For a clevis bolt that attaches a cable fitting to a control surface horn, how tight should the nut be?

• A. Tight enough to prevent the clevis bolt from turning
• B. Tightened to a standard torque
• C. Very loose
• D. Not tight enough to prevent turning

Answer: (D)

Joints in control linkages must act as hinges that can pivot as the surface moves. The clevis bolt and nut are part of that pivot, and the fitting needs a small amount of free rotation to avoid binding and wear as forces change with direction and vibration. If you tighten the nut enough to stop the bolt from turning, the joint can bind, causing stiffness, misalignment, or accelerated wear in the fitting and horn. The right approach is to tighten just enough to keep the assembly secure but not so tight that it prevents turning, maintaining a smooth pivot through the full range of motion. Use a locking method (like a locknut or cotter pin) to prevent loosening from vibration while preserving the necessary rotation. Standard torque values aren’t the goal here because the priority is allowing movement and avoiding binding, not rigid clamping.