In milling, the milling machine is a machine tool used in precision engineering to shape metal parts and other materials into complex forms.
There are two main types of milling machine, both with a horizontal X-Y table. The first, called vertical, has the spindle mounted on a Z axis, so movement along the three axes allows the machine to drill and bore; the horizontal type, on the other hand, has the spindle mounted horizontally, making it somewhat similar to a large circular saw. It is mainly used to cut slots, grooves and continuous pockets.
In addition to these two types of milling machine there are so-called “machining centres”, which have a fixed table and a motorised head that moves along 4 or more axes.
CNC milling machines can achieve precision down to the micron (0.001 mm), although they require special working conditions such as a climate-controlled environment, a solid foundation, thermal probes on the axes and optical scales.
Milling machines are normally very rigid, because they have to absorb the vibrations generated by the spindle head without losing precision. That is why, when machining very hard materials or at very high speeds, special lubricants are used to optimise tool cooling and reduce cutting forces.