Which key is tapered only on the side that engages the hub and the keyway is tapered?

• A. Flat key
• B. Rounded keys
• C. Plain Tapered keys
• D. Square key

Answer: (C)

A tapered interface between the shaft and hub creates a wedging action that locks the parts together and transmits torque securely. The plain tapered key is designed with a taper on the side that sits against the hub, and it works with a matching tapered keyway in the hub bore. As the key is driven in, the taper causes the contact to tighten along the mating faces, pulling the hub firmly onto the shaft and increasing friction to prevent slipping. The other side remains flat to fit properly against the shaft.

This wedge fit gives a reliable torque transmission with less chance of play, which is why a plain tapered key is the best choice for a tapered keyway system.