Fasteners_01_Introduction

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

  • For critical ground support and flight equipment, it is essential to use high quality, tested fasteners from trusted and approved manufacturers
  • All fasteners used on spaceflight hardware shall be selected so that they are controlled by government or industry specifications that include design, performance, and quality assurance requirements
  • Selection of Metallic Materials should demonstrate adequate Stress, Corrosion, and Cracking Resistance in the intended environments
  • Ideally, fasteners are procured in lots. Lots should never be mixed. Certificates of Conformance may also be requested or even required

Test Reports

  • Manufacturer’s test reports should be included with each fracture-critical, low-risk, and fail safe fastener purchased along with all rivets, shear pins, inserts, and retention devices (such as cotter pins, hitch pins, safety wires, and ties)

Traceability

  • Retain and/or develop fastener traceability documentation as relevant and required

Audits and Storage

  • If the fastener manufacturer is under contract for production of fasteners, then a prearranged audit of the supplier may be required as determined by the contracting agency
  • Fasteners shall be maintained in storage according to program requirements until issued for use

COTS

  • For ease, simplicity, and cost advantages, COTS fasteners may be purchased and used as long as all requirements and specifications of the program are met

Quality

  • As with any nonconforming (NC) part, an NC form should be filled out for parts that fail or do not meet the intended use or requirements. Failure Review Boards (FRBs) should be conducted to determine root cause and path forward for part failure

Screening

Lot Size Sample Size Acceptance Criteria
3 to 50 2 0 failures
51 to 100 3 0 failures
101 to 500 5 0 failures
501 to 1200 6 0 failures
1201 and over 7 0 failures

 

Lot Size Sample Size Acceptance Criteria
4 to 50 3 0 failures
51 to 100 5 0 failures
101 to 500 7 0 failures
501 to 1200 8 0 failures
1201 and over 9 0 failures
  • Fasteners should be screened upon arrival for conformity
  • Recommended Sample Selection is shown below for approved manufacturers
  • Recommended Sample Selection is shown below for non-approved manufacturers