What is the first difference between aerospace and commercial fasteners? Carmen Vertullo asked an International Fastener Expo conference.  

“They look different,” Vertullo declared.

“They may have gold and are priced like gold,” he added. If a type of commercial fasteners cost $9 a hundred, aerospace may cost $9 each.

Vertullo, of Aim Testing Laboratory, said even if you don’t sell aerospace fasteners, it is worth your time to understand the differences.

Vigorous inspection and testing lead to higher quality for the higher price, he noted. There is a lot of torque testing.

Most aerospace fasteners are of higher strength and may be made of exotic metals. There are special coatings.  

They are made to National Aerospace Standards. The NAS standards are developed by the aerospace industry and include a full range of parts, including bolts, rivets, washers, screws, nut plates, pins, knobs, etc. Web: aia-aerospace.org/standards/

Aerospace fasteners use UNJF threads.

Aerospace fasteners “always have the part number on them.”

Additional differences:

  • Limited sources: Can be supplied only by manufacturers  on the Defense Logistics Agency’s Qualified Suppliers List (QSLN). That leads to a strong supply chain relationship, Vertullo added. Web: dla.mil/TroopSupport/IndustrialHardware/Engineering-and-Technical-services/Qualified-Suppliers-List/
  • Raw material supply also is controlled with lot traceability.
  • Long lead times.
  • Special features – including “cool features,” Vertullo observed.
  • Special drives.
  • Reusability. An Air Force jet engine may be removed, but the part-numbered fasteners reused, Vertullo recalled from his days as an Air Force jet engine mechanic.
  • Special packaging to prevent dinged or damaged fasteners. “There may be a thread protector on each fastener,” Vertullo pointed out.

An aerospace Hex Head fastener may be lighter than its commercial equivalent. Weight in an airplane is “very important,” Vertullo declared.

It may have lock wire holes, cotter pin holes and Fillister head. Fasteners used in shear bolts may hold the load through the body. Web: AimTestLab.com