Metal Repair and Panel Replacement
Metal Repair and Panel Replacement
This domain tests hand metalwork and the decision to repair or replace. Expect hammer and dolly, off-dolly, pick and file, shrinking and stretching, stud welding, panel alignment, hem flanges, adhesive bonding, rivet bonding, and weld-through primer. The exam focuses on controlled metal movement and preserving panel strength.
Core rules
- Read the damage: a low crown panel stretches more easily; a sharp crease or stretched area may need shrinking, not just filling.
- Hammer and dolly work should move metal back to shape with controlled blows; use off-dolly for raising low areas and on-dolly for planishing.
- Heat shrinking is used sparingly. On HSS/UHSS, heat may be restricted or prohibited; follow OEM procedures.
- Replace rather than repair when the panel is kinked at a body line, has poor backside access, is torn, or is made of a non-repairable material.
- When replacing, duplicate the OEM joint: spot welds, rivet bonding, adhesives, hem flange, and seam sealer. Clean and prime mating surfaces with weld-through primer where required.
- Check gaps and flushness before final welding or bonding; adjust at hinges, shims, and bolted joints, not by force.
Worked example
A door skin has a shallow dent with stretched metal around the centre. The technician planishes the area, then uses a shrinking disc to tighten the stretched crown. Reasoning: the metal has been stretched by impact, so filling alone would leave a flexible, oil-canning repair. After shrinking, the technician checks the contour with a straightedge and applies a thin filler coat only after the metal is stable. If the skin were creased at the beltline or the intrusion beam were damaged, replacement would be the better decision.
Traps
- Over-shrinking and creating a low spot.
- Using body filler to bridge rust or a tear.
- Heating UHSS to shrink it.
- Forgetting weld-through primer on bonded or welded mating surfaces.
- Aligning a panel by over-tightening bolts and distorting gaps.