The machining process for crankshafts involves a number of processes, such as heating a billet and then pounding or pressing it into shape. These are the processes involved in producing a forged crankshaft; other production methods involved difference processes.
Most high-performance crankshafts are forged from billets. A billet is a round metal bar. Steel alloys used in most crankshafts provide designers with a desirable blend of properties. For example, medium-carbon alloys contain predominantly iron, but other elements are carefully chosen and blended into the mix to achieve qualities such as hardenability, nitridability, corrosion resistance, tensile strength and other qualities.
After selecting an appropriately sized billet made from a well-suited alloy, the billet is heated to a temperature at which it can be forged. This temperature typically falls in a range between 1,960 and 2,250 degrees Fahrenheit. Forging requires that the billet be either pressed into shape using a die or cast in the negative form of the crankshaft. Often, this requires a series of dies to achieve the complex and intricate shapes required in high-performance crankshafts.
Forging and machining from a round billet requires intensive amounts of machining and design, but it also allows for the greatest possible flexibility. The highest-performing crank shafts simply could not be produced using other methods, such as stamping.