?Drilling and Drills
钻削和钻头
Drilling involves producing through or blind holes in a workpiece by forcing a tool, which rotates around its axis, against the workpiece.
钻削就是通过迫使绕自身轴线旋转的切削刀具进入工件而在其上生成通孔或盲孔。
Consequently, the range of cutting from that axis of rotation is equal to the radius of the required hole. In practice, two symmetrical cutting edges that rotate about the same axis are employed.
因此，从旋转轴线开始的切削范围等于所需孔的半径。实际上，使用的是两条围绕相同轴线旋转的对称切削刃。
Drilling operations can be carried out by using either hand drills or drilling machines. The latter differ in size and construction. Nevertheless, the tool always rotates around its axis while the workpiece is kept firmly fixed. This is contrary to drilling on a lathe.
钻削作业既能采用手钻也能采用钻床来实现。钻床在尺寸和结构上虽有差别，然而始终都是切削刀具围绕自身轴线旋转、工件稳固定位的形式。这正好与在车床上钻孔相反。
Cutting Tool for Drilling Operation
In drilling operations, a cylindrical rotary-end cutting tool, called a drill, is employed. The drill can have either one or more cutting edges and corresponding flutes, which can be straight or helical.
用于钻削作业的切削刀具
在钻削作业中，要用到被称为钻头的圆柱形回转端切削刀具。钻头可以有一条或多条直的或是螺旋状的切削刃以及相应的出屑槽。
The function of the flutes is to provide outlet passages for the chips generated during the drilling operation and also to allow lubricants and coolants to reach the cutting edges and the surface being machined. Following is a survey of the commonly used drills.
出屑槽的功能是给钻削作业中产生的切屑提供排出通道，并允许润滑剂和冷却液到达切削刃和正在被加工的表面。下面是常用钻头的概述。
Twist drill. The twist drill is the most common type of drill. It has two cutting edges and two helical flutes that continue over the length of the drill body, as shown in Fig.12.1. The drill also consists of a neck and a shank that can be either straight or tapered.
麻花钻：麻花钻是最常用的钻头类型。它有两条切削刃和两条沿钻头体全长连续的螺旋状出屑槽，如图12.1所示。麻花钻还包括钻颈和钻柄，钻柄可以是直的也可以是锥形的。
In the latter case, the shank is fitted by the wedge action into the tapered socket of the spindle and has a tang, which goes into a slot in the spindle socket, thus acting as a solid means for transmitting rotation.
锥形钻柄通过楔入动作安装在主轴的锥形轴孔中，钻柄上还有柄舌插入主轴轴孔中的插槽，从而作为传递转动的可靠方法。
On the other hand, straight-shank drills are held in a drill chuck that is, in turn, fitted into the spindle socket in the same way as tapered shank drills.
另一方面，直柄钻头用钻头卡盘夹住，接下来钻头卡盘则象锥形钻柄钻头一样安装在主轴轴孔内。
As can be seen in Fig.12.1, the two cutting edges are referred to as the lips, and are connected together by a wedge, which is a chisel-like edge. The twist drill also has two margins, which enable proper guidance and locating of the drill while it is in operation.
如图12.1所示，两条切削刃就是钻唇，通过凿子状边缘的楔形体连在一起。麻花钻还有两条导向边，用于作业中钻头的正确导向和定位。
The tool point angle (TPA) is formed by the two lips and is chosen based on the properties of the material to be cut. The usual TPA for commercial drills is 118°, which is appropriate for drilling low-carbon steels and cast irons.
两条钻唇形成钻顶角，并根据被钻削材料的性能来选取其大小。商品化钻头的钻顶角一般为118°，这适用于钻削低碳钢和铸铁。
For harder and tougher metals, such as hardened steel, brass and bronze, larger TPAs (130°or 140°) give better performance. The helix angle of the flutes of the commonly used twist drills ranges between 24°and 30°. When drilling copper or soft plastics, higher values for the helix angle are recommended (between 35°and 45°).
对于更硬更韧的金属，诸如淬火钢、黄铜和青铜，更大的钻顶角(130°或140°)才能有更好的效果。麻花钻常用的出屑槽螺旋角范围为24°到 30°。钻削紫铜或软塑料时，推荐采用更大的
螺旋角(35°到45°)。
Twist drills are usually made of high-speed steel, although carbide-tipped drills are also available. The sizes of twist drills used in industrial practice range from 0.01 up to 3.25 in. (i. e., 0.25 up to 80 mm).
虽然也有硬质合金刀尖的钻头，麻花钻一般用高速钢制成。工业实际中使用的麻花钻尺寸范围为0.01到3.25英寸(即0.25到80毫米)。
Core drills. A core drill consists of the chamfer, body, neck, and shank, as shown in Fig.12.2. This type of drill may have either three or four flutes and equal number of margins, which ensure superior guidance, thus resulting in high machining accuracy.
空心钻：空心钻包括斜面、钻头体、钻颈和钻柄，如图12.2所示。这类钻头可以有三条或四条出屑槽及相同数量的保证良好导向的导向边，这样使得加工有高精度。
It can also be seen in Fig.12.2 that a core drill has flat end. The chamfer can have
three or four cutting edges or lips, and the lip angle may vary between 90°and 120°. 在图12.2中同样能看到，空心钻具有平坦的端部。斜面可以有三或四条切削刃或钻唇，并且钻唇角可以在90°到120°之间变化。
Core drills are employed for enlarging previously made holes and not for originating holes. This type of drill is characterized by greater productivity, high machining accuracy, and superior quality of the drilled surfaces.
空心钻用于扩大已有的孔而不是打孔。这类钻头具有较大生产率、高加工精度和优良钻削表面质量的特性。
Gun drills. Gun drills are used for drilling deep holes. All gun drills are straight-fluted, and each has a single cutting edge. A hole in the body acts as a conduit to transmit coolant under considerable pressure to the tip of the drill.
深孔钻：深孔钻用于钻深孔。所有深孔钻都是直出屑槽的，并且均为单切削刃。钻头体中有个孔作为导管在相当大的压力下将冷却液传送到钻头顶端。
There are two kinds of gun drills, namely, the center-cut gun drill used for drilling blind holes and the trepanning drill. The latter has a cylindrical groove at its center, thus generating a solid core, which guides the tool as it proceeds during the drilling operation.
深孔钻有两种类型，即用于钻盲孔的中心切削深孔钻和套孔钻。后者在其中心有一圆
柱形沟槽，这样能生成整体芯在钻孔作业过程中引导钻头。
Spade drills. Spade drills are used for drilling large holes of 3.5 in.(90mm) or more. Their design results in a marked saving in cost of the tool as well as a tangible reduction in its weight, which facilitates its handling. Moreover, this type of drill is easy to grind.
扁平钻：扁平钻用于钻削3.5英寸(90毫米)或更大的大孔。其设计使得钻头成本明显节省、重量切实减轻，重量轻又使操作更方便。此外这种钻头容易磨利。
?Milling and Milling Cutter
铣削和铣刀
Milling is a machining process that is carried out by means of a multiedge rotating tool known as a milling cutter.
铣削是采用被称为铣刀的多刃旋转刀具完成的机加工作业。
In this process, metal removal is achieved through combining the rotary motion of the milling cutter and linear motions of the workpiece simultaneously. Milling operations are employed in producing flat, contoured and helical surfaces as well as for thread- and gear-cutting operation.
在此工艺中，金属去除是通过铣刀的旋转运动和工件的直线运动的组合实现的。铣削作业既可用于生成平面、轮廓面和螺旋面，也可用于切削螺纹和齿轮。
Each of the cutting edges of a milling cutter acts as an individual
single-point cutter when it engages with the workpiece metal. Therefore, each of those cutting edges has appropriate rake and relief angles.
在铣刀切削工件金属时，铣刀的每条切削刃都象一单独的单刃刀具一样作用。所以每条切削刃都适当的前后角。
Since only a few of the cutting edges are engaged with the workpiece at a time, heavy cuts can be taken without adversely affecting the tool life. In fact, the permissible cutting speeds and feeds for milling are three to four times higher than those for turning or drilling.
由于同一时间只有部分切削刃切削工件，因此可以在对刀具寿命没有不利影响的情况下承担重型切削。事实上，铣削允许的切削速度和进给比车削或钻削高三到四倍。
Moreover, the quality of the surfaces machined by milling is generally superior to the quality of surfaces machined by turning, shaping, or drilling.
此外，由铣削加工的表面质量通常优于车削、刨削或钻削加工的表面质量。
A wide variety of milling cutters is available in industry. This, together
with the fact that a milling machine is a very versatile machine tool, makes the milling machine the backbone of a machining workshop.
工业上可采用的铣刀类型众多。连同铣床是极通用机床的事实，使得铣床成为机加工车间的支柱。
As far as the direction of cutter rotation and workpiece feed are concerned, milling is performed by either of the following two methods.
至于涉及到铣刀转动的方向和工件的进给，铣削可以通过下列两种方法之一进行。
Up milling (conventional milling). In up milling the workpiece is fed against the direction of cutter rotation, as shown in Fig.12.3a. As we can see in that figure, the depth of cut (and consequently the load) gradually increases on the successively engaged cutting edges.
逆铣(传统铣削)：在逆铣中，工件逆着铣刀转动的方向进给，如图12.3a所示。就像在此图中能看到的那样，切削深度(及作为结果的载荷)随着切削刃持续进入切削而逐渐增加。
Therefore, the machining process involves no impact loading, thus ensuring smoother operation of the machine tool and longer tool life. The quality of the machined surface obtained by up milling is not very high. Nevertheless, up milling is commonly used in industry, especially for rough cuts.
所以，这种工艺没有冲击载荷，从而保证了机床的较平稳运行和较长寿命。通过逆铣所得机加工表面质量不是很高。然而逆铣仍经常被用在工业上，尤其是粗切削时。
Down milling (climb milling). As can be seen in Fig.12.3b, in down milling the cutter rotation coincides with the direction of feed at the contact point between the tool and the workpiece. It can also be seen that the maximum depth of cut is achieved directly as the cutter engages with the workpiece.
顺铣(同向铣削)：如同在图12.3b中看到的那样，在顺铣时刀具与工件之间接触点上铣刀旋转与进给方向一致。还可以看到当刀具进入工件切削时直接达到最大切削深度。
This results in a kind of impact, or sudden loading. Therefore, this method cannot be used unless the milling machine is equipped with a backlash eliminator on the feed screw. The advantages of this method include higher quality of the machined surface and easier clamping of workpieces, since the cutting forces act downward.
这会导致一种冲击，或突然加载。因此，这种方法只有当铣床在进给螺栓上配备间隙消除器时才采用。这种方法的优点包括机加工表面质量较高和工件由于切削力向下作用而较容易夹紧。
Types of Milling Cutters
There is a wide variety of milling cutter shapes. Each of them is designed to perform effectively a specific milling operation.
铣刀的类型
铣刀的形状类型很多。其中每种都是为有效进行特定的铣削作业而设计的。
Generally, a milling cutter can be described as a multiedge cutting tool having the shape of a solid of revolution, with the cutting teeth arranged either on the periphery or on an end face or on both. Following is a quick survey of the commonly used types of milling cutters.
通常，铣刀可以被描述为具有旋转实体形状并将切削齿安装在周边或一到两个端面上的多刃切削刀具。下面是常用铣刀类型的快速综览。
Plain milling cutter. A plain milling cutter is a disk-shaped cutting tool that may have either straight or helical teeth, as shown in Fig.12.4a. This type is always mounted on horizontal milling machines and is used for machining flat surfaces.
平面铣刀：平面铣刀是一种盘状切削刀具，它可以具有直齿或螺旋齿，如图12.4a所示。这类铣刀总是安装在卧式铣床上，用于机加工平面。
Face milling cutter. A face milling cutter is also used for machining flat surfaces. It is bolted at the end of a short arbor, which is in turn mounted on a vertical milling machine. Fig.12.4b indicates a milling cutter of this type.
端面铣刀：端面铣刀也可用于机加工平面。它用螺栓固定在短刀杆的端部，而短刀杆则依次安装于立式铣床上。图12.4b显示了这类铣刀。
Plain metal slitting saw cutter. Fig.12.4c indicates a plain metal slitting saw cutter. we can see that it actually involves a very thin plain milling cutter.
平面金属开槽锯刃铣刀：图12.4c显示了一种平面金属开槽锯刃铣刀。可以看到它其实是一种很薄的平面铣刀。
Side milling cutter. A side milling cutter is used for cutting slots, grooves, and splines. As shown in Fig.12.4d, it is quite similar to the plain milling cutter, the difference being that this type has teeth on the sides. As is the case with the plain cutter, the cutting teeth can be straight or helical.
侧铣刀：侧铣刀用于切削狭槽、凹槽和花键槽。正如图12.4d所示，它与平面铣刀十分相似，差别在于此类铣刀齿在侧面。象平面铣刀的情况一样，切削齿既可以是直的也可以是螺旋的。
Angle milling cutter. An angle milling cutter is employed in cutting dovetail
grooves, ratchet wheels, and the like. Fig.12.4e indicates a milling cutter of this type.
倾斜铣刀：倾斜铣刀用于切削燕尾槽、棘轮之类的。图12.4e显示了这类铣刀。
T-slot cutter. As shown in Fig.12.4f, a T-slot cutter involves a plain milling cutter with an integral shaft normal to it. As the name suggests, this type is used for milling T-slots.
T型槽铣刀：如图12.4f所示，T型槽铣刀包括了一个平面铣刀和一根垂直于它的整体轴。正像其名字所表明的，这类铣刀用于铣削T型槽。
End mill cutter. End mill cutters find common applications in cutting slots, grooves, flutes, splines, pocketing work, and the like. Fig.12.4g indicates an end mill cutter. The latter is always mounted on a vertical milling machine and can have two or four flutes, which may be either straight or helical.
端面铣刀：端面铣刀在切削狭槽、凹槽、长凹槽、花键槽、凹状工件之类时均能发现其普遍应用。图12.4g为端面铣刀。它总是安装在立式铣床上，并具有两到四条既可是直的也可是螺旋的长凹槽。
Form milling cutter. The teeth of a form milling cutter have a certain shape, which is identical to the section of the metal to be removed during the milling operation. Examples of this type include gear cutters, gear hobs, convex and concave cutters, and the like. From milling cutters are mounted on horizontal milling machines.
成形铣刀：成形铣刀的齿具有特定的形状，这个形状与铣削时要切削的那部分金属的形状一致。这类铣刀的例子包括齿轮铣刀、齿轮滚刀、凸形和凹形铣刀等等。成形铣刀安装在卧式铣床上。
Materials of Milling Cutters
The commonly used milling cutters are made of high-speed steel, which is generally adequate for most jobs.
铣刀的材料
普通使用的铣刀用高速钢制造，这对一般大多数工作已足够。
Milling cutters tipped with sintered carbides or cast nonferrous alloys as cutting teeth are usually employed for mass production, where heavier cuts and/or high cutting speeds are required.
对大规模生产而言，因为其需要重型切削和/或高切削速度，铣刀顶端常装有烧结碳化物或有
色金属碳合金作为切削齿。
第十四单元
?Dimensioning 标注尺寸
The design of a machine includes many factors other than those of determining the loads and stresses and selecting the proper materials.
机械设计除了计算载荷和应力、选择合适的材料外，还包括许多其它因素。
Before construction or manufacture can begin, it is necessary to have complete assembly and detail drawings to convey all necessary information to the shop men. The designer frequently is called upon to check the drawings before they are sent to the shop. Much experience and familiarity with manufacturing processes are needed before one can become conversant with all phases of production drawings.
在建造或制造开始前，完成装配图和零件图以把必要信息传达给车间工人是必须的。在送往车间前设计者常常被召集来检查图纸。而在精通生产图纸的所有情况之前，需要有许多经验并熟悉制造工艺。
Drawings should be carefully checked to see that the dimensioning is done in a manner that will be most convenient and understandable to the production departments. It is obvious that a drawing should be made in such a way that it has one and only one interpretation.
图纸必须仔细检查其尺寸是否按生产部门最方便易懂的方式标注。很明显图纸应该只有唯一的解释。
In particular, shop personnel should not be required to make trigonometric or other involved calculations before the production machines can be set up.
Dimensioning is an involved subject and long experience is required for its mastery.
尤其是不能要求车间工人在生产机械安排前进行三角或其它复杂的计算。
尺寸标注是一项复杂的工作，要掌握它需要有丰富的经验。
Tolerances must be placed on the dimensions of a drawing to limit the permissible variations in size because it is impossible to manufacture a part exactly to a given dimension.
由于要把零件加工到正好为给定尺寸是不可能的，因此图纸的尺寸必须加上公差以限制其可允许的变化。
Although small tolerances give higher quality work and a better operating mechanism, the cost of manufacture increases rapidly as the tolerances are reduced, as indicated by the typical curve of Fig14.1. It is therefore important that the tolerances be specified at the largest values that the operating or functional considerations permit.
虽然较小公差能得到较高加工质量和较好操作机构，但随着公差的减小制造成本会迅速增加，如图14.1的典型曲线所示。因此公差被定为从操作或功能考虑允许的最大值是重要的。
Tolerances may be either unilateral or bilateral. In unilateral dimensioning, one tolerance is zero, and all the variations are given by the other tolerance. In bilateral dimensioning, a mean dimension is used which extends to the midpoint of the tolerance zone with equal plus and minus variations extending each way from this dimension.
公差既可以是单向的也可以是双向的。单向标注有一公差为零，所有变化都由另一公差给定。而双向标注则采用一平均尺寸，它将公差带中点从该尺寸双向扩展为相等的正负变化范围。
The development of production processes for large-volume manufacture at low cost has been largely dependent upon interchangeability of component parts. Thus the designer must determine both the proper tolerances for the individual parts, and the correct amount of clearance or interference to permit assembly with the mating parts.
大规模低成本制造生产工艺的发展很大程度取决于组成零件的互换性。因此设计者必须确定单个零件的合适公差以及配合零件装配允许的正确间隙或过盈量。
The manner of placing tolerances on drawings depends somewhat on the kind of product or type of manufacturing process. If the tolerance on a dimension is not specifically stated, the drawing should contain a blanket note which gives the value of the tolerance for such dimensions.
在图纸上标注公差的方法相当程度上依赖于产品的性质或制造工艺的类型。如果尺寸公差没有特别注明，图纸应该包含一个给出这些尺寸公差值的普遍适用注释。
However, some companies do not use blanket notes on the supposition that if each dimension is considered individually, wider tolerances than those called for in the note could probably be specified. In any event it is very important that a drawing be free from ambiguities and be subject only to a single interpretation.
然而有些公司不采用普遍适用注释，假定每个尺寸是单独被考虑的，可能会规定出比注释中要求的更宽的公差。在任何情况下图纸不模棱两可并只服从于单一的解释是十分重要的。
?Dimension and Tolerance
尺寸和公差
In dimensioning a drawing, the numbers placed in the dimension lines represent dimension that are only approximate and do not represent any degree of accuracy unless so stated by the designer.
在图纸标注尺寸时，除非设计者有意标明，注在尺寸线上的数字代表的尺寸仅仅是近似的，并不代表任何精度等级。
To specify a degree of accuracy, it is necessary to add tolerance figures to the dimension. Tolerance is the amount of variation permitted in the part or the total variation allowed in a given dimension.
为了详细标明精度等级，有必要在尺寸上增加公差数字。公差是零件允许的变动量或给定尺寸允许的总变动。
A shaft might have a nominal size of 2.5in.(63.5mm), but for practical reasons this figure could not be maintained in manufacturing without great cost. Hence, a certain
tolerance would be added and, if a variation of±0.003in.(±0.08mm) could be permitted, the dimension would be stated 2.500±0.003(63.5±0.08mm).
一根轴可能的名义尺寸为2.5in.(63.5mm)，但由于实际原因不用大成本是不能在制造中保持这个数字的，因此要增加确定的公差。如果允许有±0.003in.(±0.08mm)的变化，则此尺寸可表达为2.500±0.003(63.5±0.08mm)。
Dimensions given close tolerances mean that the part must fit properly with some other part. Both must be given tolerances in keeping with the allowance desired, the manufacturing processes available, and the minimum cost of production and assembly that will maximize profit.
具有紧密公差的尺寸表示该零件必须恰当地与某些其它零件配合。所采用的制造工艺和使利润最大化的最小生产及装配成本都要求给定公差以保持所需允差。
Generally speaking, the cost of a part goes up as the tolerance is decreased. If a part has several or more surfaces to be machined, the cost can be excessive when little deviation is allowed from the nominal size.
一般而言，零件的成本随着公差的减小而上升。如果一个零件有若干或较多表面要机加工，且几乎不允许偏离名义尺寸，则成本会超过正常合理的界限。
Allowance, which is sometimes confused with tolerance, has an altogether different meaning. It is the minimum clearance space intended between mating parts
and represents the condition of tightest permissible fit.
允差，有时会跟公差混淆，但其具有完全不同的含义。它是配合零件之间最小的预期间隙空间，代表着允许的最紧配合条件。
, is to fit a hole of size 1.500+0.003, the minimum size hole If a shaft, size 1.498
-0.003
is 1.500 and the maximum size shaft is 1.498. Thus the allowance is 0.002 and the maximum clearance is 0.008 as based on the minimum shaft size and maximum hole dimension.
如果一根尺寸为1.498-0.003的轴与尺寸为1.500+0.003的孔配合，孔的最小尺寸为1.500而轴的最大尺寸为1.498。这样允差就是0.002，而由最小轴尺寸和最大孔尺寸形成的最大间隙为0.008。
Tolerances may be either unilateral or bilateral. Unilateral tolerance means that any variation is made in only one direction from the nominal or basic dimension. Referring to the previous example, the hole is dimensioned 1.500+0.003, which represents a unilateral tolerance.
公差可以是单向的也可以是双向的。单向公差意味着任何变动都是只从名义或基本尺寸出发向一个方向变动的。引用前例，孔的尺寸标注为1.500+0.003，它表示了一个单向公差。If the dimensions were given as 1.500±0.003, the tolerance would be bilateral; that is, it would vary both over and under the nominal dimension. The unilateral system permits changing the tolerance while still retaining the same allowance or type of fit.
如果尺寸标为1.500±0.003，就是双向公差；即它可以在名义尺寸之上或之下变化。单向体系允许在依然保留相同允差或配合类型的情况下改变公差。
With the bilateral system, this is not possible without also changing the nominal size dimension of one or both of the two mating parts. In mass production, where mating parts must be interchangeable, unilateral tolerances are customary. To have an interference or force fit between mating parts, the tolerances must be such as to create a zero or negative allowance.
而双向体系在不同时改变一个或两个配合零件名义尺寸的情况下，这是不可能做到的。大规模生产中配合零件必须能互换，单向公差是经常遇到的。为了使配合零件之间具有过盈或强制配合，公差必须产生零或负允差。
?Tolerances, Limits and Fits
公差、极限和配合
The drawing must be a true and complete statement of the designer’s requirements expressed in such a way that the part is convenient to manufacture.
图纸必须按方便制造零件的方式将设计者的要求真实和完整地表达出来。
Every dimension necessary to define the product must be stated once only and not repeated in different views. Dimensions relating to one particular feature, such as the position and size of a hole, should, where possible, appear on the same view.
对每一描述产品所需的尺寸都只须标注一次而不必在不同的视图中重复。有关同一特性的尺寸，诸如孔的位置和大小，如果可能应出现在同一视图上
There should be no more dimensions than are absolutely necessary, and no feature should be located by more than one dimension in any direction.
除绝对需要的尺寸外，不应该有更多的尺寸；而在任意方向上，只能在一个尺寸上标注特性要求。
It may be necessary occasionally to give an auxiliary dimension for reference, possibly for inspection. When this is so, the dimension should be enclosed in a bracket and marked for reference. Such dimensions are not governed by general tolerances.
偶尔也可能为了检查而必须给出供参考的辅助尺寸。在这种情况下，尺寸应该用括号括起来，以便参考。这样的尺寸不受通用公差控制。
Dimensions that affect the function of the part should always be specified and not left as the sum or difference of other dimensions.
影响零件功能的尺寸总是应该标注的而不要留作其它尺寸的和或差。
If this is not done, the total permissible variation on that dimension will form the sum or difference of the other dimensions and their tolerances, and this will result in these tolerances having to be made unnecessarily tight. The overall dimension should always appear.
如果不是这样，那尺寸允许的总的变化将形成其它尺寸及它们的公差的和或差，这会导致这些公差不得不定得过紧。总尺寸一般应该标注。
All dimensions must be governed by the general tolerance on the drawing unless otherwise stated. Usually, such a tolerance will be governed by the magnitude of the dimension. Specific tolerances must always be stated on dimensions affecting function or interchangeability.
除非另行说明，所有尺寸都必须受图上的通用公差控制。一般这样的公差受到尺寸量
值的控制。在影响功能或互换性的尺寸上必须标注专门的公差。
A system of tolerances is necessary to allow for the variations in accuracy that are bound to occur during manufacture, and still provide for interchangeability and correct function of the part.
为了允许在制造过程中必然会发生的精度变化，并提供零件的互换性和正确功能，一个公差系统是必需的。
A tolerance is the difference in a dimension in order to allow for unavoidable imperfections in workmanship. The tolerance range will depend on the accuracy of the manufacturing organisation, the machining process and the magnitude of the dimension.
公差是为了允许工艺上不可避免缺陷而存在的尺寸上的不同。公差范围取决于制造机构的精度、机加工过程和尺寸的量值。
The greater the tolerance range, the cheaper the manufacturing process. A bilateral tolerance is one where the tolerance range is disposed on both sides of the nominal dimension. A unilateral tolerance is one where the tolerance zone is on one side only of the nominal dimension, in which case the nominal dimension may form one of the limits.
公差范围越大，则制造过程的成本就越低。双向公差是在公称尺寸两侧都有公差带的公差。单向公差是仅在公称尺寸一侧有公差带的公差，在这种情况下公称尺寸成了两个极限中的一个。
Limits are the extreme dimensions of the tolerance zone. For example, nominal dimension
30mm tolerance limits
极限是公差带的极限尺寸。例如公称尺寸30毫米公差极限
Fits depend on the relationship between the tolerance zones of two mating parts, and may be broadly classified into a clearance fit with positive allowance, a transition fit where the allowance may be either positive or negative (clearance or interference), an interference fit where the allowance is always negative.
配合取决于两配合零件公差带之间的关系，并且可以概括地分为具有正允差的间隙配合，允差可以是正或负的过渡配合和总是负允差的过盈配合。
?Type of Limits and Fits
极限和配合的类型
The ISO System of Limits and Fits, widely used in a number of leading metric countries, is considerably more complex than the ANSI system.
在一些最主要采用公制的国家中广泛使用的ISO的极限和配合系统，比ANSI的极限和配合系统要复杂得多。
In this system, each part has a basic size. Each limit of size of a part, high and low, is defined by its deviation from the basic size, the magnitude and sign being obtained by subtracting the basic size from the limit in question. The difference between the two limits of size of a part is called the tolerance, an absolute amount without sign.
在这个系统中，每个零件都有基本尺寸。零件尺寸的每一极限，不管大小，都通过对基本尺寸的偏差来定义；其量值和符号由正被讨论的极限减去基本尺寸得到。零件尺寸的两个极限之差称为公差，这是一个没有符号的绝对量值。
There are three classes of fits: 1) clearance fits, 2) transition fits (the assembly may have either clearance or interference), and 3) interference fits.
存在三种配合：1)间隙配合，2)过渡配合(装配后可以有间隙或过盈)，和3)过盈配合。
Either a shaft-basis system or a hole-basis system may be used. For any given basic size, a range of tolerances and deviations may be specified with respect to the line of zero deviation, called the zero line.
基轴制或基孔制均可采用。对任何给定的基本尺寸，公差范围和偏差可以相对于被称为零线的零偏差线来确定。
The tolerance is a function of the basic size and is designated by a number symbol,
called the grade—thus the tolerance grade.
公差是基本尺寸的函数并通过一个被称为等级的数字符号标明—即公差等级。
The position of the tolerance with respect to the zero line also a function of the
basic size—is indicated by a letter symbol (or two letters), a capital letter for
holes and a lowercase letter for shafts. Thus the specification for a hole and shaft having a basic size of 45 mm might be 45H8/g7.
公差相对于零线的位置同样为基本尺寸的函数通过一个或两个字母符号表达，大写字母表示孔而小写字母表示轴。这样基本尺寸为45毫米的一个孔和轴配合规格可能是45H8/g7。
Twenty standard grades of tolerances are provided, called IT01, IT0, IT1~18, providing numerical values for each nominal diameter, in arbitrary steps up to 500mm (for example 0~3, 3~6,6~10, ......, 400~500 mm).
ISO规定了二十种标准的公差等级，称之为IT01，IT0，IT1~18，给在直至500毫米强行分段(例如0~3，3~6，6~10, ......, 400~500毫米)中的公称直径提供具体数值。
The value of the tolerance unit, i, for grades 5~16 isWhere i is in microns and D in millimeters.
对5～16级而言，公差单位i的值可用下式计算这里i的单位是微米，而D的单位是毫米。
Standard shaft and hole deviations similarly are provided by sets of formulas, however, for practical application, both tolerances and deviations are provided in three sets of rather complex tables.
标准的轴和孔偏差同样都由若干公式提供；然而对实际应用，公差和偏差都在三张相当复杂的表格中规定了。
Additional tables give the values for basic sizes above 500 mm and for “Commonly Used Shafts and Holes” in two categories—“General Purpose” and “Fine Mechanisms and Horology”.
对基本尺寸大于500毫米和在“一般用途”和“精密机械和钟表”两个类别中的“常用的轴和孔”而言，由附加的表格给出数值。
Unit 2 Numerical Control of Production Equipment
Unit 2 生产设备的数字控制
Numerical Control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters, and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program of instructions for a particular work-part or job. 数控是程序控制的自动化，在数字控制系统中，设备通过数字，字母和符号
来编码，以一种合适的格式为每一个特定的零件或工件定义一个程序指令集。When the job changes, the program of instructions is changed. The capability to change the program is what makes NC suitable for low-and medium-volume production. It is much easier to write new programs than to make major alterations of the processing equipment.当工件变化时，程序也变
化，改变程序的能力亦适合中小批量生产。写一个新程序比改变大量生产设备要容易的多。
Basic Components of NC
数控基本结构
A numerical control system consists of the following three basic components:
数控系统由下面三部分组成：
? Program of instructions控制程序
? Machine control unit机器控制单元
? Processing equipment加工设备
The general relationship among the three components is illustrated in Fig. 2.1. The program is fed into the control unit, which directs the processing equipment accordingly.
三部分的基本关系，由图2.1 所示。程序输入到控制单元由送入的程序来引导加工设备
控制。
The program of instruction is the detailed step-by-step commands that direct the processing equipment. 指导程序是一步步详细的指导加工设备的指令。In its most common form, the commands refer to positions of a machine tool spindle with respect to the worktable on which the part is fixtured. 通常指令把主轴上刀具相对于安装工具的工作台定位。More advanced instructions include selection of spindle speeds, cutting tools, and other functions. The program is coded on a suitable medium for submission to the machine control unit. 更多先进的
说明包括主轴的转速，加工工具的选择及其功能。The most common medium in use over the last
several decades has been 1-in.-wide punched tape. 程序刻在合适的介质中，提交到机器控制单
元中，在过去几十年中，最常用的介质是一英寸宽的打孔纸带。Because of the widespread use of the punched tape, NC is sometimes called “tape control”. However, this is a misnomer in modern usage of numerical control . 由于打孔纸带的广泛使用，NC 有时也叫纸带控制，然而
这是现代数控使用的误称。Coming into use more recently have been magnetic tape cassettes and
floppy diskettes. 现在进入使用更多的是磁带和软盘。
The machine control unit (MCU) consists of the electronics and control hardware that read and interpret the program of instruction and convert it into mechanical actions of the machine tool or other processing equipment. 机器控制单元（MCU）由电子和控制硬件组成，
机器控制单元可以读出和执行指令程序，可以自动改变加工工具和其他加工设备。
The processing equipment is the third basic component of an NC system. It is the component that performs useful work. 执行单元是数控系统的第三基础部分，执行原件是有效
执行工作的原件In the most common example of numerical control, one that performs
machining operations, 最常见的数控例子其中的一个加工操作，加工设备由工作台和主轴组
成，就像用电动机来驱动一样。the processing equipment consists of the workable and spindle as
well as the motors and controls needed to drive them. 加工设备由控制单元来驱动控制系统的
类型。
Types of Control Systems
控制系统的类型
There are two basic types of control system in numerical control : point-to-point and contouring. In the point-to-point system, also called positioning, each axis of the machine is driven separately by leadscrews and, depending on the type of operation, at different velocities. 数控有
2 种基本类型，点对点式和轮廓式控制，点对点式控制也称定位控制，每个轴都是通过丝杠
单独驱动，根据加工类型不同，加工速度也不一样。The machine moves initially at maximum velocity in order to reduce nonproductive time but decelerates as the tool reaches its numerically defined position. 样。机器开始以最大速度运行来减少非加工时间，但当他达到数据定义的位置时，机器开始减速。Thus in an operation such as drilling or punching, the positioning and cutting take place sequentially. 因此在一个操作中，如钻或冲孔操作先定位在加工。After the hole is drilled or punched, the tool retracts, moves rapidly to another position, and repeats the operation. 在钻或冲孔之后，迅速收起工具移动到另一个位置重复此操作。The path followed from one position to another is important in only one aspect: The time required should be minimized for efficiency. 从一个位置移到另一个位置是非常重要的，要遵循一个原则，从效率上考虑只要时间最短即可。Point-to-point systems are used mainly in drilling, punching, and straight milling operations. 点对点系统主要用于钻，冲孔，直铣操作中。
In the contouring system, also known as the continuous path system, positioning and cutting operations are both along controlled paths but at different velocities. Because the tool cuts as it travels along a prescribed path, accurate control and synchronization of velocities and movements are important. 轮廓式也就是连续路径式系统，定位和切削同时按不同速度来控
制，由于刀具在指定路线运动同时切削，因此速度和运动的同步控制是非常重要的。The
contouring system is used on lathes, milling machines, grinders, welding machinery, and machining centers. 轮廓式系统常用于车床铣床磨床焊接设备和加工中心。
Movement along the path, or interpolation, occurs incrementally, by one of several basic methods. In all interpolations, the path controlled is that of the center of rotation of the tool. Compensation for different tools, different diameter tools, or tool wear during machining, can be made in the NC program. 沿着路径的运动或以增量差补是几个基本方式的一个，在所有的差
补中，要控制刀具的回转中心定位，补偿可以以不同直径及刀具磨损，在数控程序中进行改
写。
There are a number of interpolation schemes that have been developed to deal with the various problems that are encountered in generating a smooth continuous path with a contouring-type NC system. They include: 有一些已形成差补方案来处理数控系统中连续路径
和加工系统产生的问题包括：
? Linear interpolation线性差补
? Ci rcular interpolation圆弧差补
? Helical interpolation螺旋线差补
? Parabolic interpolation抛物线差补
? Cubic interpolation立体差补
Each of these interpolation procedures permits the programmer (or operator) to generate machine instructions for linear or curvilinear paths, using a relatively few input parameters. The interpolation module in the MCU performs the calculations and directs the tool along the path. 每
一种差补程序都允许程序源产生加工指令，适用于相对少的输入参数的直线或曲线路径。储
存在数控单元中的模块预算指引工具沿计算出的路径运动
Linear interpolation is the most basic and is used when a straight-line path is to be generated in continuous-path NC. 线性差补是最基本的差补方法，用于连续路径的数控系统中。Two-axis and three-axis linear interpolation routines are sometimes distinguished in practice, but conceptually they are the same. The programmer is required to specify the beginning point and end point of the straight line, and the feed rate that is to be followed along the straight line. 两轴
和三轴线性差补路线在实际中有时会分辨出的，但在概念上他们是一样的，程序源要明确指
定直线的起点和缺点及沿直线的进给率。The interpolator computes the feed rates for each of
the two (or three) axis in order to achieve the specified feed rate. 差补需计算两轴或三轴的进给
速率以达到设定的进给速度。
Linear interpolation for creating a circular path would be quite inappropriate because the programmer would be required to specify the line segments and their respective end points that are to be used to approximate the circle. 线性差补用来差补圆是不合适的因为程序源需要明确
指定线段部分（线段数量）和各自的终点来大约模拟圆弧。Circular interpolation schemes have been developed that permit the programming of a path consisting of a circular arc by specifying the following parameters of the arc: the coordinates of its end points, the coordinates of its center, its radius, and the direction of the cutter along the arc. 使用圆弧只要给定以下参数，圆弧终点坐
标，圆心坐标，半径和刀具沿圆弧路径的走刀方向。The tool path that is created consists of a series of straight-line segments, but the segments are calculated by the interpolation module rather than the programmer. 向。圆弧
差补也是由许多小的直线段来实现的，但这些小线段的参数由差补模块来计算出来的，
而不是程序员设定的。The cutter is directed to move along each line segment one by one in order
to generate the smooth circular path. 切削是沿着每一小线段一个一个的进行以产生光滑曲线
路径。A limitation of circular interpolation is that the plane in which the circular are exists must
be a plane defined by two axes of the NC system. 圆弧差补的局限性是圆弧路径所在平面是由
数控系统中两轴所决定的平面。
Helical interpolation combines the circular interpolation scheme for two axes described above with linear movement of a third axis. This permits the definition of a helical path in three-dimensional space. 螺旋线差补结合了环形差补两轴在第三轴上做线性运动这样来定义
空间三维螺旋路径。
Parabolic and cubic interpolation routines are used to provide approximations of free-form curves using higher-order equations. 抛物线差补和立方差补法通过高次高程来实现自由曲线。They generally require considerable computational power and are not as common as linear and circular interpolation. 这通常需要有强的计算能力，正因如此，他不如直线差补和环形差补常
见。Their applications are concentrated in the automobile industry for fabricating dies for car body panels styled with free-form designs that cannot accurately and conveniently be approximated by combining linear and circular interpolations. 他们主要用于汽车工业中具有自由风格的车身面，
而这是线性差补和圆弧差补不能精确容易得到的
The most common application of numerical control is for machine tool control. This was the first application of NC and is today the most important commercially. 数控技术运用于数控机床，
这是数控的主要应用。现在主要用于商业。In this section we discuss the machine tool
applications of NC with emphasis on metal machining. 我们仍讨论数控系统特别是金属数控车
床。
Machine Tool Technology for NC
数控车床技术
Each of the five machining processes is carried out on a machine tool designed to perform that process. Turning is performed on a lathe, drilling is done on a drill press, milling on a milling machining, and so on. 每种加工过程都可以在设计的专门车床上来实现加工。在车床上车削，
在钻床上钻，在铣床上加工。There are several different type of grinding operations with a
corresponding variety of machines to perform them. 有几种类型的磨削方法也要有相应种类的
磨床。Numerical control machine tools have been designed for nearly all of the machining
processes. The list includes: 被设计的数控磨床可以进行下列加工包括：
? Drill presses钻加工
? Milling machines, vertical spindle and horizontal spindle铣床立式和卧式主轴
? Turning machi nes, both horizontal axis and vertical axis车床卧式主轴和立式主轴
? Horizontal and vertical boring mills卧式和立式镗床
? Profiling and contouring mills仿形铣床
? Surface grinders and cylindrical grinders平面磨和圆柱磨
In addition to the machining process, NC machine tools have also been developed for
汉译英 Unit1 1.无论你是多么富有经验的演说家，无论你做了多么充足的准备，你都很难在这样嘈杂的招待会上发表演讲。（no matter how） No matter how experienced a speaker you are, and how well you have prepared your speech ，you will have difficulty making a speech at such a noisy reception. 2.就像吉米妹妹的朋友都关系吉米一样，吉米也关系他们（just as） Just as all his sister ’ s friends cared about him, Jimmy cared about them 3.汽车生产商在新车的几处都印有汽车识别号码，以便帮助找回被盗的车辆。（track down）Car manufacturers stamp a vehicle identification number at several places on new cars to help track down stolen vehicles. 4.老师回来时你敢告我状的话，我就不再和你说话了。（tell on） If you dare tell on me when the teacher gets back I won’t say a word to you any more. 5.有些老年人愿意独自过日子，但大多数老人选择和儿女一起生活。（on one’s own） Some elderly people prefer to live on their own while the great majority choose to live with their children. 6.现在需要面对的事情是：如何筹集创建公司所需的资金。（reckon with） Here is something that needs to be reckoned with: how to get the necessary finances to establish the company. Unit2 1.被告是位年仅30岁的女子，她坚持称自己无罪 The defendant, a woman of only 30, kept insisting on her own innocence. 2.总体看来，枣、豆类以及一些多叶的绿色蔬菜是最好的铁质来源。 All tings considered, dates, beans and some leafy green vegetables are the best sources of iron . 3正餐时不供应饮料，饮料会影响消化。 No beverages are served with meals because they interfere with digestion. 4.考虑到那个地区受欢迎的程度，提前订旅馆是明智的。 Taking the popularity of the region into consideration, it is advisable to book hotels in advance. 5.服药后若有呕吐感，请立即停止服用并立刻咨询医生。 If you have a feeling of wanting to throw up after taking this drug, stop taking it immediately and consult your doctors as soon as possible. 6.总结这次讨论时，他说双方都要好好考虑怎样以最有效的方法来解决这一问题。 Summing up the discussion, he said both parties should consider the most effective way to solve the problem. Unit3 1.在思维方面，与他的行为一样，他是非常传统的。 In his thinking, as in his behavior, he is very traditional. 2..教师一旦同意接受新的教学计划，他们就得面对新计划所带给他们的压力。 Once the teachers agree to accept the new teaching program, they have to face the strain it puts on them. 3.从长远看，大学毕业后继续深造而不是直接参加工作是值得的。 In the long run, it is worthwhile to pursue one ’ s study after graduatin g from university instead of going to work directly. 4.由于这所学校的办学宗旨是品德第一，所以道德观和学习成绩受到同样的重视。 As the school operates on the Character First principle, moral values and academic achievements are stressed equally. 5.据说，原定于这个月召开的会议将推迟到下个月召开。
理工学院 毕业设计外文资料翻译 专业：计算机科学与技术 姓名：马艳丽 学号： 12L0752218 外文出处：The Design and Implementation of 3D Electronic Map of Campus Based on WEBGIS 附件： 1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文 基于WebGIS的校园三维电子地图的设计与实现 一．导言 如今，数字化和信息化是当今时代的主题。随着信息革命和计算机科学的发展，计算机技术已经渗透到科学的各个领域，并引起了许多革命性的变化，在这些科目，古代制图学也不例外。随着技术和文化的不断进步，地图变化的形式和内容也随之更新。在计算机图形学中，地理信息系统（GIS）不断应用到Web，制作和演示的传统方式经历了巨大的变化，由于先进的信息技术的发展，地图的应用已经大大延长。在这些情况下，绘图将面临广阔的发展前景。电子地图是随之应运而生的产品之一。随着计算机技术，计算机图形学理论，遥感技术，航空摄影测量技术和其他相关技术的飞速发展。用户需要的三维可视化，动态的交互性和展示自己的各种地理相关的数据处理和分析，如此多的关注应支付的研究三维地图。东北石油大学及其周边地区的基础上本文设计并建立三维电子地图。 二．系统设计 基于WebGIS的校园三维电子地图系统的具有普通地图的一般特性。通过按键盘上的箭头键（上，下，左，右），可以使地图向相应的方向移动。通过拖动鼠标，可以查看感兴趣的任何一个地方。使用鼠标滚轮，可以控制地图的大小，根据用户的需求来查看不同缩放级别的地图。在地图的左下角会显示当前鼠标的坐标。在一个div层，我们描绘了一个新建筑物的热点，这层可以根据不同的地图图层的显示，它也可以自动调整。通过点击热点，它可以显示热点的具体信息。也可以输入到查询的信息，根据自己的需要，并得到一些相关的信息。此外，通过点击鼠标，人们可以选择检查的三维地图和卫星地图。 主要功能包括： ?用户信息管理：检查用户名和密码，根据权限设置级别的认证，允许不同权限的用户通过互联网登录系统。 ?位置信息查询：系统可以为用户提供模糊查询和快速定位。
翻译概论 Warming-up exercises: Translate the followings 1 You are what you think 2 Your abilities count, but the belief that yo u can succeed affects whether or not you will. 3 It’s a pattern of thinking learned at your mother’s knee. I翻译的定义 1.Translation is the replacement of textual material in one language by equivalent textual material in another language. 即“将一种语言的篇章材料替换为与之对等的另一种语言的篇章材料”。翻译是运用一种语言把用另一种语言文字所表达的思想内容准确而完整地重新表达出来的语言活动。它是一门科学，具有描述性；同时它也是一门艺术，因为它具有创造性。
II翻译原则或标准：严复理论 1 信(truthfulness/faithfulness)：忠实原文（对原文的思想不歪曲也不要任意增减；对原文的风格不随意改动，即粗糙的不译成高雅，口语体不译成书面体） 2 达(expressiveness)：语言通顺畅达（译文应该按照译语的语法和习惯来遣词造句；译文避免生搬硬套，应该通顺流畅） Eg . John can be relied on. He eats no fish and plays the game. 约翰值得信赖。他忠诚而正直(守规矩)。 3 雅(elegance)：文字古雅/ 切（closeness） 总之，做英译汉时，按中国人的说话思维方式，把内容用通俗的汉语顺畅地表达出来；反之亦然。 1. It therefore becomes more and more important that, if students are not to waste their opportunities, there will have to have much more detailed information about courses and more advice.
Unit1 1、What is the difference between an alloy and a pure metal? Pure metals are elements which come from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and aluminum in cooking foil and beverage cans. 合金与纯金属的区别是什么？纯金属是在元素周期表中占据特定位置的元素。例如电线中的铜和制造烹饪箔及饮料罐的铝。 Alloys contain more than one metallic element. Their properties can be changed by changing the elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of iron, nickel, and chromium; and gold jewelry which usually contains an alloy of gold and nickel. 合金包含不止一种金属元素。合金的性质能通过改变其中存在的元素而改变。金属合金的例子有：不锈钢是一种铁、镍、铬的合金，以及金饰品通常含有金镍合金。 2、 Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio. 为什么要使用金属和合金？许多金属和合金具有高密度，因此被用在需要较高质量体积比的场合。 Some metal alloys,such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable. 某些金属合金，例如铝基合金，其密度低，可用于航空航天以节约燃料。许多合金还具有高断裂韧性，这意味着它们能经得起冲击并且是耐用的。 3、The atomic bonding of metals also affects their properties. In m etals, the outer valence electrons are shared among all atoms, and ar e free to travel everywhere. Since electrons conduct heat and electri city, metals make good cooking pans and electrical wires. 金属的原子连结对它们的特性也有影响。在金属内部，原子的外层阶电子由所有原子共享并能到处自由移动。由于电子能导热和导电，所以用金属可以制造好的烹饪锅和电线。 It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through. 因为这些阶电子吸收到达金属的光子，所以透过金属不可能看得见。没有光子能通过金属. 4、Some of the useful properties of ceramics and glasses include high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance. 陶瓷和玻璃的特性高熔点、低密度、高强度、高刚度、高硬度、高耐磨性和
新视野大学第三版book1英语课后翻译答案 Unit1 苏格拉底是古希腊哲学家，被誉为现代西方哲学的奠基人。他是一个谜一般的人物，人们主要通过后来的一些古典作家的叙述，尤其是他最著名的学生柏拉图的作品去了解他。苏格拉底以他对伦理学的贡献而闻名。他的教学法亦称为苏格拉底法，即通过提问和回答来激发批判性思维以及阐述观点。该方法在各种讨论中仍被普遍使用。他还在认识论和逻辑领域作出了重大而深远的贡献。他的思想和方法所带来的影响一直是后来的西方哲学的坚实基础。苏格拉底是古代哲学史上最丰富多彩的人物。他在他那个时代已威名远扬。虽然他未曾建立什么哲学体系，未曾设立什么学派，也未曾创立什么宗派，但他的名字很快就变得家喻户晓了。 Confucius was a great thinker and educator in Chinese history. He was the founder of Confucianism and was respectfully referred to as an ancient “sage”. His words and life story were recorded in The Analects. An enduring classic of ancient Chinese culture, The Analectshas had a great influence on the thinkers, writers, and statesmen that came after Confucius. Without studying this book, one could hardly truly understand the thousands-of-years’traditional Chinese culture. Much of Confucius’thought, especially his thought on education, has had a profound influence on Chinese society. In the 21st century, Confucian thought not only retains the attention of the Chinese, but it also wins an increasing attention from the international community. Unit2 圣诞节是一个被广泛庆祝的文化节日，全世界有许许多多的人在12月25日庆祝这一节日。它是为了纪念耶稣基督的诞辰。该节日最早可追溯到公元336年。渐渐地，这一节日演变为一个既是宗教又是非宗教的节日，越来越多的非基督徒也庆祝圣诞节。如今，圣诞节在全球被作为一个重大的节日和公共假日来庆祝。不同国家的圣诞节风俗也各不相同。现代流行的圣诞接风俗包括交换圣诞贺卡和圣诞礼物、唱圣诞歌曲、参加教堂活动、摆放各种圣诞装饰品和圣诞树、举行家庭聚会以及准备一顿特别的大餐。对小孩子们来说，这个节日充满了幻想和惊喜。据传说，圣诞老人会在圣诞夜从烟囱进入每户人家，给乖巧听话的孩子带来礼物。由于圣诞节送礼物以及许多其他方面推动了基督徒和非基督徒的经济活动，圣诞节也因此成为商家的一个重大活动和主要销售季。 According to the Chinese lunar calendar, August 15 of every year is a traditional Chinese festival-the Mid-Autumn Festival. This day is the middle of autumn, so it is called Mid-Autumn. One of the important Mid-Autumn Festival activities is to enjoy the moon. On that night, people gather together to celebrate the Mid-Autumn Festival, looking up at the bright moon and eating moon cakes. The festival is also a time for family reunion. People living far away from home will express their feelings of missing their hometowns and families at this festival, all expressing people’s love and hope for a happy life. Since 2008, the Mid-Autumn Festival has become an official national holiday in China.
考研翻译重点词汇 Abstract n.摘要，概要，抽象 adj.抽象的，深奥的，理论的 Accelerate vt.&vi.（使）加快，（使）增速， n.接受速成教育的学生 Account (1)看法,认识 (2)解释,说明 Account for 占…(多大)比重; 解释, 说明 Achievement n.成就；成绩；功绩，达到；完成 Acquire vt.得到，养成，vt 获得；招致，学得（知识等），求得，养成（习惯等），捕获， Action n.作用，动[操]作，行动，机械装置[作用]，（小说等中的）情节 Activity n.活动，活动的事物，活动性，机能，功能 Actually adv.现实的，实际的；目前的；明确的，有效的 Additional adj.增加的，额外的，另外的 Advance vt.&vi.（使）前进，（使）发展；促进， vt.提出 Advantage n.利益，便利，有利方面，有利条件；优点；优势， （网球等）打成平手（deuce ）而延长比赛后一方先得的一分（攻方所得称 advantage in ，守方所得则称 advantage out ） Agree vi.一致；相合同意，赞成约定，允诺，答应，相宜，调和，符合，和睦相处 Almost adv.几乎，差不多，差一点；将近 Amount n.量，数量，数额，总额，总数 vi.合计，共计 An immense amount of … 大量 An amount of … 一些 A certain amount of … 某些 Analogous 与…类似, 与…相似 And 而, 然而 Apply … to … ≈ lie with 存在于,发生于 Approach vt.&vi.接近，走近，靠近； vt.接洽，交涉；着手处理； n.靠近，接近，临近 Appropriate adj.适当的，恰当的； vt.挪用；占用；盗用 Argue vt.&vi.争吵，辩论； vt.坚决主张，提出理由证明，说服，劝说 Arise vi.&link v.呈现；出现；发生； vi.起身，起来，起立 As 译为 (1) 像, 如 ; (2) 作为 As … as (比较的两者要一致) = not so … as 译成:“… 和 … 一样 ” As is mentioned above 如上所述, (如上所示,如图所示---作文可以写) Aspect n.方面，方位，朝向 Assert vt.声称，断言，维护，坚持 Assume vt.假设，认定, 臆断，猜想，假装，担，担任，就职 Attempt n.尝试，企图vt.尝试，企图 Augment vt.增加，提高，扩大； n.增加，提高，扩大 Availability n.可用性，有效性，实用性 Base n.基础，底座，基地，根据地 vt.把…建立在，以…为基础 Behavioral adj.动作的，行为方面的 Big bang 大爆炸理论 Branch n.树枝，枝条，支，分科，分系； vi.出枝，树叉 Breakthrough : 突破 Break prison (监狱)越狱 Break out v. 爆发 Out break: n. 爆发
1.我们可以把钢再次加热到临界温度以下的某一温度，然后在慢慢让其冷却。We can heat the steel again to a temperature below the critical temperature, then cool it slowly. 2.无论任何简单的机床，都是由单一元件即通称为机械零件或部件组成的。However simple, any machine is a combination of individual components generally referred to as machine elements or parts. 3.这些金属不都是好的导体。 All these metals are not good conductors. 4. 在做带电实验的时候，再怎么小心都不为过。 You can't be too careful in performing an experiment. 5.利用发电机可以把机械能转变成电能。 The mechanical energy can be changed back into electrical energy by means of a generator or dynamo. 6.假定电源输入的电压保持不变。 Assume that the voltage input of the power supply remains the same. 7.化石燃料是发电过程中最为频繁使用的能源。 Fossil fuels are most frequently used source daring the power generation process. 8单个机械零件的可靠性成为评估整台机器使用寿命的基本因素。 The individual reliability of machine elements becomes the basis for estimating the overall life 9.说我们生活在一个电子时代，这一点都不夸张。 It's no exaggeration to say that we live in an electronic age. 10.发动机的转速不应超过最大允许值。 Engine revolution should not exceed the maximum permissible. 11.如能从大型核电站获得成本极低的电力，电解氢的竞争能力就会增强。（Electrolytic hydrogen）。 If extremely low-cost power were ever to become available from large nuclear power plants, electrolytic hydrogen would become competitive. 12.电子技术提供了一种新的显示时间的方法。 A new way of displaying time has been given by electronics. 13.远距离输电需要高压，安全用电需要低压。 High voltage is necessary for long transmission line while low voltage for safe use. 14.铝的电阻大约是同等尺寸的铜的1.5倍。 The resistance of aluminum is approximately half again as great as that of copper for the same dimensions = size 15.In fact,it is impossible for no force to be exerted on a body,since in this world everything is subject to the for ce of gravity. 事实上，物体不受外力作用是不可能的，因为在这个世界上任何物体都要受到重力的作用。 16.In a thermal power plant,all the chemical energy is not
Unit1 1. 背离传统需要极大的勇气。(departure, enormous) {It takes an enormous amount of courage to make a departure from the tradition.} 2. 汤姆过去很腼腆，但这次却非常勇敢能在大庭广众面前上台表演了。(performance, bold) {Tom used to be very shy, but this time he was bold enough to give a performance in front of a large audience.} 3. 很多教育家认为从小培养孩子的创新精神是很可取的。 (creative, desirable) {Many educators think it desirable to foster the creative spirit in the child at an early age.} 4. 假设（assume）那幅画确实是名作（masterpiece），你觉得值得购买吗？(worthwhile) {Assuming (that) this painting really is a masterpiece, do you think it's worthwhile to buy / purchase it?} 5. 如果这些数据统计上是站得住脚的，那它将会帮助我们认识正在调查的问题。(throw light on , investigate, valid) {If the data is statistically valid, it will throw light on the problem we are investigating.} Unit2 1) 该公司否认其捐款有商业目的。(deny, commercial) {The company denied that its donations had a commercial purpose.} 2) 每当他生气的时候，他说话就有一点结巴。(stammer) {Whenever he was angry, he would begin to stammer slightly.} 3) 教育是我们家庭最看重的传统，这就是为什么我父母从不带我到昂贵的饭店吃饭，却送我到最好的私立学校上学。(cherish) {Education is the most cherished tradition in our family. That’s why my parents never took me to dinner at expensive restaurants, but sent me to the best private school.} 4) 手术康复后不久，他失业了，因此经历了人生的又一个困难阶段。(shortly after, go through) {Shortly after he recovered from the surgery, he lost his job and thus had to go through another difficult phase of his life.} 5) 与我们的富裕邻居相比，我们的父母就相当穷了，但是他们总是努力满足我们最起码的需求。(affluent, minimal) {In contrast to our affluent neighbors, my parents are rather poor, but they have always tried hard to meet our minimal needs.} Unit3 1) 科学家们找到火星上有水的证据了吗？(proof) {Have scientists found proof of water on Mars?} 2) 计划委员会已经将建核电厂的可能地点缩小到了两个沿海城镇。(location, narrow down) {The planning committee has narrowed down the possible locations for the nuclear power plant to two coastal towns.} 3) 任何一个有尊严的人都不会一辈子依靠社会救济过活。(welfare)
72页 Machine Tools Objectived. Machine tools are the main engines of the manufacturing industry. This chapter covers a few of the details that are common to all classes of machine tools discussed in this book. After completing the chapter, the reader will be able to >understand the classification of the various machine tools used in manufacturing industries. >identify the differences between generating and forming of surfaces. > identify various methods used to generate different types of surfaces. >distinguish between the different accuracies and surface finishes that are achievable with different machine tools. >understand the different components of the machine tools and their functions. >learn about the different support structures used in the machine tools. >understand the various actuation systems that are useful to generate the required surfaces. >Learn the different types of guideways used in the machine tools. >understand the work holding requirements. 3.1 INTRODUCTION The earliest known machine tools are the Egyptian foot-operated lathes.
第1 课绪论--翻译概述（1） 一、学科特点 翻译是一种跨越时空的语言活动，是"把一种语言已经表达出来的东西用另 一种语言准确而完整地重新表达出来"(范存忠："漫谈翻译"《翻译理论与技巧》 中国对外翻译出版公司，1985，p.80), 是"从语义到文体在译入语中用最切近而 又最自然的对等语再现原语的信息"（谭载喜：《奈达论翻译》中国对外翻译出版 公司，1984，p.10）。翻译虽为个体所承作，却是一种社会活动，一门综合性很 强的学科。它既有很强的理论性又有丰富的实践内涵。就前者而言，翻译经过千 百年来各国翻译家的共同努力，已经在语言学、文学、文化、心理学、人类学、 哲学和教育学等学科的基础上初步建立了一套理论体系，并在具体实践中总结出 了一套行之有效的跨文化和语言转换模式。随着科学的日益进步，这种体系和模 式正处在不断地完善之中。就后者而言，翻译是人类社会活动的产物，具有很强
的实践性。翻译理论与实践的关系是辨证的；翻译理论产生于翻译实践，反过来 又指导实践，实践转过来又丰富翻译理论。可以说，没有社会实践就不会有翻译 理论的产生；没有翻译理论作为指导，翻译实践就会难免走弯路。因此，学好翻 译既要重视翻译理论的学习，又要加强翻译实践；理论联系实际，这是我们学好 翻译的必由之路。 二、为什么可能有翻译 翻译是人类社会发展和进步的需要，因为人类社会要发展进步就需要在不同 文化的民族之间进行沟通，而这一全过程都离不开翻译。正如Steiner 和张培基 所说的那样：Translating it is that openeth the window, to let in the light; that breaketh the shell, that we may eat the kernel. (Steiner) 翻译是沟通各族人民的思 想，促进政治、经济、文化、科学、技术交流的重要手段，也是进行国际斗争的 必要武器。翻译是学习好外语的重要手段之一，也是探讨两种语言对应关系的一 门学科。(张培基等)
2、应力和应变 在任何工程结构中独立的部件或构件将承受来自于部件的使用状况或工作的外部环境的外力作用。如果组件就处于平衡状态,由此而来的各种外力将会为零,但尽管如此,它们共同作用部件的载荷易于使部件变形同时在材料里面产生相应的内力。 有很多不同负载可以应用于构件的方式。负荷根据相应时间的不同可分为: (a)静态负荷是一种在相对较短的时间内逐步达到平衡的应用载荷。 (b)持续负载是一种在很长一段时间为一个常数的载荷, 例如结构的重量。这种类型的载荷以相同的方式作为一个静态负荷; 然而,对一些材料与温度和压力的条件下,短时间的载荷和长时间的载荷抵抗失效的能力可能是不同的。 (c)冲击载荷是一种快速载荷(一种能量载荷)。振动通常导致一个冲击载荷, 一般平衡是不能建立的直到通过自然的阻尼力的作用使振动停止的时候。 (d)重复载荷是一种被应用和去除千万次的载荷。 (e)疲劳载荷或交变载荷是一种大小和设计随时间不断变化的载荷。 上面已经提到，作用于物体的外力与在材料里面产生的相应内力平衡。因此,如果一个杆受到一个均匀的拉伸和压缩，也就是说, 一个力,均匀分布于一截面,那么产生的内力也均匀分布并且可以说杆是受到一个均匀的正常应力,应力被定义为 应力==负载 P /压力 A, 因此根据载荷的性质应力是可以压缩或拉伸的,并被度量为牛顿每平方米或它的倍数。 如果一个杆受到轴向载荷，即是应力，那么杆的长度会改变。如果杆的初始长度L和改变量△L已知，产生的应力定义如下: 应力==改变长△L /初始长 L 因此应力是一个测量材料变形和无量纲的物理量 ,即它没有单位;它只是两个相同单位的物理量的比值。 一般来说,在实践中,在荷载作用下材料的延伸是非常小的, 测量的应力以*10-6的形式是方便的, 即微应变, 使用的符号也相应成为ue。 从某种意义上说，拉伸应力与应变被认为是正的。压缩应力与应变被认为是负的。因此负应力使长度减小。 当负载移除时，如果材料回复到初始的，无负载时的尺寸时，我们就说它是具有弹性的。一特定形式的适用于大范围的工程材料至少工程材料受载荷的大部分的弹性, 产生正比于负载的变形。由于载荷正比于载荷所产生的压力并且变形正比于应变, 这也说明,当材料是弹性的时候, 应力与应变成正比。因此胡克定律陈述, 应力正比于应变。 这定律服从于大部分铁合金在特定的范围内, 甚至以其合理的准确性可以假定适用于其他工程材料比如混凝土，木材，非铁合金。 当一个材料是弹性的时候，当载荷消除之后，任何负载所产生的变形可以完全恢复,没有永久的变形。
大学英语（B）1翻译练习参考译文 1、元宵节是春节后的第一个重要节日。元宵节的习俗在全国各地不尽相同，其 中赏花灯（lanterns exhibits）、猜灯谜、吃元宵等是几项最常见的民间习俗。据说， 吃元宵的习俗起源于汉代，唐宋时期开始盛行。如今，元宵已成为人们的日常饮 食之一，在超市一年四季都可以买到。 The Yuanxiao Festival is the first important festival after the Spring Festival. Although customs of the festival vary from region to region, the most common ones include appreciating lantern exhibits, trying to solve riddles written on lanterns, and eating yuanxiao. It is said that the custom of eating yuanxiao originated from the Han Dynasty and became popular during the Tang and Song periods. Nowadays, yuanxiao has become a food in people’s daily life, which is available in supermarkets a ll the year round. 8、如今，越来越多的大学生抱怨很难找到好的工作。造成这一现象的原因如下： 首先，大学生把在校的大多数时间都用在了专业学科的学习上，只有当他们开始 找工作的时候，才意识到自己缺乏必要的专业培训。其次，大学生之间的竞争也 越来越激烈，这导致任何一名大学生找到工作的机会都变小了。 Nowadays, more and more university students complain about having great difficulties in finding a good job. The reasons f or this phenomenon are as follows: First, college students spend most of their time at school studying academic subjects and it is only when they start looking for a job that they realize they lack necessary job training. Second, competition among graduates has become more and more fierce. And this results in a decreased chance for any individual graduate to find a job. 7、杭州是中国著名的六大古都之一，已有两千多年的历史。这个城市不仅以自 然美闻名于世，而且有着传统的文化魅力。不仅有历代文人墨客（men of letters） 的题咏，而且有美味佳肴和漂亮的工艺品。一般来说，游览杭州西湖及其周边景 点花上两天较为合适。到杭州旅游，既令人愉快，又能得到文化享受。 Hangzhou, one of China’s six ancient capital cities, has a history of more than 2,000 years. It is famous not only for its natural beauty but also for its charm of cultural traditions. Besides many poems and inscriptions by men of letters through the dynasties, it also boasts local delicacies and pretty handicrafts. Generally speaking, a two-day tour of West Lake and scenic spots around it is advisable for a tourist. As a tourist, you will find it a pleasant and culturally rewarding trip to Hangzhou. 6、说到中国古代的科技文明（civilization），人们自然就会想到“四大发明”，即 指南针、火药、造纸术和印刷术。这四种发明是古代先进科技的象征，具有重大 的历史意义。它们对中国古代政治、经济、文化的发展产生了巨大的推动作用， 也对世界的文明进程产生了巨大影响。 Speaking of ancient Chinese civilization in science and technology, people will naturally think of the Four Great Inventions, namely the compass, gunpowder, paper-making and printing. These four inventions are symbols of ancient China’s