Name the 3 parts which make up a key fastener.

• A. Key, Seat, Hub
• B. Key, Key Seat-Shaft, Key Seat-Hub
• C. Key Stock, Shaft, Hub
• D. Key, Key Stock, Hub

Answer: (B)

Torque is transmitted through a keyed connection by three parts: the key itself, and the key seats (keyways) cut into both the shaft and the hub. The key fits into these matching slots on the shaft and on the hub, locking the two parts together so they rotate as one and can transfer torque. This arrangement requires both keyways to exist on the shaft and the hub; without them, the key cannot seat properly and torque cannot be transmitted. The other options either omit one of the needed keyways or refer to something like raw material or unrelated components, which don’t create the locked connection that a keyed fastener provides.