In engineering word, key is a machine element used to connect a rotating machine element to a shaft. WOODRUFF KEYS are of semicircular shape. The main advantage of WOODRUFF KEYS is elimination of milling near shaft Shoulders. WOODRUFF KEYS are used to improve the concentricity of the shaft for high speed operation. These keys are made up from SAE 1035 carbon steel. They lock pulleys and gears tightly to transmission shafts.