Key stock is used to transmit torque from various components to a rotating shaft. One type of key stock, a machine key, is used for very specific metalworking applications. Machine keys are available in many thickness and weights. A square key is a type of parallel key, is used with rotating shafts and attaching gears. We also carry oversized key stock, step key stock, undersized key stock, and woodruff key stock for all your machinery key needs.