0英文原文LATHES & MILLINGA shop that is equipped with a milling machine and an engine lathe can machine almost any type of product of suitable size.The basic machines that are designed primarily to do turning，facing and boring are called lathes. Very little turning is done on other types of machine tools， and none can do it with equal facility. Because lathe can do boring， facing，drilling，and reaming in addition to turning，their versatility permits several operations to be performed with a single setup of the workpiece. These accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool. Lathes in various forms have existed for more than two thousand years. Modern lathes date from about 1797，when Henry Maudsley developed one with a leadscrew. It provided controlled，mechanical feed of the tool. This ingenious Englishman also developed a change gear system that could connect the motions of the spindle and leadscrew and thus enable threads to be cut. Lathe Construction. The essential components of a lathe are depicted in the block diagram of picture. These are the bed，headstock assembly，tailstock assembly，carriage assembly，quick-change gearbox，and the leadscrew and feed rod. The bed is the back bone of a lathe. It usually is made of well-normalized or aged gray or nodular cast iron and provides a heavy， rigid frame on which all the other basic components are mounted. Two sets of parallel，longitudinal ways， inner and outer，are contained on the bed，usually on the upper side. 1Some makers use an inverted V-shape for all four ways，whereas others utilize one inverted V and one flat way in one or both sets. Because several other components are mounted and/or move on the ways they must be made with precision to assure accuracy of alignment. Similarly，proper precaution should betaken in operating a lathe to assure that the ways are not damaged. Any inaccuracy in them usually means that the accuracy of the entire lathe is destroyed. The ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion. The headstock is mounted in a fixed position on the inner ways at one end of the lathe bed. It provides a powered means of rotating the work at various speeds. It consists， essentially，of a hollow spindle，mounted in accurate bearings，and a set of transmission gears——similar to a truck transmission——through which the spindle can be rotated at a number of speeds. Most lathes provide from eight to eighteen speeds，usually in a geometric ratio，and on modern lathes all the speeds can be obtained merely by moving from two to four levers. An increasing trend is to provide a continuously variable speed range through electrical or mechanical drives. Because the accuracy of a lathe is greatly dependent on the spindle，it is of heavy construction and mounted in heavy bearings， usually preloaded tapered roller or ball types. A long- itudinal hole extends through the spindle so that long bar stock can be fed through it. The size of this hole is an important size dimension of a lathe because it determines the maximum size of bar stock that can be machined when the material must be fed through the spindle. The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks，face plates，and dog plates on it. 2Whereas small lathes often employ a threaded section to which the chucks are screwed，most large lathes utilize either cam-lock or key-drive taper noses. These provide a large-diameter taper that assures the accurate alignment of the chuck，and a mechanism that permits the chuck or face plate to be locked or unlocked in position without the necessity of having to rotate these heavy attachments.Power is supplied to the spindle by means of an electric motor through a V-belt or silent-chain drive. Most modern lathes have motors of from 5 to15 horsepower to provide adequate power for carbide and ceramic tools at their high cutting speeds.The tailstock assembly consists，essentially，of three parts. A lower casting fits on the inner ways of the bed and can slide longitudinally thereon，with a means for clamping the entire assembly in any desired location. An upper casting fits on the lower one and can be moved transversely upon it on some type of keyed ways. This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapers. The third major component of the assembly is the tailstock quill. This is a hollow steel cylinder，usually about2 to3 inches in diameter， that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw. The open end of the quill hole terminates in a Morse taper in which a lathe center， or various tools such as drills，can be held. A graduated scale， several inches in length，usually is engraved on the outside of the quill to aid in controlling its motion in and out of the upper casting. A locking device permits clamping the quill in any desired position. The carriage assembly provides the means for mounting and moving cutting tools. The carriage is a relatively flat H-shaped casting that rests and moves on 3the outer set of ways on the bed. The transverse bar of the carriage contains ways on which the cross slide is mounted and can be moved by means of a feed screw that is controlled by a small hand wheel and a graduated dial. Through the cross slide a means is provided for moving the lathe tool in the direction normal to the axis of rotation of the work.On most lathes the tool post actually is mounted on a compound rest. This consists of abase，which is mounted on the cross slide so that it can be pivoted about a vertical axis，and an upper casting. The upper casting is mounted on ways on this base so that it can be moved back and forth and controlled by means of a short lead screw operated by a hand wheel and a calibrated dial. Manual and powered motion for the carriage，and powered motion for the cross slide，is provided by mechanisms within the apron，attached to the front of the carriage. Manual movement of the carriage along the bed is effected by turning a hand wheel on the front of the apron，which is geared to a pinion on the back side. This pinion engages a rack that is attached beneath the upper front edge of the bed in an inverted position.To impart powered movement to the carriage and cross slide，a rotating feed rod is provided. The feed rod，which contains a keyway through out most of its length，passes through the two reversing bevel pinions and is keyed to them . Either pinion cam be brought into mesh with a mating bevel gear by means of the reversing lever on the front of the apron and thus provide “forward” or “reverse” power to the carriage. Suitable clutches connect either the rack pinion or the cross-slide screw to provide longitudinal motion of the carriage or transverse motion of cross slide.For cutting threads，a second means of longitudinal drive is provided by a lead screw. Whereas motion of the carriage when driven by the feed-rod 4mechanism takes place through a friction clutch in which slippage is possible，motion through the lead screw is by a direct，mechanical connection between the apron and the lead screw. This is achieved by a split nut. By means of a clamping lever on the front of the apron，the split nut can be closed around the lead screw. With the split nut closed，the carriage is moved along the lead screw by direct drive without possibility of slippage.Modern lathes have a quick-change gear box. The input end of this gearbox is driven from the lathe spindle by means of suitable gearing. The out put end of the gear box is connected to the feed rod and lead screw. Thus，through this gear train， leading from the spindle to the quick-change gearbox，thence to the lead screw and feed rod，and then to the carriage，the cutting tool can be made to move a specific distance，either longitudinally or transversely，for each revolution of the spindle. A typical lathe provides，through the feed rod，forty-eight feeds ranging from 0.002 inch to0.118 inch per revolution of the spindle，and， through the lead screw，leads for cutting forty-eight different threads from 1.5 to 92perinch.On some older and some cheaper lathes，one or two gears in the gear train between the spindle and the change gear box must be changed in order to obtain a full range of threads and feeds.Milling is a basic machining process in which the surface is generated by the progressive formation and removal of chips of material from the workpiece as it is fed to a rotating cutter in a direction perpendicular to the axis of the cutter. .In some cases the workpiece is stationary and the cutter is fed to the work. In most instances a multiple-tooth cutter is used so that the metal removal rate is high，and frequently the desired surface is obtained in a single pass of the work.The tool used in milling is known as a milling cutter. It usually consists of a cylindrical body which rotates on its axis and contains equally spaced peripheral 5teeth that intermittently engage and cut the workpiece. In some cases the teeth extend part way across one or both ends of the cylinder. Because the milling principle provides rapid metal removal and can produce good surface finish，it is particularly well-suited for mass-production work， and excellent milling machines have been developed for this purpose. However，very accurate and versatile milling machines of a general-purpose nature also have been developed that are widely used in job-shop and tool and die work. A shop that is equipped with a milling machine and an engine lathe can machine almost any type of product of suitable size.Types of Milling Operations. Milling operations can be classified into two broad categories，each of which has several variations：1.In peripheral milling a surface is generated by teeth located in the periphery of the cutter body；the surface is parallel with the axis of rotation of the cutter. Both flat and formed surfaces can be produced by this method. The cross section of the resulting surface corresponds to the axial contour of the cutter. This procedure often is called slab milling.1. In face milling the generated flat surface is at right angles to the cutter axis and is the combined result of the actions of the portions of the teeth located on both the periphery and the with the face portions providing a finishing action.The basic concepts of peripheral and face milling are illustrated in Fig. Peripheral milling operations usually are performed on machines having horizontal spindles，whereas face milling is done on both horizontal-and vertical-spindle machines.Surface Generation in Milling. Surfaces can be generated in milling by two distinctly different methods depicted in Fig. Note that in up milling the cutter 6rotates against the direction of feed the workpiece，whereas in down milling the rotation is in the same direction as the feed .As shown in Fig., the method of chip formation is quite different in the two cases. In up milling the c hip is very thin at the beginning, where the tooth first contacts the work，and increases in thickness, be-coming a maximum where the tooth leaves the work. The cutter tends to push the work along and lift it upward from the table. This action tends to eliminate any effect of looseness in the feed screw and nut of the milling machine table and results in a smooth cut. However, the action also tends to loosen the work from the clamping device so that greater clamping forcers must be employed. In addition, the smoothness of the generated surface depends greatly on the sharpness of the cutting edges.In down milling，maximum chip thickness occurs close to the point at which the tooth contacts the work. Because the relative motion tends to pull the workpiece into the cutter，all possibility of looseness in the table feed screw must be eliminated if down milling is to be used. It should never be attempted on machines that are not designed for this type of milling. In as mush as the material yields in approximately a tangential direction at the end of the tooth engagement，there is much less tendency for the machined surface to show tooth marks than when up milling is used. Another consider able advantage of down milling is that the cutting force tends to hold the work against the machine table，permitting lower clamping force to be employed. This is particularly advantageous when milling thin workpiece or when taking heavy cuts.Sometimes a disadvantage of down milling is that the cutter teeth strike against the surface of the work at the beginning of each chip. When the workpiece has a hard surface，such as castings do， this may cause the teeth to dull rapidly.7Milling Cutters. Milling cutters can be classified several ways. One method is to group them into two broad classes，based on tooth relief，as follows：1. Profile-cutters have relief provided on each tooth by grinding a small land back of the cutting edge. The cutting edge may be straight or curved.2.In form or cam-relieved cutters the cross section of each tooth is an eccentric curve behind the cutting edge，thus providing relief. All sections of the eccentric relief，parallel with the cutting edge，must have the same contour as the cutting edge. Cutters of this type are sharpened by grinding only the face of the teeth，with the contour of the cutting edge thus remaining unchanged. Another useful method of classification is according to the method of mounting the cutter. Arbor cutters are those that have a center hole so they can be mounted on an arbor. Shank cutters have either tapered or straight integral shank. Those with tapered shanks can be mounted directly in the milling machine spindle，whereas straight-shank cutters are held in a chuck. Facing cutters usually are bolted to the end of a stub arbor.Types of Milling Cutters. Plain milling cutters are cylindrical or disk-shaped，having straight or helical teeth on the periphery. They are used for milling flat surfaces. This type of operation is called plain or slab milling. Each tooth in a helical cutter engages the work gradually，and usually more than one tooth cuts at a given time. This reduces shock and chattering tendencies and promotes a smoother surface. Consequently，this type of cutter usually is preferred over one with straight teeth. Side milling cutters are similar to plain milling cutters except that the teeth extend radially part way across one or both ends of the cylinder toward the center. The teeth may be either straight or helical. Frequently these cutters are relatively narrow，being disklike in shape. Two or more side milling cutters often are spaced on an arbor to make 8simultaneous，parallel cuts，in an operation called straddle milling. Interlocking slotting cutters consist of two cutters similar to side mills，but made to operate as a unit for milling slots. The two cutters are adjusted to the desired width by inserting shims between them. Staggered-tooth milling cutters are narrow cylindrical cutters having staggered teeth，and with alternate teeth having opposite helix angles. They are ground to cut only on the periphery，but each tooth also has chip clearance ground on the protruding side. These cutters have a free cutting action that makes them particularly effective in milling deep slots. Metal-slitting saws are thin，plain milling cutters，usually from 1/32 to 3/16 inch thick，which have their sides slightly“dished”to provide clearance and prevent binding. They usually have more teeth per inch of diameter than ordinary plain milling cutters and are used for milling deep，narrow slots and for cutting-off operations.9中文譯文車(chē) 床 和 銑 床車(chē)間里擁有一臺(tái)車(chē)床和一臺(tái)普通銑床就能加工出具有適合尺寸的各種產(chǎn)品。用于車(chē)外圓、端面和鏜孔等加工的機(jī)床稱作車(chē)床。車(chē)削很少在其他種類的機(jī)床上進(jìn)行，因?yàn)槠渌麢C(jī)床都不能像車(chē)床那樣方便地進(jìn)行車(chē)削加工。由于車(chē)床除了用于車(chē)外圓外還能用于鏜孔、車(chē)端面、鉆孔和鉸孔，車(chē)床的多功能性可以使工件在一次定位安裝中完成多種加工。這就是在生產(chǎn)中普遍使用各種車(chē)床比其他種類的機(jī)床都要多的原因。兩千多年前就已經(jīng)有了車(chē)床。現(xiàn)代車(chē)床可以追溯到大約 1797 年，那時(shí)亨利 ·莫德斯利發(fā)明了一種具有絲杠的車(chē)床。這種車(chē)床可以控制工具的機(jī)械進(jìn)給。這位聰明的英國(guó)人還發(fā)明了一種把主軸和絲杠相連接的變速裝置，這樣就可以切削螺紋。圖中標(biāo)出了車(chē)床的主要部件：床身、主軸箱組件、尾架組件、拖板組件、變速齒輪箱、絲杠和光杠。床身是車(chē)床的基礎(chǔ)件。它通常是由經(jīng)過(guò)充分正火或時(shí)效處理的灰鑄鐵或者球墨鑄鐵制成，它是一個(gè)堅(jiān)固的剛性框架，所有其他主要部件都安裝在床身上。通常在床身上面有內(nèi)外兩組平行的導(dǎo)軌。一些制造廠生產(chǎn)的四個(gè)條導(dǎo)軌都采用倒“V ”形，而另一些制造廠則將倒“ V ”形導(dǎo)軌和平面導(dǎo)軌相結(jié)合。由于其他的部件要安裝在導(dǎo)軌上并（或）在導(dǎo)軌上移動(dòng)，導(dǎo)軌要經(jīng)過(guò)精密加工，以保證其裝配精度。同樣地，在操作中應(yīng)該小心，以避免損傷導(dǎo)軌。導(dǎo)軌上的任何誤差，常常會(huì)使整個(gè)機(jī)床的精度遭到破壞。大多數(shù)現(xiàn)代車(chē)床的導(dǎo)軌要進(jìn)行表面淬火處理，以減小磨損和擦傷，具有更大的耐磨性。主軸箱安裝在床身一端內(nèi)導(dǎo)軌的固定位置上。它提供動(dòng)力，使工件在各種速度下旋轉(zhuǎn)。它基本上由一個(gè)安裝在精密軸承中的空心主軸和一系列變速齒輪———類似于卡車(chē)變速箱所組成，通過(guò)變速齒輪，主軸可以在許多種轉(zhuǎn)速下旋轉(zhuǎn)。大多數(shù)車(chē)床有 8--18 種轉(zhuǎn)速，10一般按等比級(jí)數(shù)排列。在現(xiàn)代車(chē)床上只需扳動(dòng) 2--4 個(gè)手柄，就能得到全部擋位的轉(zhuǎn)速。目前發(fā)展的趨勢(shì)是通過(guò)電氣的或機(jī)械的裝置進(jìn)行無(wú)級(jí)變速。由于車(chē)床的精度在很大程度上取決于主軸，因此主軸的結(jié)構(gòu)尺寸較大，通常安裝在緊密配合的重型圓錐滾子軸承或球軸承中。主軸中有一個(gè)貫穿全長(zhǎng)的通孔，長(zhǎng)棒料可以通過(guò)該孔送料。主軸孔的大小是車(chē)床的一個(gè)重要尺寸，因?yàn)楫?dāng)工件必須通過(guò)主軸孔供料時(shí)，它確定了能夠加工棒料毛坯的最大外徑尺寸。主軸的內(nèi)端從主軸箱中凸出，其上可以安裝多種卡盤(pán)、花盤(pán)和擋塊。而小型的車(chē)床常帶有螺紋截面供安裝卡盤(pán)之用。很多大車(chē)床使用偏心夾或鍵動(dòng)圓錐軸頭。這些附件組成了一個(gè)大直徑的圓錐體，以保證對(duì)卡盤(pán)進(jìn)行精確地裝配，并且不用旋轉(zhuǎn)這些笨重的附件就可以鎖定或松開(kāi)卡盤(pán)或花盤(pán)。主軸由電動(dòng)機(jī)經(jīng) V 帶或無(wú)聲鏈裝置提供動(dòng)力。大多數(shù)現(xiàn)代車(chē)床都裝有 5--15 馬力的電動(dòng)機(jī)，為硬質(zhì)合金和金屬陶瓷合金刀具提供足夠的動(dòng)力，進(jìn)行高速切削。尾座組件主要由三部分組成。底座與床身的內(nèi)側(cè)導(dǎo)軌配合，并可以在導(dǎo)軌上做縱向移動(dòng)，底座上有一個(gè)可以使整個(gè)尾座組件夾緊在任意位置上的裝置。尾座安裝在底座上，可以沿鍵槽在底座上橫向移動(dòng)，使尾座與主軸箱中的主軸對(duì)中并為切削圓錐體提供方便。尾座組件的第三部分是尾座套筒，它是一個(gè)直徑通常在 2--3 英寸之間的鋼制空心圓柱軸。通過(guò)手輪和螺桿，尾座套筒可以在尾座體中縱向移入和移出幾英寸?；顒?dòng)套筒的開(kāi)口一端具有莫氏錐度，可以用于安裝頂尖或諸如鉆頭之類的各種刀具。通常在活動(dòng)套筒的外表面刻有幾英寸長(zhǎng)的刻度，以控制尾座的前后移動(dòng)。鎖定裝置可以使套筒在所需要的位置上夾緊。拖板組件用于安裝和移動(dòng)切削工具。拖板是一個(gè)相對(duì)平滑的 H 形鑄件，安裝在床身外側(cè)導(dǎo)軌上，并可在上面移動(dòng)。大拖板上有橫向?qū)к墸箼M向拖板可以安裝在上面，并通過(guò)絲杠使其運(yùn)動(dòng)，絲杠由一個(gè)小手柄和刻度盤(pán)控制。橫拖板可以帶動(dòng)刀具垂直于工件的旋轉(zhuǎn)軸線切削。大多數(shù)車(chē)床的刀架安裝在復(fù)式刀座上，刀座上11有底座，底座安裝在橫拖板上，可繞垂直軸和上刀架轉(zhuǎn)動(dòng)。上刀架安裝在底座上，可用手輪和刻度盤(pán)控制一個(gè)短絲杠使其前后移動(dòng)。溜板箱裝在大拖板前面，通過(guò)溜板箱內(nèi)的機(jī)械裝置可以手動(dòng)和動(dòng)力驅(qū)動(dòng)大拖板以及動(dòng)力驅(qū)動(dòng)橫拖板。通過(guò)轉(zhuǎn)動(dòng)溜板箱前的手輪，可以手動(dòng)操作拖板沿床身移動(dòng)。手輪的另一端與溜板箱背面的小齒輪連接，小齒輪與齒條嚙合，齒條倒裝在床身前上邊緣的下面。利用光杠可以將動(dòng)力傳遞給大拖板和橫拖板。光杠上有一個(gè)幾乎貫穿于整個(gè)光杠的鍵槽，光杠通過(guò)兩個(gè)轉(zhuǎn)向相反并用鍵連接的錐齒輪傳遞動(dòng)力。通過(guò)溜板箱前的換向手柄可使嚙合齒輪與其中的一個(gè)錐齒輪嚙合，為大拖板提供“向前”或“向后”的動(dòng)力。適當(dāng)?shù)碾x合器或者與齒條小齒輪連接或者與橫拖板的螺桿連接，使拖板縱向移動(dòng)或使橫拖板橫向移動(dòng)。對(duì)于螺紋加工，絲杠提供了第二種縱向移動(dòng)的方法。光杠通過(guò)摩擦離合器驅(qū)動(dòng)拖板移動(dòng)，離合器可能會(huì)產(chǎn)生打滑現(xiàn)象。而絲杠產(chǎn)生的運(yùn)動(dòng)是通過(guò)溜板箱與絲杠之間的直接機(jī)械連接來(lái)實(shí)現(xiàn)的，對(duì)開(kāi)螺母可以實(shí)現(xiàn)這種連接。通過(guò)溜板箱前面的夾緊手柄可以使對(duì)開(kāi)螺母緊緊包合絲杠。當(dāng)對(duì)開(kāi)螺母閉合時(shí)，可以沿絲杠直接驅(qū)動(dòng)拖板，而不會(huì)出現(xiàn)打滑的可能性。現(xiàn)代車(chē)床有一個(gè)變速齒輪箱，齒輪箱的輸入端由車(chē)床主軸通過(guò)合適的齒輪傳動(dòng)來(lái)驅(qū)動(dòng)。齒輪箱的輸出端與光杠和絲杠連接。主軸就是這樣通過(guò)齒輪傳動(dòng)鏈驅(qū)動(dòng)變速齒輪箱，再帶動(dòng)絲杠和光杠，然后帶動(dòng)拖板，刀具就可以按主軸的轉(zhuǎn)數(shù)縱向地或橫向地精確移動(dòng)。一臺(tái)典型的車(chē)床的主軸每旋轉(zhuǎn)一圈，通過(guò)光杠可以獲得從 0.002 到 0.118 英寸尺寸范圍內(nèi)的 48 種進(jìn)給量；而使用絲杠可以車(chē)削從 1.5 到 92 牙 /英寸范圍內(nèi)的 48 種不同螺紋。一些老式的或價(jià)廉的車(chē)床為了能夠得到所有的進(jìn)給量和加工出所有螺紋，必須更換主軸和變速齒輪箱之間的齒輪系中的一個(gè)或兩個(gè)齒輪。銑削是機(jī)械加工的一個(gè)基礎(chǔ)方法。在這一加工過(guò)程中，當(dāng)工件沿垂直于旋轉(zhuǎn)刀具軸線方向進(jìn)給時(shí)，在工件上形成并去除切屑從而逐漸地銑出表面。12有時(shí)候，工件是固定的，而刀具處于進(jìn)給狀態(tài)。在大多數(shù)情況下，使用多齒刀具，金屬切削量大，只需一次銑削就可以獲得所期望的表面。在銑削加工中使用的刀具稱做銑刀。它通常是一個(gè)繞其軸線旋轉(zhuǎn)并且周邊帶有同間距齒的圓柱體，銑刀齒間歇性接觸并切削工件。在某些情況下，銑刀上的刀齒會(huì)高出圓柱體的一端或兩端。由于銑削切削金屬速度很快，并且能產(chǎn)生良好的表面光潔度，故特別適合大規(guī)模生產(chǎn)加工。為了實(shí)現(xiàn)這一目的，已經(jīng)制造出了質(zhì)量一流的銑床。然而在機(jī)修車(chē)間和工具模具加工中也已經(jīng)廣泛地使用了非常精確的多功能通用的銑床。車(chē)間里擁有一臺(tái)銑床和一臺(tái)普通車(chē)床就能加工出具有適合尺寸的各種產(chǎn)品。銑削操作類型：銑削操作可以分成兩大種類，每一類又有多種類型。1.圓周銑削在圓周銑削中，使用的銑刀刀齒固定在刀體的圓周面上，工件銑削表面與旋轉(zhuǎn)刀具軸線平行，從而加工表面。使用這種方法可以加工出平面和成型表面，加工中表面橫截面與刀具的軸向外輪廓相一致。這種加工過(guò)程常被稱為平面銑削。2.端面銑削銑削平面與刀具的軸線垂直，被加工平面是刀具位于周邊和端面的齒綜合作用形成的。刀具周邊齒完成銑削的主要任務(wù)，而端面齒用于精銑。圓周銑削和端面銑削的基本概念，圓周銑削通常使用臥式銑床，而端銑削則既可在臥式銑床又可以在立式銑床上進(jìn)行。銑削面的形成：銑削時(shí)可以采用兩種完全不同的方法。應(yīng)注意，在逆銑時(shí)，銑刀旋轉(zhuǎn)方向與工件進(jìn)給方向相反，而在順銑時(shí)銑刀旋轉(zhuǎn)與工件進(jìn)給方向相同。在逆銑過(guò)程中，當(dāng)銑刀齒剛切入工件時(shí)，切屑是非常薄的，然后漸漸增厚，在刀齒離開(kāi)工件的地方，切屑最厚。在兩種銑削方法中，切屑的形成是不同的，逆銑過(guò)程中，刀具有推動(dòng)工件并使工件從工作臺(tái)上提升的趨勢(shì)，這種作用有助于消除銑床工作臺(tái)進(jìn)給螺桿和螺母間的間隙，從而形成平穩(wěn)的切削。然而，這種作用也有造成工件與夾緊裝置之間的松動(dòng)的趨勢(shì)，這時(shí)應(yīng)施加更大的夾緊力。此外，銑削表面的平整度主要取決于切削刃的鋒利程度。順銑時(shí)，13最大切屑厚度產(chǎn)生于靠近刀具與工件接觸點(diǎn)處。由于相對(duì)運(yùn)動(dòng)趨于把工件拉向銑刀，如果采用順銑法，要消除工作臺(tái)進(jìn)給螺桿可能產(chǎn)生的松動(dòng)。因此，對(duì)于不能用于順銑的銑床，不要采用順銑方法。因?yàn)樵阢姷督Y(jié)束切削時(shí)，處于切線方向的被切材料發(fā)生屈服，所以與逆銑相比，順銑的被加工表面沒(méi)有什么切痕。順銑的另一個(gè)優(yōu)勢(shì)是切削力趨于將工件壓緊在工作臺(tái)上，因此對(duì)工件的夾緊力可以小于逆銑。這一優(yōu)勢(shì)可以用于銑削較薄的工件或進(jìn)行強(qiáng)力切削。順銑的弱點(diǎn)是銑刀齒剛一切削每片鐵屑時(shí)，刀齒會(huì)撞擊工件的表面。如果工件表面堅(jiān)硬，像鑄件，就會(huì)使刀齒迅速地變鈍。銑刀分類有多種方法，一種方法是根據(jù)刀具后角將銑刀分為兩大類：1.仿形銑刀 每個(gè)刀齒在切削刃的背面磨了一個(gè)很小的棱面形成后角，切削刃可以是直線或曲線的。2.成形或凸輪形后角銑刀 每個(gè)齒的橫截面在切削刃的背面呈偏心曲線狀，以產(chǎn)生后角。偏心后角的各面與切削刃平行，具有切削刃的相同形狀。這種類型的銑刀僅需磨削齒的前刀面就可以變得鋒利，只要切削刃的外形保持不變。銑刀的另一種分類方法是根據(jù)銑刀安裝的方法進(jìn)行分類。心軸銑刀帶有一個(gè)中心孔以使銑刀安裝在心軸上。帶柄銑刀有一錐柄或直柄軸，含錐形軸柄的銑刀可以直接安裝在銑床的主軸上，而直柄軸的銑刀則是夾持在卡盤(pán)里。平面銑刀通常用螺栓固定在刀軸的末端上。根據(jù)這種分類方法，通用型的銑刀可分類如下：心軸銑刀：圓柱形銑刀，角度銑刀，側(cè)刃銑刀，嵌齒銑刀，錯(cuò)齒銑刀，成形銑刀 ，開(kāi)槽銑刀，高速切削刀。帶柄銑刀：端面銑刀，T 形槽銑刀，整體式銑刀，半圓鍵座銑刀，套式銑刀，高速切削刀，空心銑刀。銑刀的類型圓柱形銑刀是在圓周上有直的或螺旋形的齒的圓柱形或盤(pán)形銑刀。它們可以用來(lái)銑削平面，這種銑削稱做平面銑削。螺旋形的銑刀上的每個(gè)齒是逐漸地接觸工件，在給定的時(shí)間內(nèi)，一般有多齒進(jìn)行銑削，這樣可以減少震動(dòng)，獲得一個(gè)較平滑的表面。因此，與直齒銑刀相比，這種類型的銑刀，通常使用得更多。側(cè)刃銑刀的齒除了在圓柱刀體的一端或兩端向徑向延伸之外，與圓柱形銑14刀是相似的。側(cè)刃銑刀的刀齒既可以是直線的，也可以是螺旋形的，這種銑刀一般較窄小，具有盤(pán)形的形狀。在跨式銑削加工中，常常將兩個(gè)或更多的側(cè)刃銑刀同時(shí)相間地安裝在一個(gè)刀桿上同步并行切削。雙聯(lián)槽銑刀是由兩個(gè)側(cè)刃銑刀組成，但是在銑槽時(shí)，作為一組銑刀進(jìn)行操作。在兩個(gè)銑刀之間添加一些薄墊片，以調(diào)整之間的間距。錯(cuò)齒銑刀是較薄的圓柱形銑刀，刀上有相互交錯(cuò)的刀齒，相鄰刀齒具有相反的螺旋角。這種銑刀經(jīng)研磨后僅用于周銑，在每個(gè)齒突出的一邊，留有供切屑排出的縫隙。這種類型的銑刀可用于高速切削，在銑削深槽時(shí)可以發(fā)揮獨(dú)特的作用。開(kāi)槽銑刀是一種薄型的圓柱形銑刀