NYLON INSERTS 101 – PART 1 by Bobby D.S. Wright of Tramec Continental-Aero

NYLON GENERAL INFORMATION Continental-Aero suppliers use the DuPont 66 or Zytel 101 resin nylon for all our nylon insert products. Continental-Aero products can be easily traced back by the trademarked Royal Purple Nylon Insert. Other fastener manufacturers have trademarked nylon insert colors; ESNA (Red), Aztech (Orange), Industrial Nut (Blue), SPS/Greer Technologies (Green), Wyandotte (Gray), Automatic Screw Machine Products (Pink), Abbott Interfast (Yellow), Generic (White/Clear). Per the Harvard Industries Publication FSCM 72962, page 62, the working temperature of Dupont 66 or Zytel 101 is: -70°F and 250°F.

WHY WOULD NYLON VISUALLY APPEAR TO FAIL? There are only six (6) visual symptoms on why a nylon insert will appear to have failed: Brittleness – cracking, extremely soft, dust like with white edges where nylon breaks off. Pig tailing – pieces of nylon are curling and/or breaking off as the mating end is protruding through the nylon, like a pig’s tail. Undersized inner diameter of the nylon – nylon mushrooms or expands upward as the mating end protrudes through the nylon. Melting during installation – literally melts. Pops out during installation – the nylon pops out of the nut. Off center – not centered.

WHAT ACTIONS ARE TO BE TAKEN? If any of the symptoms appear, a manual installation using the appropriate sized socket, 3/8 or ½ driver or any other human powered hand tool (i.e., combination wrench, adjustable wrench, pipe wrench, etc.). Manual installation is the practice of “human power” not pneumatic operated tooling. The nylon insert does not have knowledge of what type of installation practice is used (manual or pneumatic), therefore when manually installing and the problem does not replicate the original compliant, then the nylon is conforming and the root cause is the application of installation by the End User.

BRITTLENESS OF NYLON Physical Appearance: cracking, extremely soft, dust like with white edges where nylon breaks off. This is very rare, therefore a picture of an example can not be provided. Possibility of Root Cause: this is the rarest of the six (6), as less than 1% of nylon issues are considered brittle, due to the lowest working temperature of the nylon at -70°. Most likely the issue is that the mating end has a burr or nick on the threads that are cutting into the nylon (see Pig Tailing).

PIG TAILING OF NYLON Physical Appearance: pieces of nylon are curling and/or breaking off as the mating end is protruding through the nylon, like a pig’s tail. Possibility of Root Cause: Approximately 1% of nylon issues are considered pig tailing, however the most likely issue is that the mating end has a burr or nick on the threads that are cutting into the nylon.