【正文】 toward an increasing application of metal forming processes. However, die costs and the capital cost of machines remain rather high。 0. 125mm is economical on both diameter and length of turn. Metalcutting processes are extensively used in the manufacturing industry. They are characterized by the fact that the size of the original workpieee is sufficiently large that the final geometry can be circumscribed by it, and that the unw anted material is remo ved as chips, particles, and so on. The chips are a necessary means to obtain the on some parts. Bores and singlepoint finishes can be held to 177。t in the economy of the parts machined on the automatic screw less than 1 000 parts may be more economical to set up on the turret lathe than on the automatic screw machine. The cost of the pans machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities. Since surface roughness depends greatly upon material tumed, tooling, and feeds and speeds employed,minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances. In some cases, tolerances of 177。 Applying this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating. In designing for low quantities such as 100 or 200 parts, it is most economical to use the turret lathe. In achieving the optimum tolerances possible on the turret lathe, the designer should strive for a minimum of operations. Generally, automatic screw machines fall into several categories。s fingertips with production speeds on a par with the fastest processing equipment on the scene today. Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tole rances of an experimental part that has been produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used. Production machining equipment must be evaluated now, more than ever before, in terms of ability to repeat accurately andrapidly. s time is consumed by simple, repetitious adjustments and in watching chips being made. Consequently, to reduce or eliminate the amount of skilled labor that is required, turret lathes, screw machines, and other types of semiautomatic and automatic lathes have been highly developed and are widely used in manufacturing. The engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. Today these lathes are used primarily in small shops w here smaller quantities rather than large production runs are encountered. The engine lathe has been replaced in today39。 8 7 6切削面積也可以用進(jìn)給量 f 和切削深度α表示如下： H1=fsink 及 b=a／ sink 式中 x 為主偏角 (即切削刃與工作平面形成的夾角 )。 ‘ 未變形狀態(tài)的切屑寬度 b，是在與切削方向垂直的平面內(nèi)沿切削刃測(cè)得的切屑寬度。 未變形狀態(tài)時(shí)的切屑厚度 h，就是在垂直于切削方向的平面內(nèi)垂直于切削刃測(cè)量得到的切屑厚度。在鉆削中，切削深度等于鉆頭直徑。切削深度決定工件的最終尺寸。 包含主運(yùn)動(dòng)方向和進(jìn)給運(yùn)動(dòng)方向的平面被定義為工作平面，因?yàn)樵撈矫姘瑳Q定切削作用的兩種基本運(yùn)動(dòng)。對(duì)于銑削，以刀具的每齒進(jìn)給量 fz (mm／ tooth)來(lái)表示， fz 是相鄰兩齒間工件的移動(dòng)距離。進(jìn)給速度 vf 定義為在切削刃的某一選定點(diǎn)上，進(jìn)給運(yùn) 動(dòng)要對(duì)于工件的瞬時(shí)速度。 連續(xù)的切屑切除過(guò)程，從而形成所要求的加工表面。 在主運(yùn)動(dòng)之外，當(dāng)?shù)毒呋蚬ぜ鬟M(jìn)給運(yùn)動(dòng) f 時(shí)，便產(chǎn)生重復(fù)的或根據(jù)具體運(yùn)動(dòng)方式不同， v、 d 和 n 可能與加工材料或工具有關(guān)。 切削速度 v 是主運(yùn)動(dòng)中刀具 (在切削刃的指定點(diǎn) )相對(duì)工件的瞬時(shí)速度。 車削時(shí)，工件的回轉(zhuǎn)運(yùn)動(dòng)是主運(yùn)動(dòng)；龍門刨床刨削時(shí)，工作臺(tái)的直線運(yùn)動(dòng)是主運(yùn)動(dòng)。也就是說(shuō)，刀具與工件材料之間需要兩種相對(duì)運(yùn)動(dòng)。屬于此類加工方法的例子有車削、鉆削、鉸孔、 銑削、牛頭刨削、龍門刨削、拉削、磨削、珩磨和研磨。這個(gè)基本過(guò)程是機(jī)械過(guò)程：實(shí)際上是一個(gè)剪切與斷裂相結(jié)合的過(guò)程。刀具相對(duì)工件運(yùn)動(dòng)，機(jī)械能通過(guò)刀具作用于工件。而且，金屬切削加工的自動(dòng)生產(chǎn)系統(tǒng)的發(fā)展要比金屬成形加工的自動(dòng)生產(chǎn)系統(tǒng)的發(fā)展要快得多。然而，由于金屬成形加工的模具成本和設(shè)備成本仍然很高，因此盡管金屬切削加工的材料消耗較高，在許多情況下，它們?nèi)匀皇亲罱?jīng)濟(jì)的。切屑量多少不一，可能占加工前工件體積的百分之幾到 70％ — 80％不等。 4不需要的材料以切屑、顆粒等形式被去除掉。 金屬切削加工在制造業(yè)中得到了廣泛的應(yīng)用。0． 0125mm。0． 125mm。 0． 05mm。 因?yàn)榱慵谋砻娲植诙仍诤艽蟪潭壬先Q于工件材料、刀具、進(jìn)給量和切削速度，采用自動(dòng)仿形車床加工所得到的最小公差不一