Understanding machining difficulties in gray iron

Bosch Braking Systems' engineers look more closely than usual at iron brake rotor samples to give new insights into critical characteristics of the material

Gray cast iron, with its easy machinability, good mechanical properties, low material cost, high thermal conductivity, and ready availability, has been an important material in the transportation industry for years. The above characteristics have made gray cast iron the material of choice for many applications in the braking industry.

Brake drums and rotors are machined dry, eliminating coolant and coolant treatment costs. Dry machining can, however, be affected more by microstructural differences between casting batches, known as heats. Cutting tool life varies significantly between heats. The material specification for gray iron is wide, and often heats that are difficult to machine are within specifications.