Making the blanks
Depending on the alloy required, the appropriate metals are melted in the necessary proportions in a furnace. The metal is then extracted from the furnace in the form of a continuous strip, which is cut to produce coils weighing up to 2.8 tonnes.
The strip is passed through powerful rolling mills to reduce it to the thickness of a coin. Blank discs of metal are then punched from the strip in a blanking press at a rate of up to 10,000 a minute.
Rolling metal under great pressure makes it hard so the blanks have to be softened, something which is achieved by heating them in an annealing furnace at up to 950°C. The blanks are then cleaned to ensure that they are free from any blemishes.
Making the dies
Once a design has been approved, a plaster model is prepared at several times the diameter of the intended coin. The plaster model is scanned by a ruby-tipped probe which records the design as a digital file on a computer. Guided by this digital file, an engraving machine cuts the design into a piece of steel at the correct size of the coin. Known as a reduction punch, this piece of steel is then used to make the dies which will actually strike the coins.
Striking the coins
For the final stage of the process, the blanks are fed into a coining press containing a pair of dies. Applying a pressure of around 60 tonnes, the dies strike the blanks and turn them into coins at speeds of up to 850 a minute.