機械專業(yè)畢業(yè)設(shè)計外文翻譯--振動的定義和術(shù)語

1、<p><b>　　翻譯：</b></p><p><b>　　英文原文</b></p><p>　　Definitions and Terminology of Vibration</p><p><b>　　vibration</b></p><p>　　All

2、matter-solid, liquid and gaseous-is capable of vibration, e.g. vibration of gases occurs in tail ducts of jet engines causing troublesome noise and sometimes fatigue cracks in the metal. Vibration in liquids is almost al

3、ways longitudinal and can cause large forces because of the low compressibility of liquids, e.g. popes conveying water can be subjected to high inertia forces (or “water hammer”) when a valve or tap is suddenly closed. E

4、xcitation forces caused, say by changes in flow of fluid</p><p>　　The mechanical vibrations dealt with are either excited by steady harmonic forces ( i. e. obeying sine and cosine laws in cases of forced vib

5、rations ) or, after an initial disturbance, by no external force apart from gravitational force called weight ( i. e. in cases of natural or free vibrations). Harmonic vibrations are said to be “simple” if there is only

6、one frequency as represented diagrammatically by a sine or cosine wave of displacement against time.</p><p>　　Vibration of a body or material is periodic change in position or displacement from a static equi

7、librium position. Associated with vibration are the interrelated physical quantities of acceleration, velocity and displacement-e. g. an unbalanced force causes acceleration (a = F/m ) in a system which, by resisting, in

8、duces vibration as a response. We shall see that vibratory or oscillatory motion may be classified broadly as (a) transient; (b) continuing or steady-state; and (c) random.</p><p>　　Transient Vibrations die

9、 away and are usually associated with irregular disturbances, e. g. shock or impact forces, rolling loads over bridges, cars driven over pot holes-i. e. forces which do not repeat at regular intervals. Although transient

10、s are temporary components of vibrational motion, they can cause large amplitudes initially and consequent high stress but, in many cases, they are of short duration and can be ignored leaving only steady-state vibration

11、s to be considered.</p><p>　　Steady-State Vibrations are often associated with the continuous operation of machinery and, although periodic, are not necessarily harmonic or sinusoidal. Since vibrations req

12、uire energy to produce them, they reduce the efficiency of machines and mechanisms because of dissipation of energy, e. g. by friction and consequent heat-transfer to surroundings, sound waves and noise, stress waves thr

13、ough frames and foundations, etc. Thus, steady-state vibrations always require a continuous energy inp</p><p>　　Random Vibration is the term used for vibration which is not periodic, i. e. has no made cle

14、ar-several of which are probably known to science students already.</p><p>　　Period, Cycle, Frequency and Amplitude A steady-state mechanical vibration is the motion of a system repeated after an interval

15、of time known as the period. The motion completed in any one period of time is called a cycle. The number of cycles per unit of time is called the frequency. The maximum displacement of any part of the system from its st

16、atic-equilibrium position is the amplitude of the vibration of that part-the total travel being twice the amplitude. Thus, “amplitude” is not synonymo</p><p>　　Natural and Forced Vibration A natural vibrat

17、ion occurs without any external force except gravity, and normally arises when an elastic system is displaced from a position of stable equilibrium and released, i. e. natural vibration occurs under the action of restori

18、ng forces inherent in an elastic system, and natural frequency is a property of he system.</p><p>　　A forced vibration takes place under the excitation of an external force (or externally applied oscillatory

19、 disturbance) which is usually a function of time, e. g. in unbalanced rotating parts, imperfections in manufacture of gears and drives. The frequency of forced vibration is that of the exciting or impressed force, i. e

20、. the forcing frequency is an arbitrary quantity independent of the natural frequency of the system.</p><p>　　Resonance Resonance describes the condition of maximum amplitude. It occurs when the frequen

21、cy of an impressed force coincides with, or is near to a natural frequency of the system. In this critical condition, dangerously large amplitudes and stresses may occur in mechanical systems but, electrically, radio and

22、 television receivers are designed to respond to resonant frequencies. The calculation or estimation of natural frequencies is, therefore, of great importance in all types of vibratin</p><p>　　Damping Dampi

23、ng is the dissipation of energy from a vibrating system, and thus prevents excessive response. It is observed that a natural vibration diminishes in amplitude with time and, hence, eventually ceases owing to some restrai

24、ning or damping influence. Thus if a vibration is to be sustained, the energy dissipated by damping must be replaced from an external source.</p><p>　　The dissipation is related in some way to the relative m

25、otion between the components or elements of the system, and is caused by frictional resistance of some sort, e.g. in structures, internal friction in material, and external friction caused by air or fluid resistance call

26、ed “viscous” damping if the drag force is assumed proportional to the relative velocity between moving parts. One device assumed to give viscous damping is the “dashpot” which is a loosely fitting piston in a cylinder so

27、 tha</p><p>　　Basic Machining Operations and Machine Tools</p><p>　　Basic Machining Operations</p><p>　　Machine tools have evolved from the early foot-powered lathes of the Egyptian

28、s and John Wilkinson’s boring mill. They are designed to provide rigid support for both the workpiece and the cutting tool and can precisely control their relative positions and the velocity of the tool with respect to t

29、he workpiece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile workpiece in the form of a severely deformed chip. The chip i</p><p

30、>　　Most machining operations produce parts of differing geometry. If a rough cylindrical workpiece revolves about a central axis and the tool penetrates beneath its surface and travels parallel to the center of rotati

31、on, a surface of revolution is producedand the operation is called turning. If a hollow tube is machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface of uniform

32、ly varying diameter is called taper turning. If the tool point tr</p><p>　　Flat or plane surfaces are frequently required. The can be generated by adial turning or facing, in which the tool point moves norm

33、al to the axis of rotation. In other cases, it is more convenient to hold the workpiece steady and reciprocate the tool across it in a series of straight-line cuts with a crosswise feed increment before each cutting stro

34、ke. This operation is called planing and is carried out on a shaper. For larger pieces it is easier to keep the tool stationary and draw the workpiec</p><p>　　Multiple-edged tools can also be used. Drilling

35、uses a twin-edged fluted tool for holes with depths up to 5 10times the drill diameter. Whether the dril turns or the workpiece rotates, relative motion between the cutting edge and the workpiece is the important factor.

36、 In milling operations a rotary cutter with a number of cutting edges engages the workpiecem which moves slowly with respect to the cutter. Plane or contoured surfaces may be produced, depending on the geometry of the cu

37、tter and the</p><p>　　Basic Machine Tools</p><p>　　Machine tools are used to produce a part of a specified geometrical shape and precise size by removing metal from a ductile materila in the for

38、m of chips. The latter are a waste product and vary from long continuous ribbons of a ductile material such as steel, which are undesirable from a disposal point of view, to easily handled well-broken chips resulting fro

39、m cast iron. Machine tools perform five basic metal-removal processes: turning, planing, drilling, milling, and frinding. All other metal</p><p>　　The amount and rate of material removed by the various machi

40、ning processes may be large, as in heavy truning operations, or extremely small, as in lapping or superfinishing operations where only the high spots of a surface are removed.</p><p>　　A machine tool perform

41、s three major functions: 1.it rigidly supports the workpiece or its holder and the cutting tool; 2. it provedes relative motion between the workpiece and the cutting tools; 3. it provides a range of feeds and speeds usua

42、lly ranging from 4 to 32 choices in each case.</p><p>　　Speed and Feeds in Machining</p><p>　　Speeds feeds, and depth of cut are the three major variables for economical machining. Other variabl

43、es are the work and tool materials, coolant and geometry of the cutting tool. The rate of metal removal and power required for machining depend upon these variables.</p><p>　　The depth of cut, feed, and cutt

44、ing speed are machine settings that must be established in any metal-cutting operation. They all affect the forces, the power, and the rate of metal removal. They can be defined by comparing them to the needle and record

45、 of a phonograph. The cutting speed is represented by the velocity of the record surface relative to the needle in the tone arm at any instant. Feed is represented by the advance the needle radially inward per revolution

46、, or is the difference in po</p><p>　　Turning on Lathe Centers</p><p>　　The basic operations performed on an engine lathe are illustrated in Fig. Those operations performed on extemal surfaces w

47、ith a single point cutting tool are called turning. Except for drilling, reaming, and tapping, the operations on intermal surfaces are also performed by a single point cutting tool.</p><p>　　All machining op

48、erations, including turning and boring, can be classified as roughing, finishing, or semi-finishing. The objective of a roughing ooperation is to remove the bulk of the material sa repidly and as efficiently as possible,

49、 while leaving a small amount of material on the work-piece for the finishing operation. Finishing operations are performed to btain the final size, shape, and surface finish on the workpiece. Sometimes a semi-finishing

50、operation will precede the finishing operati</p><p>　　Generally, longer workpieces are turned while supported on one or two lathe centers. Cone shaped holes, called center holes, which fit the lathe centers

51、are drilled in the ends of the workpiece-usually along the axis of the cylindrical part. The end of the workpiece adjacent to the tailstock is always supported by a tailstock center, while the end near the headstock may

52、be supported by a headstock cener or held in a chuck. The headstock end of the workpiece may be held in a four-jar chuck, or in</p><p>　　Very precise results can be obtained by supporting the workpiece betwe

53、en two centers. A lathe dog is clamped to the workpiece; together they are driven by a driver p;ate mounted on the spindle nose. One end of the workpiece is machined; then the workpiece can be turned around in the lathe

54、 to machine the other end. The center holes in the workpiece serve as precise locating surfaces as well as bearing surfaces to carry the weight of the workpiece and to resist the xutting forces. After the workp</p>

55、<p>　　While very large diameter workpieces are sometimes mounted on two centers, they are preferably held at the headstock end by faceplate jaes to obtain the smooth power transmission; moreover, large lathe dogs

56、that are adequate to transmit the power not generally available, although they can be maed as a special. Faceplate jaws are like chuck jaws except that thet are mounted on a faceplate, which has less overhang from the sp

57、indle bearings than a large chuck would have.</p><p><b>　　Boring</b></p><p>　　The boring operation is generally performed in two steps; namely, rough boring and finish boring. The ob

58、jective of the rough-boring operation is to remove the excess metal rapidly and efficiently, and the objective of the finish-boring operation is to obtain the desired size, surface finish, and location of the hole. The s

59、ize of the hole is obtained by using the trial-cut procedure. The diameter of the hole can be measured with inside calipers and outside micrometer calipers. Basic Measuring Ins</p><p>　　Cored holes and drill

60、ed holes are sometimes eccentric wwith respect to the rotation of the lathe. When the boring tool enters the work, the boring bar will take a deeper cut on one side of the hole than on the other, and will deflect more wh

61、en taking this deeper cut,with the result that the bored hole will not be concentric with the rotation of the work. This effect is corrected by taking several cuts through the hole using a shallow depth of cut. Each succ

62、eeding shallow cut causes the resulting</p><p>　　Shoulders, grooves, contours, tapers, and threads are bored inside of holes. Internal grooves are cut using a tool that is similar to an external grooving too

63、l. The procedure for boring internal shoulders is very similar to the procedure for turning shoulders.large shoulders are faced with the boring tool positioned with the nose leading, and using the cross slide to feed the

64、 tool. Internal contours can be machined using a tracing attachment on a lathe. The tracing attachment is mounted on the c</p><p><b>　　中文翻譯</b></p><p><b>　　振動的定義和術(shù)語</b>&l

65、t;/p><p><b>　　振動</b></p><p>　　所有的物質(zhì)---固體，液體和氣體-----都能夠振動，例如，在噴氣發(fā)動機尾部導(dǎo)管中產(chǎn)生的氣體振動會發(fā)出令人討厭的噪聲，而且有時還會使金屬產(chǎn)生疲勞裂縫。液體中的振動總是縱向的，而且由于液體的可壓縮性低，這種振動還會產(chǎn)生很大的力。例如，當(dāng)輸水管道的閥門或水龍頭突然關(guān)閉時，管道會遭受很大的慣省性力的作用（或稱為水擊

66、）。諸如，由于液體流動狀態(tài)改變或者轉(zhuǎn)動，往復(fù)運動零件推動平衡所產(chǎn)生的激振力，一般可以通過對各零件的精心設(shè)計和制造來使用權(quán)其得到降低。一臺常見的機器中有許多運動零件，每個零件都是潛在的振動源或沖擊激振源。設(shè)計人員需要處理好振動與噪聲的允許值與降低激振所需要的費用之間的關(guān)系。</p><p>　　所討論的振動或者由穩(wěn)態(tài)的諧振力引起的振動（也就是服從正弦或余弦定律的強迫振動），或者是在初始擾動之后，除了被稱為重量的重力

67、之外，沒有其他外力引起的振動（也就是自然或自由振動的情況）。如果僅用一個頻率的正弦或余弦波圖形就可表示位移與時間的關(guān)系，諧振就被認(rèn)為是“簡單的”。</p><p>　　一個物體或一種材料在振動時，它相對于靜平衡位置的位置變化或位移是周期性的。與振動有關(guān)的物理量是相互關(guān)聯(lián)的加速度，速度和位移。例如，一個不平衡的力在系統(tǒng)中造成的加速度（a =F/m）會因為系統(tǒng)的抵抗而引起振動作為響應(yīng)。可以看到，振動或者振蕩大致可以分

68、為三類：（1）瞬態(tài)的，（2）連續(xù)的或穩(wěn)態(tài)的，（3）隨機的。</p><p>　　瞬態(tài)振動是逐漸衰減的，而且通常與不規(guī)則的擾動有關(guān)，例如，滾動載荷通過橋梁，汽車通過坑洞，也就是在確定的期間內(nèi)不重復(fù)的力。盡管瞬態(tài)振動是振動的暫時性成分它們能夠產(chǎn)生大初始振幅和引起高的應(yīng)力。在大多數(shù)情況下，它們持續(xù)的時間很短，因而人們可以將其忽略不計而只考慮穩(wěn)態(tài)振動。</p><p>　　穩(wěn)態(tài)振動通常和機器的連續(xù)

69、運轉(zhuǎn)在關(guān)，而且盡管這種振動是周期性的，但不一定是諧振或正弦振動。由于需要能量才能產(chǎn)生振動，因此，振動消耗了能量，降低了機器和機構(gòu)的效率。能量的消耗有多種方式，磨擦和隨后將所產(chǎn)生的熱傳到周圍，聲波和噪聲，以及通過機架與基礎(chǔ)的應(yīng)力波等到。因此穩(wěn)態(tài)振動總是需要連續(xù)的能量輸入來維持其存在。</p><p>　　隨機振動是一個用來描述非周期性振動的術(shù)語。也就是說，這種振動不是周期性變化的，是不定期地進(jìn)行重復(fù)的。</p

70、><p>　　在下面段落中，對一些與振動有關(guān)的術(shù)語和定義加以明確，其中一些可能是理科學(xué)生都已經(jīng)清楚了的。</p><p>　　周期，循環(huán)，頻率和振幅。 穩(wěn)態(tài)機械振動是系統(tǒng)在一定時間范圍內(nèi)的重復(fù)運動，該時間范圍被稱為周期。在任何一個周期內(nèi)所完成的運動，被子稱為一個循環(huán)。每個單位時間內(nèi)的循環(huán)數(shù)目被稱為頻率。系統(tǒng)任何部分離開它的靜平衡位置的最大位移就是該部分振動的振幅，總的行程是振幅的兩倍。因此，“

71、振幅”并不是“位移”的同義詞，而是距離靜平衡位置的位移最大值。</p><p>　　自由振動和強迫振動。除了重力以外，在沒有任何其他作用時產(chǎn)生的振動稱為自由振動。通常一個彈性系統(tǒng)離開它的穩(wěn)定平衡位置后且被松開時，這個系統(tǒng)就會產(chǎn)生振動。也就是說，自由振動是在彈性系統(tǒng)固有彈性恢復(fù)力的作用下產(chǎn)生的，而固有頻率則是系統(tǒng)的一個特性。</p><p>　　強迫振動是在外力的激勵（或者外部的振蕩性干擾）

72、下產(chǎn)生的。這個激勵或干擾通常是時間的函數(shù)。例如，在不平衡的轉(zhuǎn)動部件中，或者是在有缺陷的齒輪和傳動裝置中就會產(chǎn)生這種振動。強迫振動的頻率就是激振力或者外部施加的力的頻率。也就是說，強迫振動的頻率是一個與系統(tǒng)固有頻率沒有關(guān)系的任意量。</p><p>　　共振。共振描述了最大振幅的狀況。當(dāng)外力的頻率與系統(tǒng)的固有頻率相同或相近時就會產(chǎn)生共振。在這種臨界條件下，機械系統(tǒng)中出現(xiàn)具有危險性的在振幅和高應(yīng)力。但是，電學(xué)上，收音

73、機和電視機的接收器則被設(shè)計成在共振頻率時工作。因此，在所有各種振動或振蕩系統(tǒng)中，計算或者估計系統(tǒng)的固有頻率是非常重要的。</p><p>　　阻尼。阻尼是振動系統(tǒng)中能量被消耗的現(xiàn)象，它可以防止過量的響應(yīng)?？梢杂^察到，自由振動的振幅會隨時間而衰減，因而，振動最終將由于某些限制或阻尼的影響而停止。因此，如果要使振動持續(xù)下去，一定要有外部的能源對由于阻尼而耗散的能量進(jìn)行補充。</p><p>　

74、　能量耗散以某種方式與系統(tǒng)的部件或元件之間的相對運動有關(guān)，它是由于某種類型的磨擦引起的。例如，在結(jié)構(gòu)中，材料內(nèi)部的磨擦和由空氣可液體阻力等造成的外部磨擦被稱為“粘性”阻尼，在這里假定阻力與運動部件之間的速度成正比。一種能夠提供黏性阻尼的裝置被稱為“阻尼器”。它是由一個缸體與一個活塞松馳配合形成的，液體能夠從活塞的一端通過環(huán)形間隙流到另一端。阻尼器不能存儲能量，僅能消耗能量。</p><p>　　基本的加工工序和機

75、床</p><p><b>　　基本的加工工序</b></p><p>　　機床是從早期的埃及人的腳踏動力車床和約翰·威爾金森的鏜床發(fā)展而來。它們用于為工件和刀具兩者提供剛性支承并且可以精確控制它們的相對位置和相對速度?；旧现v，在金屬切削中一個磨尖的楔形工具以緊湊螺紋形的切屑形式從有韌性工件表面去除一條很窄的金屬。切屑是廢棄的產(chǎn)品，與其工件相比相當(dāng)短但是比

76、未切屑的部分有相對的增加。機器表面的幾何形狀取決于刀具的形狀以及加工操作過程中刀具的路徑。</p><p>　　大多數(shù)加工工序生產(chǎn)出不同幾何形狀的部件。如果一個粗糙的柱形工件繞中心軸旋轉(zhuǎn)而且刀具穿破工件表面并沿與旋轉(zhuǎn)中心平行的方向前進(jìn)，就會產(chǎn)生一個旋轉(zhuǎn)面，這道工序叫車削。如果以類似的方式加工一根空心管的內(nèi)部，則這道工序就叫鏜削。制造一個直徑均勻變化的錐形外表面叫做錐體車削。如果刀具尖端以一條半徑可變的路徑前進(jìn)，就

77、可以制造出像保齡球桿那種仿形表面；如果工件足夠短而且支承具有足夠的剛性，仿形表面可以通過進(jìn)給一個垂直于旋轉(zhuǎn)軸的仿形工具來制造。短的錐面或柱面也可以仿形切削。</p><p>　　常常需要的是平坦的或平的表面。它們可以通過徑向車削或端面車削來完成，其中刀具尖端沿垂直于旋轉(zhuǎn)軸的方向運動。在其他情況下，更方便的是固定工件不動，以一系列直線式切削的方式往復(fù)運動刀具橫過工件，在每次切削行程前具有一定橫向進(jìn)給量。這種龍門刨削

78、，和牛頭刨削是在刨床上進(jìn)行的。大一些的工作很容易保持刀具固定不動，而像龍門刨削那樣在其下面拉動工件，在每次往復(fù)時進(jìn)給刀具。仿形面可以通過使用仿形刀具來制造。</p><p>　　也可以使用多刃刀具。鉆削使用兩刃刀具，孔深可達(dá)鉆頭直徑的5～10倍。不管是鉆頭轉(zhuǎn)動還是工件旋轉(zhuǎn)，切削刃與工件之間的相對運動是一個重要因數(shù)。在銑削作業(yè)中，有許多切削刃的旋轉(zhuǎn)銑刀與工件相接合，這種工件相對銑刀運動緩慢。根據(jù)銑刀的幾何形狀和進(jìn)給

79、的方式，可以加工出平面和仿形面?？梢允褂盟交虼怪毙D(zhuǎn)軸，工件可以沿三個坐標(biāo)方向中的任意一個進(jìn)給。</p><p><b>　　基本的機床</b></p><p>　　機床用于以切屑的形式從韌性材料上去除金屬來加工特殊幾何形狀和精密尺寸的部件。切屑是廢品，其變化形狀從像鋼這樣的韌性材料的長的連續(xù)帶狀屑到鑄鐵形成的易于處理、徹底斷掉的切屑，從處理的觀點來講，不想要長的連

80、續(xù)帶狀屑。機床完成5種基本的金屬切削工藝：車削、刨削、鉆削、銑削和磨削。其它所有金屬切削工藝都是這5種基本工藝的變形。例如：鏜削是內(nèi)部的車削；鉸削、錐體車削和平底锪孔則修改鉆孔，與鉆削有關(guān)；滾齒與切齒是基本銑削作業(yè)；弓鋸削和拉削是刨削和珩磨的一種形式；而研磨、超精加工、拋光和磨光則是磨削和研磨切屑作業(yè)的各種變化形式。因此，僅有4種使用專用可控幾何形狀的刀具的基本機床：1.車床2.刨床3.鉆床4.銑床。磨削工藝形成碎屑，但是磨粒的幾何形狀

81、不可控制。</p><p>　　不同的加工工藝切屑的材料的量和速度可能大，如大型車削作業(yè)；或者極小，如研磨或超精加工作業(yè)，只有表面高出的點被去除。</p><p>　　機床完成3種主要功能：1.剛性支承工件或工件夾具以及切削刀具；2.提供工件與切削刀具之間的相對運動；3.提供了一定范圍的速度和進(jìn)給，通常每種情況有4～32種選擇。</p><p><b>　

82、　加工中的速度和進(jìn)給</b></p><p>　　切割速度、進(jìn)給和深度是經(jīng)濟加工的3個主要變量，其它變量還有工件和工具的材料、冷卻劑以及切削刀具的幾何形狀。金屬切削的速率和加工所需的功率就取決于這些變量。</p><p>　　切割深度、進(jìn)給和切削速率是在任何金屬切削作業(yè)中必須都建立的機器設(shè)置。它們都影響切削力、功率和對金屬切削的速率?？梢酝ㄟ^把它們與留聲機的唱針和唱片相比較給出

83、其定義。切削速度由任意時刻唱片表面相對于拾音器支臂內(nèi)部的速度來表示；進(jìn)給由唱針每圈徑向向內(nèi)的前進(jìn)量或者由兩個相鄰槽的位置差來表示。切削的深度是唱針進(jìn)入唱片的量或者是槽的深度。</p><p><b>　　切削</b></p><p>　　在普通車床上完成的基本車削工序，那些在外表面上用單刃刀具完成的工序叫車削。除鉆削、鉸削和錐體車削外，在內(nèi)表面的作業(yè)也由單刃刀具完成。

84、</p><p>　　包括車削和鏜削在內(nèi)的所有加工工序都可以分為粗加工、精加工和半精加工。粗加工工序的目的是盡可能迅速且高效地去除大量的材料，在工件上只留下少量的材料給精加工工序。精加工工序用以獲得工件最終的大小、形狀和表面光潔度。有時，在精加工工序前進(jìn)行半精加工作業(yè)以便在工件上留下少的、預(yù)定期和均勻量的原材料供精加工去除。</p><p>　　通常，較長的工件是在一個或兩個車床頂尖的支承

85、下進(jìn)行車削的。用于安裝車床頂尖的錐形孔叫作頂尖孔，它是在工件的端部鉆出的—通常沿著柱形部件的軸心。與尾架鄰近的工件端部總是由尾架頂尖支承，而挨著主軸箱的一端則由主軸箱頂尖支承或裝在卡盤內(nèi)。工件的主軸箱一端可以裝在一個四爪卡盤內(nèi)。這種方法牢固地夾持工件并且把功率平穩(wěn)地傳送到工件；由卡盤提供的額外支承減少了車削作業(yè)時發(fā)生震動的傾向。如果仔細(xì)地將工件精確固定在卡盤上，用這種方法將可以獲得精密的結(jié)果。</p><p>　

86、　通過將工件支承在兩個頂尖之間可以獲得非常精密的結(jié)果。一個車床夾頭夾在工件上；然后由安裝在主軸前端的撥盤一起帶動。先加工工件的一端，然后可以在車床上將工件轉(zhuǎn)過來加工另一端。工件上的頂尖孔是用作精確定位面以及承受工件重量和抵抗車削力的軸承面。在工件由于任何原因被從車床上拆下后，頂尖孔可以精確地將工件裝回車床或另一臺車床，或都裝在一臺外圓磨床上。工件永遠(yuǎn)也不要同時通過卡盤和車床頂尖安裝在主軸箱端。雖然乍一想這似乎是一種在卡盤中對正工件的快捷

87、辦法，但是一定不能這么做，因為當(dāng)工件同時同頂尖支承時不可能將工件均勻地壓在爪上。由頂尖獲得的對正不能維持而且爪的壓力可能損壞頂尖孔、車床頂尖甚至車床主軸。幾乎被獨自用在大量生產(chǎn)工件上的補償或浮動爪式卡盤是上述的一個例外。這些卡盤是自動偏心夾緊卡盤不能起到普通三爪或四爪卡盤同樣的作用。</p><p>　　直徑非常大的工件雖然有時安裝在兩個頂尖上，但是最好用花盤爪把它們固定在主軸箱端以獲得流暢的動力傳輸；此外，可以

88、把它們制造成專用部件，但是一般沒有提供足夠大的車床夾頭來傳輸動力。除了是安裝在花盤上以外，花盤爪像卡盤爪，其主軸軸承上的外伸要比大卡盤上的也要少一些。</p><p><b>　　鏜削</b></p><p>　　鏜削工序一般分兩步完成，即粗鏜和精鏜。粗鏜工序的目的是快速，高效地去除多余的金屬；而精鏜工序的目的是獲得所需的尺寸、表面光潔度和孔的位置?？椎某叽缤ㄟ^使用試

89、切割程序而獲得?？椎闹睆娇梢杂脙?nèi)卡尺和外千分卡尺測量。測量儀表或內(nèi)千分卡尺可用于直接測量直徑。</p><p>　　型心孔和鉆的孔有時相對于車床的旋轉(zhuǎn)是偏心的。當(dāng)鏜孔工具進(jìn)入工件時，鏜桿在孔的一邊的切口比另一邊深，當(dāng)采用這一深切口時就會更偏斜了，結(jié)果鏜的孔不與工件旋轉(zhuǎn)同心。這一影響通過利用淺切口在整個孔加工中進(jìn)行幾次線切口來糾正。因為每個淺切口使形成的孔比使用先前切口形成的孔更加同心。在完工前，進(jìn)行精加工，孔應(yīng)該

90、與工件的旋轉(zhuǎn)同心以確保完工孔會精確定位。</p><p>　　肩、溝槽、輪廓、錐度和螺紋也應(yīng)該在孔內(nèi)鏜出。內(nèi)槽是用與外部開槽工具相擬的工具切削。鏜削內(nèi)槽的步驟非常類似于肩部的步驟。大的肩部使用前導(dǎo)裝置定位的鏜孔工具進(jìn)行刮削，使用橫向滑板進(jìn)給刀具。內(nèi)部輪廓使用車床上的描摹附件加工。仿形板附件安裝在橫向滑板上，靠模指跟隨標(biāo)準(zhǔn)剖面樣板的輪廓線運動。這使刀具對應(yīng)于標(biāo)準(zhǔn)剖面樣板的輪廓線的路徑進(jìn)行移動。這樣標(biāo)準(zhǔn)剖面樣板的輪廓