Fasteners and Body Construction
Fasteners and Body Construction
The exam tests how bodies are assembled and how fasteners are selected, torqued and replaced. It links construction type to collision repair decisions.
Core rules
- Body types: body-on-frame (separate chassis), monocoque/unibody (stressed panels), and space frame (tubular or extruded members).
- Fasteners include bolts, nuts, self-tapping screws, blind rivets, solid rivets, rivet nuts, clips and adhesive bonds; each has a specified torque or replacement rule.
- Torque-to-yield bolts stretch when tightened and must not be reused; use a calibrated torque wrench and the specified sequence.
- Thread pitch and grade matter: a metric 8.8 bolt is not interchangeable with 10.9 or with an imperial thread.
- Monocoque panels carry load, so a welded or bonded panel is structural, while a bolted wing is cosmetic.
- Crumple zones absorb energy; the passenger cell must stay intact.
Worked example
A front wing is bolted on. Reasoning: the wing is cosmetic, so remove the bolts, disconnect the side repeater, align the gaps, and torque the bolts to the maker's figure. If the wing were bonded or spot-welded into the monocoque, the repair would be structural and would need the specified weld or adhesive.
Traps
Reusing torque-to-yield bolts, over-tightening a plastic clip, and assuming every panel is cosmetic. Candidates also mix metric and imperial threads, and forget that rivet holes must match the rivet diameter, not be drilled oversize.