CNC milling is a cutting process in which material is removed from a block by a rotating tool. In CNC milling the cutting tool is moved in all three dimensions to achieve the desired part shape, the cutting tool usually rotates about an axis that is perpendicular to the table that holds the material to be cut. A milling machine looks somewhat like a drill press at first glance. A cutting tool protrudes down from a rotating spindle. A block of material is placed on a moving table below the cutter. While the cutting tool turns, a computer controls the vertical (Z axis) motion of the cutter and the horizontal (X and Y axis) motion of the block of material. The cutter is guided to move through the material, removing portions to create shapes.

Additionally, the material can be turned to various orientations in the middle of the process and cutting tools of various shapes can be used. Material is usually removed by both the end and the side of the cutting tool. Some common cutter shapes include:
Plain endmill - used for most milling - creates walls with straight 90 deg edges and sharp corners at the bottom of recesses.

Chamfer endmill - creates 45 deg bevels on the top edge of a wall or recess

Grooving endmill - creates rectangular grooves in side walls

Ball mill - creates rounded edges at the bottom edge of a recess

Rounding endmill - creates rounded edges at the top edge

Angle endmill - creates walls at angles other than 90 deg

and, not shown, a conventional drill

CNC Milling has several advantages over other manufacturing processes. It is cost effective for short runs. Complex shapes and high dimensional tolerances are possible. Smooth finishes can be achieved. CNC milling can produce almost any 2D or 3D shape provided that the rotating cutting tools can reach the material to be removed. Examples of CNC milled parts include engine components, mold tooling, complex mechanisms, enclosures, etc.

Computer Numerical Control (CNC) Milling, the most common form of CNC, is a cutting process for precision high speed milling to cut cavities and cores, gears, inserts, sub-inserts, mold bases and other metal components.
CNC milling provides computer-driven accuracy to produce components that only a few years ago would have been virtually impossible with hand milling

CNC also allows for precise repeatability of multiple copies

Once programmed, the High Speed CNC Milling Machine can operate unattended, reducing production costs related to labor