What is the function of a thread gauge in fastener inspection?

• A. To measure torque applied to a bolt
• B. To verify thread pitch and thread form to ensure compatibility with fasteners and holes
• C. To assess thread engagement length
• D. To check bolt diameter tolerance during drilling

Answer: (B)

A thread gauge is used to verify thread pitch and thread form so the fastener will properly mate with its nut or hole. The gauge checks that the distance between threads (the pitch) and the thread profile match the standard for that size, ensuring compatibility and a secure fit. If the gauge passes, the threads are within tolerance and should screw together smoothly; if it fails, the threads may cross‑thread or not engage correctly. This is distinct from measuring torque, which uses a torque wrench, or from assessing engagement length or diameter tolerance, which involve depth checks or calipers/micrometers rather than thread form verification.