车床手柄座（831015）加工工艺及关键工序工装设计【钻φ14孔】【说明书+CAD】

车床手柄座（831015）加工工艺及关键工序工装设计【钻φ14孔】【说明书+CAD】,钻φ14孔,说明书+CAD,车床手柄座（831015）加工工艺及关键工序工装设计【钻φ14孔】【说明书+CAD】,车床,手柄,831015,加工,工艺,关键,工序,工装,设计,14,说明书,CAD 南京理工大学泰州科技学院 毕业设计(论文)开题报告 学 生 姓 名： 陈游 学 号： 05010113 专 业： 机械工程及自动化 设计(论文)题目： 车床手柄座加工工艺及关键工序 工装设计 指 导 教 师: 王栓虎 年 月 日 开题报告填写要求 1．开题报告（含“文献综述”）作为毕业设计（论文）答辩委员会对学生答辩资格审查的依据材料之一。此报告应在指导教师指导下，由学生在毕业设计（论文）工作前期内完成，经指导教师签署意见及所在专业审查后生效； 2．开题报告内容必须用黑墨水笔工整书写或按教务处统一设计的电子文档标准格式（可从教务处网页上下载）打印，禁止打印在其它纸上后剪贴，完成后应及时交给指导教师签署意见； 3．“文献综述”应按论文的格式成文，并直接书写（或打印）在本开题报告第一栏目内，学生写文献综述的参考文献应不少于15篇科技论文的信息量，一般一本参考书最多相当于三篇科技论文的信息量（不包括辞典、手册）； 4．有关年月日等日期的填写，应当按照国标GB/T 7408—94《数据元和交换格式、信息交换、日期和时间表示法》规定的要求，一律用阿拉伯数字书写。如“2009年3月15日”或“2009-03-15”。  毕 业 设 计（论 文）开 题 报 告 1．结合毕业设计（论文）课题情况，根据所查阅的文献资料，每人撰写 2000字左右的文献综述： 文 献 综 述 摘要: 本文介绍的是机械加工的现状和发展趋势,以及加工工艺的应用和特点, 夹具在加工过程中的应用。 关键词 工序 工艺 夹具 我所做的是CA6140车床手柄座加工工艺及关键工序工装设计,工艺规程在加工中起了重要作用，夹具的设计也对加工零件的加工过程起了重要意义。 1 国内机械制造业的现状 曾有人在网上发起“中国的机械业落后欧美国家多少年”的讨论，很多人认为“至少30年的差距是有的”。 当前，中国机械制造业正处于历史上难得的发展机遇期，机械制造业持续六年高速发展。固定资产投资和出口的快速增长是中国机械工业高速增长的两大动力。现在，很多因素的出现都在预示着中国整个机械制造业的发展要出现一个拐点。 现在，中国机械制造业正处于历史上难得的发展机遇期，机械制造业持续六年高速发展。固定资产投资和出口的快速增长是中国机械工业高速增长的两大动力。现在，很多因素的出现都在预示着中国整个机械制造业的发展要出现一个拐点。 2 机械制造业的发展前景 制造技术是制造业发展的主体技术 制造技术是制造业为国民经济建设和人民生活生产各种必需物质所使用的一切技术的总称，是将原材料和其他生产要素集聚合理地转化为可直接使用的成品和技术服务的技术群。传统的机械制造技术不断吸收计算机、信息、自动化、新材料、新能源和现代系统管理技术和最新成果，将其综合运用于产品的研究与开发、设计、生产、管理和市场开拓、取得显著的社会经济效益，从而形成了现代的先进制造技术。不同科学之间的交叉融合将产生新的科学聚集，经济的发展和社会的进步对科学技术产生新的要求和期望，这种聚集和期望称为科学前沿。科学前沿可理解为已解决和为解决的科学问题之间的界域。科学前沿具有明显的时域、领域和动态特性。随着科技的发展，昨天的科学前沿今天可能已成为过去，而原来认为不能解决的科学问题现在已成为可能。 加工工艺的选择及应用 众所周知，产品精度或是工装夹具精度的高低在很大程度上取决于加工工艺的科学合理性，正确合理的工艺在产品及工装夹具制造过程中起着举足轻重的作用，所以要制造高精度的产品或工装夹具必须采用正确合理的工艺来保证。 3 机械加工工艺规程概述 机械加工工艺规程是规定零件制造工艺过程和操作方法等的工艺方法。它是根据加工对象的具体情况和实际的生产条件，采用合理的加工方法和过程，按规定的形式制订的。 工艺规程是指生产的主要技术文件。在制订工艺规程时，首先要确保科学性与合理性，并在生产实践中不断改进和完善，而在生产中，则必须严格地执行既定的工艺规程，这是产品质量、生产效率和经济效益的保证。 工艺规程是生产组织和管理工作的基本依据。由工艺规程所涉及的内容可见，产品投产前原材料及毛坯的供应，通用工艺装备的准备。机床负荷的调整，专用工艺装备的设计和制造，作业计划的编排，劳动力的组织以及生产成本的核算等，都是以工艺规程作为基本依据的。 在新建或扩建工厂或车间时，只有根据生产纲领和工艺规程才能正确地确定生产所需的机床和其他设备的种类、规格和数量，车间的面积，机床的布置，生产工人的工种、等级和数量以及辅助部门的安排等。因此，工艺规程也是工厂基础建设的基本资料。 4 机床夹具设计的作用及要求 夹具是卡紧工件用的。比如机床加工时，主轴有几千转的转速，工件必须要固定好，否则工件飞出伤人后果严重。卡具设计要合理，即卡紧可靠，又要定位准确，较少误差，并保护好已加工好的表面。才能保证工件质量。夹具是机械加工不可缺少的部件,在机床技术向高速、高效、精密、复合、智能、环保方向发展的带动下，夹具技术正朝着高精、高效、模块、组合、通用、经济方向发展。为保证工件的加工要求，必须使工件在机床上处于准确的位置，夹具就是用来实现这一要求的。 4.1夹具的作用 为了保证加工精度应采用夹具安装，可以准确地确定工件与机床、刀具之间的相互位置，工件的位置精度由夹具保证，不受工人技术水平的影响，其加工精度高而且稳定。 提高生产率、降低成本 用夹具装夹工件，无需找正便能使工件迅速地定位和夹紧，显著地减少了辅助工时。 4.2夹具的要求 (1) 保证工件加工的各项技术要求 要求正确确定定位方案、夹紧方案，正确确定刀具的导向方式，合理制定夹具的技术要求，必要时要进行误差分析与计算。 (2) 具有较高的生产效率和较低的制造成本 为提高生产效率，应尽量采用多件夹紧、联动夹紧等高效夹具，但结构应尽量简单,造价要低廉。 (3) 尽量选用标准化零部件 尽量选用标准夹具元件和标准件，这样可以缩短夹具的设计制造周期，提高夹具设计质量和降低夹具制造成本。 (4) 夹具操作方便安全、省力 为便于操作，操作手柄一般应放在右边或前面；为便于夹紧工件，操纵夹紧件的手柄或扳手在操作范围内应有足够的活动空间；为减轻工人劳动强度，在条件允许的情况下，应尽量采用气动、液压等机械化夹紧装置。 (5) 夹具应具有良好的结构工艺性 所设计的夹具应便于制造、检验、装配、调整和维修。 5 总结 通过上网查阅相关资料，对车床手柄座加工工艺的编制和车夹具设计的理解，让我明白了机械制造加工工艺的编制对机械产品的制造是相当重要的，直接影响着机械产品的加工质量和生产效益。 参 考 文 献 [1]吴恒文.机械制造概论[M].重庆:重庆大学出版社,1993 [2]赵月望.机械制造技术实践[M].北京:机械工业出版社,1993 [3]巩秀长.机床夹具设计原理[M].济南:山东大学出版社,1993 [4]谢纪坊.机械制造概论[M].重庆:航空工业出版社,1990 [5]张万昌.机械制造实习[M].北京:高等教育出版社,1991 [6]张力真.金属工艺学实习教材[M].北京:高等教育出版社,1991 [7]李庆余 张佳.机械制造装备设计[M].机械工业出版社,2003 [8]吴国华.金属切削机床[M].北京:机械工业出版社,1999 [9]顾维邦.金属切削机床概论[M].北京:机械工业出版社,1991 [10] 赵汝嘉. 计算机辅助工艺设计[M].北京：机械工业出版社，1995 [11] 王小慧. 尺寸设计理论及应用[M].北京；国防工业出版社，2004 [12]冯辛安.机械制造装备设计[M].北京:机械工业出版社,2002 [13]陆剑中,孙家宁.金属切削原理与刀具[M].北京:机械工业出版社,1998 [14]宋殷.机床夹具设计[M].开封:河南科学技术出版社,1985 [15]王先奎.机械制造工艺学[M].北京:机械工业出版社,1995  毕 业 设 计（论 文）开 题 报 告 ２．本课题要研究或解决的问题和拟采用的研究手段（途径）： 通过对机床的夹具设计，可以有效的培养我们的综合应用机械制造知识，并根据工程实际要求，进行问题的分析解决，从而提高独立工作的能力。 1 要研究的问题 1）了解CA6140机床的特点 根据通用机床的特点，了解普通机床的传动方式以及普通组合机床所要求的技术参数，进而分析CA6140机床的结构特点。 2）根据生产专用零件进行零件结构工艺性分析 根据零件制造的工艺路线，进行零件结构工艺性分析，找出合适的定位基准。 3）了解机床的夹具特点 查阅书籍资料，分析普通机床夹具的结构特点，针对生产的专用零件的表面特点和技术要求，设计合适的加工机床夹具结构。 4）选材 设计中对材料的选择应该考虑成本，并且能保证零件设计的准确性，同时还要对零件在各种情况下的切削力范围、承载能力等进行计算，最终达到所设计的零件的使用要求。 2 研究的手段 1）查找相关的资料和书籍，为设计寻找依据。 通过书籍和网络查找最新的夹具设计的发展动向，尽量在保证原来参数的基础上，采用最新的一些结构，这样才能使设计具有实用性和创新性。 2）了解一般代表性机床夹具的设计 了解铣床的夹具设计和镗床的夹具设计，镗铣组合机床的夹具是镗床和铣床的夹具集合体，所以清楚镗床和铣床的夹具设计对加工机床手柄座的夹具设计是很重要的。 3）合理的设计夹具的结构使之满足经济性，生产率，加工质量的要求。 机械制造中一个很重要的指标就是生产成本的经济性，在很大程度上决定了该产品的研制和销售以及运用情况，因此在设计机构时要考虑该机构的科学性、规范性、结构的通用性、部件的标准性和零件的可换性，这样设计出来的机构才具有实用性和可推广性。 4）用相关的绘图软件画出零件图和装配图。 用AutoCAD绘出零件图和装配图。同时对照课题任务的内容和要求，对具体参数进行设计和计算，选择合适的结构和部件，手工画出重要部件或者结构的视图，同时通过指导老师的指导对每一个可执行的方案进行最后的分析和确认，最后写设计说明书。  毕 业 设 计（论 文）开 题 报 告 指导教师意见： 1．对“文献综述”的评语： 2．对本课题的深度、广度及工作量的意见和对设计（论文）结果的预测： 指导教师： 年 月 日 所在专业审查意见： 负责人： 年 月 日 机械加工工艺过程卡片 零件号 零件名称 CA6140车床手柄座 工序号 工序名称 设备 夹具 刀具 量具 工时（min） 名称 型号 名称 规格 名称 规格 名称 规格 Ⅰ 铣，半精铣凸台端面 立式铣床 X51 专用夹具 高速钢端铣刀 25 Ⅱ 钻，扩，铰内孔 立式钻床 Z535 专用夹具 高速钢锥柄麻花钻扩孔钻铰刀 游标卡尺 Ⅲ 钻，粗铰，精铰孔 立式钻床 Z525 专用夹具 高速钢锥柄麻花钻，铰刀 游标卡尺 Ⅳ 钻，铰φ13mm孔 立式钻床 Z525 专用夹具 麻花钻头 Ⅴ 钻φ8.5mm底孔 立式钻床 Z525 专用夹具 Ⅵ 钻粗铰精铰孔 立式钻床 Z525 专用夹具 高速钢锥柄麻花钻，铰刀 卡盘 Ⅶ 钻圆锥孔 立式钻床 Z525 专用夹具 高速钢麻花钻 Ⅷ 钻槽底通孔 立式钻床 Z525 高速钢麻花钻 Ⅸ 拉键槽6H9mm 专用夹具 Ⅹ 钻底孔，攻螺纹M10mm 立式钻床 Z525 专用夹具 高速钢锥柄麻花钻,丝锥 卡盘 Ⅺ 终检 Ⅻ ⅩⅢ 南京理工大学泰州科技学院 毕业设计(论文)外文资料翻译 系　　部： 机械工程系 专 业： 机械工程及自动化 姓 名： 陈游 学 号： 05010113 (用外文写) 外文出处： http://www.mapeng.net 附 件： 1.外文资料翻译译文；2.外文原文。 指导教师评语： 签名： 年 月 日 注：请将该封面与附件装订成册。 附件1：外文资料翻译译文 车床与铣削加工 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，某些机床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。 很早就已经有了车床。现代车床可以追溯到大约17世纪，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。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。它通常是由经过正火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，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。主轴孔的大小是车床的一个重要尺寸，因为当工件通过主轴孔供料时，它确定了能够加工棒料毛坯的最大外径尺寸。 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器件就可以锁定或松开卡盘和花盘。 主轴由电动机经V带或无声链装置提供动力。大多数现代车床都装有5—15马力的电动机，为硬质合金和金属陶瓷合金刀具提供足够的动力，进行高速切削。 尾座组件主要由三部分组成。底座与床身的内侧导轨配合，并可以在导轨上做纵向移动，底座上有一个可以使整个尾座组件夹紧的装置。尾座安装在底座上，可以沿键槽在底座上横向移动，使尾座与主轴箱中的主轴对正并为切削圆锥体提供方便。尾座组件的第三部分是尾座套筒，它是一个直径通常在2～3英寸之间的钢制空心圆柱轴。通过手轮和螺杆，尾座套筒可以在尾座体中纵向移入和移出几英寸。活动套筒的开口一端具有莫氏锥度，可以用于安装顶尖或其他刀具。通常在活动套筒的外表面刻有几英寸长的刻度，以控制尾座的前后移动。锁定装置可以使套筒在所需要的位置上夹紧。 拖板组件用于安装和移动切削工具。拖板是一个相对平滑钓H形铸件，安装在床身外侧导轨上，并可在上面移动。大拖板上有横向导轨，使横向拖板可以安装在上面，并通过丝杠使其运动，丝杠由一个小手柄和刻度盘控制。横拖板可以带动刀具垂直于工件的旋转轴线切削。 铣削加工 铣削是机械加工的一个基础方法。在这一加工过程中，当工件沿垂直于旋转刀具轴线方向进给时，在工件上去除切屑从而逐渐地铣出表面。有时候，工件是固定的，而刀具处于进给状态。在大多数情况下，使用多齿刀具，金属切削量大，只需一次铣削就可以获得所期望的表面。在铣削加工中使用的刀具称做铣刀。它通常是一个绕轴线旋转并且周边带有同间距齿的圆柱体，铣刀齿间歇性接触并切削工件。在某些情况下，铣刀上的刀齿会高出圆柱体的一端或两端。 由于铣削切削金属速度很快，并且能产生良好的表面光洁度，故特别适合大规模生产加工。为了实现这一目的，已经制造出了质量一流的铣床。并且在机修车间和工具模具加工中也已经广泛地使用了非常精确的多功能通用的铣床。车间里拥有一台铣床和一台普通车床就能加工出具有适合尺寸的各种产品。 铣削操作类型：铣削操作可以分成两大种类，每一类又有多种类型。 1．圆周铣削在圆周铣削中，使用的铣刀刀齿固定在刀体的圆周面上，工件铣削表面与旋转刀具轴线平行，从而加工表面。使用这种方法可以加工出平面和成型表面，加工中表面横截面与刀具的轴向外轮廓相一致。这种加工过程常被称为平面铣削。 2．端面铣削铣削平面与刀具的轴线垂直，被加工平面是刀具位于周边和端面的齿综合作用形成的。刀具周边齿完成铣削的主要任务，而端面齿用于精铣。 圆周铣削和端面铣削的基本概念，圆周铣削通常使用卧式铣床，而端铣削则既可在卧式铣床又可以在立式铣床上进行。 铣削面的形成：铣削时可以采用两种完全不同的方法。应注意的是，在逆向铣削时，铣刀旋转方向与工件进给方向相反，而在顺铣时铣刀旋转与工件进给方向相同。在逆铣过程中，当铣刀齿刚切人工件时，切屑是非常薄的，然后渐渐增厚，在刀齿离开工件的地方，切屑最厚。在两种铣削方法中，切屑的形成是不同的，逆铣过程中，刀具有推动使工件从工作台提升的趋势，这种作用有助于消除铣床工作台进给螺杆和螺母间的间隙，从而形成平稳的切削。然而，这种作用也有造成工件与夹紧装置之间的松动的趋势，这时应施加更大的夹紧力。此外，铣削表面的平整度主要取决于切削刃的锋利程度。 顺铣时，最大切屑厚度产生于靠近刀具与工件接触点处。由于相对运动把工件拉向铣刀，如果采用顺铣法，要消除工作台进给时螺杆可能产生的松动。因此，对于不能用于顺铣的铣床，应不采用顺铣方法。因为在铣刀结束切削时，处于切线方向的被切材料发生屈服，所以与逆铣相比，顺铣的被加工表面没有什么切痕。顺铣的另一个优势是切削力趋于将工件压紧在工作台上，因此对工件的夹紧力可以小于逆铣。这一优势可以用于铣削较薄的工件或进行强力切削。顺铣的弱点是铣刀齿刚一切削每片铁屑时，刀齿会撞击工件的表面。如果工件表面坚硬，像铸件，就会使刀齿迅速地变钝。 铣刀 铣刀分类有多种方法，一种方法是根据刀具后角将铣刀分为两大类： 1．仿形铣刀每个刀齿在切削刃的背面磨了一个很小的棱面形成后角，切削刃可以是直线或曲线的。 2．凸轮形后角铣刀每个齿的横截面在切削刃的背面呈偏心曲线状，以产生后角。偏心后角的各面与切削刃平行，具有切削刃的相同形状。这种类型的铣刀仅需磨削齿的前刀面就可以变得锋利，只要切削刃的外形保持不变，铣刀的另一种分类方法是根据铣刀安装的方法进行分类。心轴铣刀带有一个中心孔以使铣刀安装在心轴上。带柄铣刀有一锥柄或直柄轴，含锥形轴柄的铣刀可以直接安装在铣床的主轴上，而直柄轴的铣刀则是夹持在卡盘里。平面铣刀通常用螺栓固定在刀轴的末端上。 根据这种分类方法，通用型的铣刀可分类如下： 心轴铣刀：圆柱形铣刀，角度铣刀，侧刃铣刀，嵌齿铣刀，错齿铣刀，凸轮形后角铣刀，开槽铣刀，高速切削刀。 带柄铣刀：端面铣刀，T形槽铣刀，整体式铣刀，半圆键座铣刀，套式铣刀，高速切削刀，空心铣刀。 铣刀的类型圆柱形铣刀是在圆周上有直的或螺旋形的齿的圆柱形或盘形铣刀。它们可以用来铣削平面，这种铣削称做平面铣削。螺旋形的铣刀上的每个齿是逐渐地接触工件，在给定的时间内，一般有多齿进行铣削，这样可以减少震动，获得一个较平滑的表面。因此，与直齿铣刀相比，这种类型的铣刀，通常使用得更多。 侧刃铣刀的齿除了在圆柱刀体的一端或两端向径向延伸之外，与圆柱形铣刀是相似的。侧刃铣刀的刀齿既可以是直线的，也可以是螺旋形的，这种铣刀一般较窄小，具有盘形的形状。在跨式铣削加工中，常常将两个或更多的侧刃铣刀同时相间地安装在一个刀杆上同步并行切削。 双联槽铣刀是由两个侧刃铣刀组成，但是在铣槽时，作为一组铣刀进行操作。在两个铣刀之间添加一些薄垫片，以调整之间的间距。 错齿铣刀是较薄的圆柱形铣刀，刀上有相互交错的刀齿，相邻刀齿具有相反的螺旋角。这种铣刀经研磨后仅用于周铣，在每个齿突出的一边，留有供切屑排出的缝隙。这种类型的铣刀可用于高速切削，在铣削深槽时可以发挥独特的作用。 开槽铣刀是一种薄型的圆柱形铣刀，厚度一般为1／32—3／16英寸。这种铣刀的侧面呈盘状，有间隙，可以防止粘连。与圆柱形铣刀相比，这种类型的铣刀每英寸直径上的齿数更多，通常用于铣削较深的、狭窄的槽，并可用于切割加工。 附件2：外文原文（复印件） LATHE AND MILLING 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 long long age. 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 changegear system that could connect the motions of the spindle and lea&crew and thus enable threads to be cut.Lathe Construction. The essential components of a lathe are depicted in the block diagram. These are the bed, headstock assembly, tailstock assembly, carriage assembly, 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 sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some 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 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, 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 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. 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 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 because it determines 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 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 modem 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 pemfits aligning the tailstock and headstock spindles and provides a method of tuming tapers. The third major component of the assembly is the tailstock quill. This is a hollow steel cylinder, usually about 2 to sinches in diameter, that can be moved several 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 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 reianvely fiat H-shaped casting that rests and moves on the 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 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 base, 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 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. MILLING 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 teeth that intermittently engage and cut the workpiece. 1 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 jobshop 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. 2. 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 face of the cutter. 2 The major portion of the cutting is done by the peripheral portions of the teeth with the face portions providing a finishing action. The basic concepts of peripheral and face milling are illustrated in Fig. 16-1. 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 Mimng. Surfaces can be generated in milling by two distinctly different methods depicted in Fig. 16-2. Note that in up milling the cutter rotates againsi the direction of feed the workpiece, whereas in down milling the rotation is in the same direction as the feed. As shown in Fig. 16-2, 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, becoming a maximum where the tooth leaves the work. The cutter tends to push the work along and lift it upward from Tool-work relationshios in peripheral and face milling 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 cecum 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. Inasmush 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 considerable 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. 3 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. Milling 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-reheved 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. The common types of milling cutters, classified by this system are as follows: Types of Milling Cutters. Hain 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 plai n 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 simultaneous, 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 particnlarly effective in milling deep slots.