Torque values for tightening aircraft nuts and bolts generally relate to what type of threads?

The torque values for tightening aircraft nuts and bolts are generally referenced for clean, dry threads. This is because clean, dry conditions provide a standard surface texture and friction level that manufacturers base their torque specifications on. When threads are clean and dry, there is a predictable amount of friction that can be accounted for, ensuring that the fasteners are tightened to the required preload without over-tightening, which could compromise the integrity of the joint or the material.

When using lubrication or coatings, the friction characteristics change, which can require adjusting the torque values to achieve the same level of tension in the fasteners. However, in standard procedures for maintenance and assembly, torque specifications focus on clean, dry threads to ensure consistency and reliability in fastening practices across various applications.