Which series is mostly used for aircraft threads?

The National Fine Series (NF) is predominantly used for aircraft threads due to its specific design characteristics that provide advantages in aeronautical applications. NF threads have a finer pitch compared to coarse threads, which allows for tighter tolerances and improved resistance to vibration loosening, a crucial factor in the demanding environments faced by aircraft.

Using finer threads also means that the fasteners can be installed with a more precise fit, which is essential for structural integrity and safety in aviation. This provides a better grip and enhances the strength of the connection under various operational conditions, such as extreme temperatures and loads, found during flight.

While coarse series and other thread types exist, they are less commonly used in aircraft applications because they may not offer the same level of vibration resistance or precision fitting that is necessary for the reliable performance of aircraft components. As a result, the National Fine Series is the preferred choice for ensuring optimal performance and safety in aviation environments.