Which of the following best describes the function of lock wire in fastener assemblies?

• A. It secures the fastener against loosening
• B. It accelerates torque loss
• C. It reduces bolt strength
• D. It serves as a fuse

Answer: (A)

Lock wire is used to keep fasteners from turning and losing preload under vibration. It does this by threading the wire through holes in the fastener heads (or between securing points) and twisting it tight so the two parts cannot rotate independently. That tension creates a mechanical lock that resists any loosening, helping maintain the clamp load and torque at the joint. It isn’t intended to speed up torque loss, weaken the bolt, or act as a fuse; its purpose is to prevent loosening and preserve joint integrity.