Millingis the machiningprocess of using rotary cuttersto remove materialfrom a workpiece advancing in a direction at an angle with the axis of the tool.It covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes in industry and machine shops today for machining parts to precise sizes and shapes.
Milling can be done with a wide range of machine tools. The original class of machine tools for milling was themilling machine. After the advent of computer numerical control (CNC), milling machines evolved intomachining centers(milling machines with automatic tool changers, tool magazines or carousels, CNC control, coolant systems, and enclosures), generally classified asvertical machining centersandhorizontal machining centers .The integration of milling into turning environments and of turning into milling environments, begun with live tooling for lathes and the occasional use of mills for turning operations, led to a new class of machine tools,multi tasking machines, which are purpose-built to provide for a default machining strategy of using any combination of milling and turning within the same work envelope.
Milling is a cutting process that uses a milling cutter to remove material from the surface of a workpiece. The milling cutter is a rotary cutting tool, often with multiple cutting points. As opposed to drilling, where the tool is advanced along its rotation axis, the cutter in milling is usually moved perpendicular to its axis so that cutting occurs on the circumference of the cutter. As the milling cutter enters the workpiece, the cutting edges of the tool repeatedly cut into and exit from the material, shaving off chips from the workpiece with each pass. The cutting action is shear deformation; the metal is pushed off the workpiece in tiny clumps that hang together to more or less extent to form chips. This makes metal cutting a bit different from slicing softer materials with a blade.
The milling process removes material by performing many separate, small cuts. This is accomplished by using a cutter with many teeth, spinning the cutter at high speed, or advancing the material through the cutter slowly; most often it is some combination of these three approaches. The speeds and feeds used are varied to suit a combination of variables. The speed at which the piece advances through the cutter is called feed rate, or just feed; it is most often measured in length of material per full revolution of the cutter.
There are two major classes of milling process: