🔍 Key Concepts

• Coupling hubs are usually secured to shafts with set screws that tighten against a flat or key on the shaft. • For rotating equipment, protruding bolt heads on the hub are generally undesirable because of balance and safety. • Compare which figure shows a headless, fully threaded fastener designed to be recessed into the hub rather than pass completely through and stick out.

💭 Think About

• Which of the options would sit completely within a threaded hole in the hub and press against the shaft, instead of clamping two parts together with a head and nut? • Which figure shows a fastener that is short, fully threaded, and has no conventional head that would project from the rotating coupling? • Among B, C, F, and H, which one is specifically shaped to act as a set screw in a rotating shaft application rather than a general-purpose machine screw or pin?

✅ Before You Answer

• Verify which figure is a headless set screw (sometimes called a grub screw) rather than a regular bolt or screw with a head. • Check that the chosen fastener is fully threaded and intended to bear directly on the shaft surface or key. • Confirm that the fastener you choose would not leave a projecting head that could interfere with rotation or require extra clearance around the coupling.