Materials, Fasteners and Joining Methods
Materials, Fasteners and Joining Methods tests your knowledge of body-shop materials and how components are attached or joined. Questions cover mild steel, high-strength steel, aluminium, galvanised sheet, plastics and composites, plus bolts, rivets, clips, adhesives, sealers and welding.
Core rules
- Identify the material before cutting or welding. High-strength steel may require controlled heat; aluminium needs separate tools to avoid galvanic contamination.
- Remove galvanising from weld zones, weld with suitable fume extraction and restore the coating afterwards.
- Use the specified fastener: graded bolts for structural joints, blind rivets for non-structural panels and structural adhesive where specified.
- Match rivet grip length to total material thickness; too short will not form a proper tail, too long will leave a loose joint.
- Clean and prime mating surfaces; isolate dissimilar metals with a barrier to prevent galvanic corrosion.
- Follow torque values and tightening sequences; some bolts are torque-to-yield and must not be reused.
Worked example
A replacement aluminium outer panel is to be fixed to a steel inner structure. Welding is unsuitable because heat distorts the panel and dissimilar metals promote corrosion. The correct approach is to use the specified structural adhesive and/or blind rivets, apply an isolation barrier between steel and aluminium, and seal edges. Reasoning: the joint must carry the intended load without heat damage or galvanic attack.
Traps
Do not mix stainless and mild-steel fixings in a wet area. Do not use ordinary pop rivets where structural rivets are specified. Do not assume all body bolts can be reused.