Which type of key is designed to fit into precision grooves cut into a shaft?

• A. Taper key
• B. Sunk key
• C. Feather key
• D. Woodruff key

Answer: (B)

The correct answer is identified as the sunk key. Sunk keys are specifically designed to fit into precision grooves cut directly into a shaft and a corresponding groove in the hub of the component being mounted, such as a pulley or gear. This design allows for a very secure fit and helps to ensure proper alignment and torque transmission between the shaft and the attached components.

Sunk keys are typically rectangular or square in shape and are often set flush with the surface of the shaft, which keeps the overall profile clean and reduces the risk of interference with other components. This feature makes them suitable for applications where precision and compactness are paramount.

In contrast, other options like taper keys, feather keys, and Woodruff keys serve different purposes and have different designs. Taper keys are used primarily for applications requiring a wedging action to secure components, so their function and fitting into the shaft are dissimilar to sunk keys. Feather keys, which are flat and used to transmit torque while allowing axial movement, do not fit into grooves like sunk keys. Woodruff keys are semicircular and fit into a circular recess on the shaft, which again differs from the precision groove fit that defines sunk keys.