What condition do torque values for tightening aircraft nuts and bolts typically refer to?

Torque values for tightening aircraft nuts and bolts typically refer to clean, dry threads. This standardization is important because the friction present between the mating surfaces can significantly affect the torque reading.

When threads are clean and dry, the friction is predictable, allowing for accurate torque application to achieve the necessary clamping force. This condition ensures that the torque values provided in maintenance manuals and guidelines can be consistently applied for reliable assembly and safety.

In contrast, if the threads are lubricated, wet, or corroded, it can alter the resistance encountered during tightening, leading to inaccurate torque application. For instance, lubricated threads would reduce friction and potentially result in overtightening if the torque is applied as specified for dry threads. Similarly, corroded threads can create unpredictable friction conditions, leading to the failure to achieve the desired clamping force. Coated or treated threads may also not align with the generic torque references unless specified otherwise, as the coating material can further influence friction and torque requirements.