机床(00001).doc

附录附录 1英文原文 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 ofa ductile workpiece in the form ofa severely deformed chip. The chip isa 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. Ifa rough cylindrical workpiece revolves about a central axis and the tool rates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. Ifa hollow tube is machined on the inside ina similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning, if the tool point travels ina path of varying radius, a contoured surface like that ofa bowling pin can be produced; or, if the piece is short enough and the support is sufficiently rigid, a contoured surface could be produced by feeding a shaped tool normal to the axis of rotation. Short tapered or cylindrical surfaces could also be contour formed. Flat or plane surfaces are frequently required. They can be generated by radial turning or facing, in which the tool point moves normal to the axis of rotation. In other cases, it is more convenient to hold the workpiece steady and reciprocate the tool across it ina series of straight-line cuts with a crosswise feed increment b