Machining is any process in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. These controlled material removal processes are today collectively known as subtractive manufacturing, which differs from processes of controlled material addition, which are known as additive manufacturing. Exactly what the “controlled” part of the definition implies can vary, but it almost always implies the use of machine tools (in addition to just power tools and hand tools).
CNC Machining is a process used in the manufacturing sector that involves the use of computers to control machine tools. Tools that can be controlled in this manner include lathes, mills, routers, and grinders. The CNC in CNC Machining stands for Computer Numerical Control.
There are many kinds of machining operations, each of which is capable of generating a certain part geometry and surface texture.
In turning, a cutting tool with a single cutting edge is used to remove material from a rotating workpiece to generate a cylindrical shape. 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.
Drilling is used to create a round hole. 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.
In boring, a tool with a single bent pointed tip is advanced into a roughly made hole in a spinning workpiece to slightly enlarge the hole and improve its accuracy. It is a fine finishing operation used in the final stages of product manufacture.
Reaming is one of the sizing operations that removes a small amount of metal from a hole already drilled.
In milling, a rotating tool with multiple cutting edges is moved slowly relative to the material to generate a plane or straight surface. The direction of the feed motion is perpendicular to the tool’s axis of rotation. The speed of motion is provided by the rotating milling cutter. The two basic forms of milling are:
- Peripheral milling
- Face milling
Other conventional machining operations include shaping, planing, broaching and sawing. Also, grinding and similar abrasive operations are often included within the category of machining.