Basic Machining Operations and Cutting Technology
Basic Machining Operations
Machine tools have evolved from the early foot-powered lathes of the Egyptians and John Wilkinson's boring mill. They are designed to provide rigid support for both the workpiece and the cutting tool and can precisely control their relative positions and the velocity of the tool with respect to the workpiece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile workpiece in the form of a severely deformed chip. The chip is a waste product that is considerably shorter than the workpiece from which it came but with a corresponding increase in thickness of the uncut chip. The geometrical shape of workpiece depends on the shape of the tool and its path during the machining operation.
Most machining operations produce parts of differing geometry. If a rough cylindrical workpiece revolves about a central axis and the tool penetrates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. If a hollow tube is machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning,

基本加工工序和切削技術(shù)

機(jī)床是從早期的埃及人的腳踏動力車和約翰•威爾金森的鏜床發(fā)展而來的。它們?yōu)楣ぜ偷毒咛峁﹦傂灾尾⒖梢跃_控制它們的相對位置和相對速度?；旧现v，金屬切削是指一個磨尖的鍥形工具從有韌性的工件表面上去除一條很窄的金屬。切屑是被廢棄的產(chǎn)品，與其它工件相比切屑較短，但對于未切削部分的厚度有一定的增加。工件表面的幾何形狀取決于刀具的形狀以及加工操作過程中刀具的路徑。
大多數(shù)加工工序產(chǎn)生不同幾何形狀的零件。如果一個粗糙的工件在中心軸上轉(zhuǎn)動并且刀具平行于旋轉(zhuǎn)中心切入工件表面，一個旋轉(zhuǎn)表面就產(chǎn)生了，這種操作稱為車削。如果一個空心的管子以同樣的方式在內(nèi)表面加工，這種操作稱為鏜孔。當(dāng)均勻地改變直徑時便產(chǎn)生了一個圓錐形的外表面，這稱為錐度車削。如果刀具接觸點(diǎn)以改變半徑的方式運(yùn)動，那么一個外輪廓像球的工件便產(chǎn)生了；或者如果工件足夠的短并且支撐是十分剛硬的，那么成型刀具相對于旋轉(zhuǎn)軸正常進(jìn)給的一個外表面便可產(chǎn)生，短錐形或圓柱形的表面也可形成。
平坦的表面是經(jīng)常需要的，它們可以由刀具接觸點(diǎn)相對于旋轉(zhuǎn)軸的徑向車削產(chǎn)生。在刨削時對于較大的工件更容易將刀具固定并將工件置于刀具下面。刀具可以往復(fù)地進(jìn)給。成形面可以通過成型刀具加工產(chǎn)生。