Fasteners_04_Summary

  • Fastener: An item such as a bolt (could be a tensile or shear bolt, shoulder bolt, screw, HiLok®, HiTigue®, or lockbolt), nut, nut plate or anchor nut, rivet, shear pin, helical or cylindrical insert, setscrew, washer, safety wire, cotter pin, etc., which joins or retains components or structural elements.
  • Selection and Procurement, Test Reports, Traceability, Audits and Storage, COTS, and Quality are all very important when working with fasteners
  • Design of nuts, bolts, and rivets may at first appear like a trivial task, but many considerations must be taken into account. These considerations range from but are not limited to shock, vibration, shear, temperature, corrosion, fatigue, stress load (axial, radial), etc.
  • Materials: Most bolts are made from carbon steel, alloy steel, or stainless steel
  • Coating: For most aerospace applications, cadmium coating is used for carbon and alloy steel. Coating is normally not required for stainless steel
  • Lubricants: Used to coat threads. Normally are oil, grease, wax, graphite, or molybdenum disulfide
  • Embrittlement: When free hydrogen is present near metal, embrittlement of the metal may occur.
  • Locknuts: Used to bind the nut thread to the bolt thread. In aerospace applications, the deformed thread locknut is common due to ease of manufacturing, reuse and use in a high range of temperatures
  • Locking Adhesives, such as Loctite may be used
  • Washers: Generally used to ensure a uniform tension load on the bolt
  • Inserts: Inserts are threaded on the inside diameter and locked with threads on the outside diameter.
  • Threads: Thread information can be found in the supplemental information entitled “Thread and End Connection Identification Guide”
  • Rivets: Low-cost, permanently installed fasteners that are lighter and bolts
  • Lockbolts: High strength fastener that has either a swaged collar or a type of threaded collar to lock it in place
  • Corrosion: Always consider corrosion possibilities
  • Determining the correct torque is the most difficult part of fastener installation
  • Multiple standards, specifications, and procedures should be used when working with fasteners