CFS CFS Locking & Anti-Vibration Fasteners 2

Question 1

A castle nut (castellated nut) with a cotter pin provides locking by:

Accepted Answer

Positive mechanical restraint — the cotter pin through the bolt hole prevents nut rotation regardless of clamp load

Answer

The cotter pin passes through slots in the castle nut and a cross-drilled hole in the bolt, creating a positive mechanical lock that prevents rotation even under complete loss of preload.

Question 2

Thread-locking adhesives (e.g., anaerobic adhesives like Loctite) cure in the absence of air and presence of metal ions. What property distinguishes a 'medium strength' grade from a 'high strength' grade?

Accepted Answer

Medium strength allows disassembly with standard hand tools; high strength typically requires heat or special tools for removal

Answer

Medium-strength (typically blue) anaerobic adhesives are designed to be disassembled with standard tools, while high-strength (typically red) grades require heat application or significant force to break the bond.

Question 3

Which type of serrated flange fastener provides locking action by biting into the mating surface upon tightening?

Accepted Answer

Serrated (tooth) flange nut

Answer

Serrated flange nuts have radial teeth on the flange bearing surface that bite into the mating material when torqued, creating mechanical locking resistance against vibration-induced loosening.

Question 4

A jam nut (thin nut) used as a locking method works by:

Accepted Answer

Compressing the bolt threads between the two nuts, creating a locked friction grip

Answer

When a jam nut is tightened against a primary nut, the bolt is placed in tension between them and the threads are loaded in opposite directions, creating high friction that resists self-loosening.

Question 5

Wiring (safety wiring) of fasteners is a positive locking method most commonly required in which industry?

Accepted Answer

Aerospace and military aviation

Answer

Safety wiring is mandated in aerospace and military aviation (per MIL-DTL-83519 and AC 43.13) to provide positive locking for critical fasteners that cannot be allowed to loosen in flight.

(CFS) Certified Fastener Specialist Practice Test

(CFS) Certified Fastener Specialist Practice Test

CFS CFS Locking & Anti-Vibration Fasteners 2