Around the middle of the 19th century, the latter words were coined as the concepts that they described evolved into widespread existence. In current usage, the term “machining” without qualification usually kalpakjian manufacturing engineering and technology pdf free the traditional machining processes. Turning operations are operations that rotate the workpiece as the primary method of moving metal against the cutting tool.
Lathes are the principal machine tool used in turning. Milling operations are operations in which the cutting tool rotates to bring cutting edges to bear against the workpiece. Milling machines are the principal machine tool used in milling. Drilling operations are operations in which holes are produced or refined by bringing a rotating cutter with cutting edges at the lower extremity into contact with the workpiece. Drilling operations are done primarily in drill presses but sometimes on lathes or mills. Burnishing produces no swarf but can be performed at a lathe, mill, or drill press.
An unfinished workpiece requiring machining will need to have some material cut away to create a finished product. For example, a workpiece may be required to have a specific outside diameter. A lathe is a machine tool that can be used to create that diameter by rotating a metal workpiece, so that a cutting tool can cut metal away, creating a smooth, round surface matching the required diameter and surface finish. A drill can be used to remove metal in the shape of a cylindrical hole. Although a machine shop can be a stand-alone operation, many businesses maintain internal machine shops which support specialized needs of the business. Machining requires attention to many details for a workpiece to meet the specifications set out in the engineering drawings or blueprints.
Beside the obvious problems related to correct dimensions, there is the problem of achieving the correct finish or surface smoothness on the workpiece. Frequently, this poor surface finish, known as chatter, is evident by an undulating or irregular finish, and the appearance of waves on the machined surfaces of the workpiece. To perform the operation, relative motion is required between the tool and the work. This relative motion is achieved in most machining operation by means of a primary motion, called “cutting speed” and a secondary motion called “feed”. The shape of the tool and its penetration into the work surface, combined with these motions, produce the desired shape of the resulting work surface. There are many kinds of machining operations, each of which is capable of generating a certain part geometry and surface texture. The primary motion is provided by rotating the workpiece, and the feed motion is achieved by moving the cutting tool slowly in a direction parallel to the axis of rotation of the workpiece.
It is accomplished by a rotating tool that typically has two or four helical cutting edges. The tool is fed in a direction parallel to its axis of rotation into the workpiece to form the round hole. It is a fine finishing operation used in the final stages of product manufacture. The direction of the feed motion is perpendicular to the tool’s axis of rotation. The speed motion is provided by the rotating milling cutter.