34、k manually or automaticallyThe rake angle is provided by helical-shaped flutes that slope away from the cutting edgeAs in other cutting tools，the included angle between the rake angle and the clearance angle is known as the angle of keennessCutting-point angles for a standard drill are shown in Fig.

35、5-16 and the chip formation is shown in Fig.5-17.Fig.5-16 The characteristics of a drill point Fig.5-17 The chip formation of a drill PROFESSIONAL WORDS AND PHRASES principle n.原则，原理；准则，规范 proportion n.均衡；相称，协调 parallel adj.(指至少两条线)平行的 torque n.(尤指机器的)扭转力 multitooth adj.多齿的 periphery n.外围；边缘 vise n.虎头钳 successive adj.连续的，相继的 profiled surface n.轮廓面 nomenclature n.系统命名法；(某一学科的)术语，专门名称 attachment n.附着,附属物 multitooth tool 多刃刀具 helical-shaped flutes 螺旋槽