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Question

Difficulty: MediumSpecialty Fasteners and Anchors

An automotive technician is reassembling a front suspension tie-rod end and must ensure that the retaining fastener cannot back off under severe road vibration. Which specialty fastener combination features slotted cutouts designed to receive a locking pin inserted through a pre-drilled hole in the threaded stud?

  1. A
    Flange nut and roll pin
  2. Castle nut and cotter pinAnswer
  3. C
    Acorn nut and clevis pin
  4. D
    Wing nut and hitch pin

Answer

The castle nut and cotter pin combination is specifically designed to prevent fasteners from backing off under high vibration by positively locking the nut through aligned slots and a drilled stud hole.
A castle nut (castellated nut) is specifically manufactured with perimeter slots at its crown. When torqued onto a drilled stud (such as a tie-rod end or ball joint), a cotter pin is inserted through the aligned slot and hole. Bending the cotter pin's tines around the nut creates a fail-safe mechanical lock that prevents the nut from loosening under continuous vibration.

Step-by-Step Solution

1
Identify the functional requirements of the joint
The application requires a positive mechanical lock on a suspension component subjected to extreme vibration and cyclic loading.
Standard friction-based nuts can loosen over time under severe road vibration, leading to dangerous steering failure.
2
Analyze fastener geometries matching the described features
A castle nut (or castellated nut) contains machined slots (crenels) on its top collar, and a cotter pin (split pin) passes through these slots and a cross-drilled hole in the mating stud.
Once the cotter pin prongs are bent around the nut flats, the assembly forms a physical barrier that prevents any rotational movement of the nut.

Key Concept

Positive mechanical locking fasteners for critical high-vibration automotive linkages
Estimated Time:45s
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Topics

Specialty Fasteners and Anchors

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