CFS CFS Locking & Anti-Vibration Fasteners

Question 1

Which of the following best describes the locking mechanism of a prevailing torque nut (e.g., nylon insert lock nut)?

Accepted Answer

It creates friction through a deformed or non-metallic insert that grips the bolt threads independent of clamping load

Answer

It uses a chemical adhesive to bond threads together

Answer

It relies entirely on high clamp load to prevent loosening

Answer

It uses a locking wire threaded through the nut

Question 2

A Belleville (conical spring) washer used as a locking device primarily functions by:

Accepted Answer

Maintaining a residual spring load that compensates for minor clamp load loss due to embedding or relaxation

Answer

Biting into the mating surface with serrations

Answer

Chemically bonding to the bolt shank

Answer

Deforming the bolt threads upon installation

Question 3

Per IFI and industry standards, a nylon insert lock nut (Nylock) should generally NOT be reused after removal because:

Accepted Answer

The nylon insert permanently deforms and loses its interference fit after the first installation

Answer

The nut corrodes after first use

Answer

The threads stretch beyond reuse limits

Answer

Reuse is permitted but requires re-torquing

Question 4

What is the primary difference between free-spinning lock washers and prevailing torque fasteners in a joint assembly?

Accepted Answer

Prevailing torque fasteners create locking resistance throughout tightening and loosening, while free-spinning lock washers only function under clamp load

Answer

Free-spinning lock washers create locking force before the nut contacts the bearing surface; prevailing torque fasteners do not

Answer

Free-spinning lock washers are reusable; prevailing torque fasteners are not

Answer

Prevailing torque fasteners are used only in aerospace; lock washers are used in general industry

Question 5

Which fastener locking method is considered most reliable in high-temperature environments where nylon inserts would degrade?

Accepted Answer

All-metal prevailing torque nut (distorted thread or beam-type)

Answer

Nylon insert lock nut

Answer

Chemical thread-locking adhesive (e.g., Loctite)

Answer

Split lock washer

Question 6

The Junker vibration test (DIN 65151) is used to evaluate fastener locking systems by:

Accepted Answer

Subjecting the joint to transverse (lateral) vibration loads that are most effective at causing self-loosening

Answer

Applying axial tensile load cycles to the bolt

Answer

Immersing the fastener in a salt spray chamber

Answer

Measuring torque-tension relationships under static load