about all of the function aspects of the product. 译文：设计工程师最好能在这一阶段全部完成材料的分析、选择和确定工作，而不是将其留到生产设计阶段，因为在生产设计阶段材料的更换是由其他人员进行的，这些人对产品的所有功能的了解可能不如设计工程师。 幻灯片12
Ordinary English and Scientific English
? We made a hole in a cork and pushed it into a narrow glass tube. Then we pushed this into the neck of a bottle which we had filled with colored water. When we did this, some of the colored water went up into the tube. We marked the level of the colored water in the tube. Then we put the bottle into a pan of hot water.
? After a hole was made in a cork, a narrow glass tube was inserted and the cork was inserted into the neck of a bottle filled with colored water. On doing this, some of the colored water rose the tube. The level of the colored water in the tube was marked. Then the bottle was placed into a pan of hot water.
幻灯片13
Ordinary English 通俗化：常用词汇用得多 Scientific English 专业化：专业术语用得多 多义性：一词多义，使用范围广 单义性：词义相对单一，因专业而不同 人称化：人称丰富，形式多样 多时性：描述生活，时态多样 主动性：句子倾向于用主动态 简单性：单句、散句用的多 物称化：多用物称，以示客观 现时性：叙述事实多用现在时 被动性：句子倾向于用被动 复杂性：复杂单句用得多，复合句用得多 口语化：口语用得多，随意灵活 书面化：长句用得多，书卷气浓
5.1 Introduction
Conventional machining is the group of machining operations that use single- or multi-point tools to remove material in the form of chips. Metal cutting involves removing metal through machining operations. Machining traditionally takes place on lathes, drill presses, and milling machines with the use of various cutting tools. Most machining has very low set-up cost compared with forming, molding,
and casting processes. However, machining is much more expensive for high volumes. Machining is necessary where tight tolerances on dimensions and finishes are required. 幻灯片5 5.1 译文
传统机械加工是一组利用单刃或者多刃刀具以切屑形式去除材料的加工方式。金属切削意味着通过机械加工去除金属。传统的机械加工都是利用不同的刀具在车床、钻床和铣床上进行的。与成型加工、锻压和铸造工艺相比，大多数机械加工的生产准备成本都较低，然而如果是大批量生产，其成本要高得多。当对零件的尺寸公差和光洁度要求较高时，机械加工是很有必要的。 幻灯片6
5.2 Turning and Lathe
Turning is one of the most common of metal cutting operations. In turning, a workpiece is rotated about its axis as single-point cutting tools are fed into it, shearing away excess material and creating the desired cylindrical surface. Turning can occur on both external and internal surfaces to produce an axially-symmetrical contoured part. Parts ranging from pocket watch components to large diameter marine propeller shafts can be turned on a lathe.
Apart from turning, several other operations can also be
performed on lathe. 幻灯片7 marine propeller 幻灯片8
Words & expressions axially ['?ksi?li] adv.轴向地 symmetrical [si'metrik?l] a. 对称的 cylindrical [si'lindrikl] a.圆柱形的
contoured ['k?ntu?d] a.显示轮廓的，与某种形体轮廓相吻合的 译文:
在金属切削加工操作中，车削是最常见的一种。在车削过程中，工件绕其轴线回转，单刃车刀沿工件进给，切除掉多余的材料，最后形成要求的圆柱形表面。车削可以加工外面和内表面以形成具有轴对称的成形工件。从怀表的零件到大直径的船用螺旋桨轴都可以在车床上加工。
除了车削，还有另外几种加工操作都可以在车床上进行。 幻灯片9
5.2 Turning and Lathe
Boring and internal turning. Boring and internal turning are performed on the internal surfaces by a boring bar or suitable internal cutting tools. If the initial workpiece is solid, a drilling operation must be performed first. The drilling tool is held in the tailstock, and the
latter is then fed against the workpiece. When boring is done in a lathe, the work usually is held in a chuck or on a face plate. Holes may be bored straight, tapered, or to irregular contours. Boring is essentially internal turning while feeding the tool parallel to the rotation axis of the workpiece. 幻灯片10
5.2 Turning and Lathe
Words & expressions
tailstock ['teilst?k] n. 尾座 chuck [t??k] n.卡盘，夹头 译文:
利用镗杆或合适的内圆车刀可以进行镗削和车内圆。如果工件毛坯是实心的，首先要钻孔。钻头安装在尾架上，后者向工件进给。如果在车床上进行镗削加工，工件通常装夹在卡盘或者花盘上。镗出的孔可以是直孔、锥孔或者不规则轮廓。当将刀具沿工件的回转轴线平行进给时，镗削实际上就是车内圆。 幻灯片11 face plate chuck 幻灯片12
5.2 Turning and Lathe