LATHE
词性转换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. Becau lathe can do boring, facing, drilling, and reaming in addition to turning, their versatility permits veral operations to be performed with a single tup of the work place. The accounts for the fact that lathes of various types are more widely ud in manufacturing than any other machine tool.
Lathes in various forms have existed for more than two thousand years. Modem lathes date from about 1797, when Henry Maudsley developed one with a lea crew. 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 lea crew and thus enable threads to be cut.
Lathe Construction. The esntial components of a lathe are depicted in the block diagram. The are the bed, headstock asmbly, tailstock asmbly, carriage asmbly, quick-change gear box, and the lea crew and feed rod.
The bed is the backbone 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 ts 石家庄法语培训
of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers u an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both ts. Becau veral 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 be taken 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 modem 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, esntially, of a hollow spindle, mounted in accurate bearings? And a t 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 modem 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.
Becau 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 longitudinal 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 becau it de
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terminus the maximum size of bar stock that can be machined when the material must be fed through the spinale.
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. Whereas small lathes often employ a threaded ction to which the chucks are screwed, most large lathes utilize either cam-lock or key-drive taper nos. The 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 the heavy attachments.
Power is supplied to the spindle by means of an electric motor through a V-belt or silent-chain drive. Most modem lathes have motors of from 5 to15 horpower to provide adequate power for carbide and ceramic tools at their high cutting speeds.灰姑娘的动画片>go right ahead
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The tailstock asmbly consists, esntially, 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 asmbly in any desired location. An upper casting fits on the lower one and can be moved transverly upon it on some type of keyed ways. This transver motion pemfits aligning the tailstock and headstock spindles and provides a method of tuming tapers. The third major component of the asmbly is the tailstock quill. This is a hollow steel cylinder, usually about 2 to sinches in diameter, that can be moved veral inches longitudinally in and out of the upper casting by means of a handwheel and screw. The open end of the quill hole terminates in a mor. Taper in which a lathe center, or various tools such as drills, can be held. A graduated scale, veral 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 asmbly provides the means for mounting and moving cutting tools. The carriage is a reianvely fiat H-shaped casting that rests and moves on the outer t of ways on the bed. The transver 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 handwheel 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 a ba, 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 ba .so that it can be moved back and forth and controlled by means of a short lead screw operated by a handwheel 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 handwheel 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 throughout most of its length, pass 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 "rever" pow
er to the carriage. Suitable clutches connect either the rack pinion or the cross-shde screw to provide longitudinal motion of the carriage or transver motion of cross slide.
For cutting threads, a cond means of longitudinal drive is provided by a lead screw. Whereas motion of the carriage when driven by the feed-rod mechanism takes place through a friction clutch in which shppage is possible, motion through the lead screw is by a direct, mechanical connection between the apron and the lead screw, s This is achieved by a split nut. By means of a clamping lever on the front of the
lost riverapron, the split nut can be clod around the lead screw. With the split nut clod, 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 gear box is driven from the lathe spindle by means of suitable gearing. The output 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 gear box, 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 transverly, for each revolution of the spindle.
A typical lathe provides, through the feed rod, forty-eight feeds ranging from 0.002 inch to 0.118 inch
per revolution of the spindle, and, through tne lead screw, leads for cutting forty-eight different threads from 1.5 to 92 per inch. 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.
车床
用与车外圆、端面和镗孔等加工的机床叫车床。车削很少在其他种类的机床上进行，因为其他机床都不能像车床那样方便地进行车削加工。由于车床除了用于车外圆外还能用于镗孔、车端面、钻孔和铰孔，车床的多功能性可以使工件在一次定位安装中完成多种加工。这就是在生产中普遍使用各种车床比其他种类的机床都要多的原因。
两千多年前就已经有了车床。现代车床可以追溯到大约17刃年，那时亨利·莫德斯利发明了一种具有丝杠的车床。这种车床可以控制工具的机械进给。这位聪明的英国人还发明了一种把主轴和丝杠相连接的变速装置，这样就可以切削螺纹。
车床的主要部件：床身、主轴箱组件、尾架组件、拖板组件、变速齿轮箱、丝杠和光杠
床身是车床的基础件。它通常是由经过充分正火或时效处理的灰铸铁或者球墨铸铁制成，它是一个坚
固的刚性框架，所有其他主要部件都安装在床身上。通常在床身上面有内外两组平行的导轨。一些制造厂生产的四个条导轨都采用倒“V”形，而另一些制造厂则将倒“V”形导轨和平面导轨相结合。由于其他的部件要安装在导轨上并(或)在导轨上移动，导轨要经过精密加工，以保证其装配精度。同样地，在操作中应该小心，以避免损伤导轨。导轨上的任何误差，常常会使整个机床的精度遭到破坏。大多数现代车床的导轨要进行表面淬火处理，以减小磨损和擦伤，具有更大的耐磨性。主轴箱安装在床身一端内导轨的固定位置上。它提供动力，使工件在各种速度下旋转。它基本上由一个安装在精密轴承中的空心主轴和一系列变速齿轮——类似于卡车变速箱所组成，通过变速齿轮，主轴可以在许多种转速下旋转。大多数车床有8—18种转速，一般按等比级数排列。在现代车床上只需扳动2～4个手柄，就能得到全部挡位的转速。目前发展的趋势是通过电气的或机械的装置进行无级变速。
由于车床的精度在很大程度上取决于主轴，因此主轴的结构尺寸较大，通常安装在紧密配合的重型圆锥滚子轴承或球轴承中。主轴中有一个贯穿全长的通孔，长棒料可以通过该孔送料。主轴孔的大小是车床的一个重要尺寸，因为当工件必须通过主轴孔供料时，它确定了能够加工棒料毛坯的最大外径尺寸。肥皂剧英文
主轴的内端从主轴箱中凸出，其上可以安装多种卡盘、花盘和挡块。而小型的车床常带有螺纹截面供安装卡盘之用。很多大车床使用偏心夹或键动圆锥轴头。这些附件组成了一个大直径的圆锥体，以保证对卡盘进行精确地装配，并且不用旋转这些笨重的附件就可以锁定或松开卡盘或花盘。
