The carbon steel key stock has a zinc-plated finish and a standard tolerance. The carbon steel grade provides a good balance of toughness, strength, and machinability. It is magnetic. The zinc plating provides corrosion resistance and a smooth, reflective appearance.
Key stock is used to make a machinery part known as a machine key, which fits into a mating keyway to transmit torque between shafts and hubs or bushings. Rectangular and square key stock shapes are the most common, while step key stock is used for damaged or inconsistent keyways.