Steel rod pole pieces are usually made from a high carbon steel alloy and can conduct magnetic fields easily to the strings. A high carbon steel is best suited for conducting the magnetic field to the strings. Steel with high carbon needs to be plated with chrome, nickel or gold plating to keep the parts from rusting. When manufacturing parts and the plating thickness needs to be taken into consideration not to make the OD of the parts out of spec where it might fit to tightly in the bobbin or flatwork. The stud or steel rod pole pieces are usually faced and have a slight chamfer before being cut off. This will also help when pressing the parts into a tight bobbin and the slight chamfer or radius on the corners helps when assembling parts in a bobbin.