Drilled head/shank bolts are used in what scenario?

• A. Used where external safetying is required
• B. Used for fastest assembly
• C. Used for corrosion resistance
• D. Not used in structural applications

Answer: (A)

These bolts are designed to be secured with a safety wire, which is the main idea behind using drilled head or drilled shank bolts. The hole through the head or shank allows a wire to pass through and be anchored to the surrounding structure, creating a positive lock that prevents the bolt from backing out in high-vibration or safety-critical applications. That’s why they’re used where external safetying is required: the safety wire provides an additional retention mechanism beyond just friction from the threads. They’re not chosen for the fastest assembly, since threading and wiring add steps, and the feature isn’t about corrosion resistance—that depends on material or coatings rather than the hole. They can indeed be used in structural applications, especially when preventing loosening is essential, so the idea that they aren’t used structurally isn’t correct.