Milling and turning

There are three main methods of shaping metal by a machine in a commercial setting:

A close-up image of a computer numerical controlled (CNC) lathe machine in a workshop.
CNC lathe

Metal can be turned in a lathe, which can be hand operated or controlled via a computer on a computer numerical controlled (CNC) lathe. A lathe spins the work at high speed as a cutting tool is introduced to the metal to produce round and cylindrical shapes. Round pieces of metal are held in a lathe using a three-jaw chuck, and metal that is not round is held by a four-jaw chuck.

A three-jaw chuck, used for holding cylindrical material, alongside a four-jaw chuck, used for cubes and cuboids.

Metal can be shaped using a milling machine - a very versatile tool for smoothing a surface or edge and for cutting grooves and profiles. Milling machines can work either horizontally (horizontal milling machine) or vertically (vertical milling machine) - both machines perform the same tasks; the main difference is the direction the cutting tool is held.

A close-up blurred out image of a computer numerical controlled (CNC) milling machine cutting metal.

If a part is too complex to shape by hand or on a milling machine, it can be cast by melting metal and then pouring it into a mould. It is possible to cast pewter quite easily. The melting point is low, around 200°C, and moulds can be made from laser-cut or hand-shaped medium-density fibreboard (MDF).

Sandcasting can be used to cast larger and more complex shapes as it uses a two-part mould:

  1. a former is made, usually by hand, and is placed in the ‘green’ sand, which is packed tightly around the former before it is removed
  2. this is repeated on the other part of the mould
  3. two holes are made in the sand, one for the molten metal to be poured into (the runner) and one for the metal to come up and out the other side (the riser)
  4. once they are both ready, parting powder is applied to the sand and the two moulds are placed together, one on top of the other
  5. the molten metal, often aluminium in schools, is poured into the runner until it comes up to the riser when the cavity in the sand is full of metal
The sand casting process, showing sand compressed around a former to create one half of a mould and around a runner and riser for the other. These are joined and molten metal is added.