Woodruff Key, Steel, C 40 to 50 Hardness, SAE-8630

Woodruff keys, also known as half-moon keys, are semicircular shaped keys that, when installed, leave a protruding tab. The keyway in the shaft is a semi-circular pocket and the mating part has a longitudinal slot. They are used to improve the concentricity of the shaft and the mating part, which is critical for high speed operations. The main advantage of the Woodruff key is that avoids the milling of a keyway near shaft shoulders, which already have stress concentrations. Common applications include machine tools, automotive applications, snowblowers and marine propellers.