Welding, Brazing and Cutting for Body Work
Welding, Brazing and Cutting for Body Work tests process selection, settings, joint preparation, distortion control and safe cutting. You must know when to use MIG/MAG, TIG, resistance spot welding, brazing or plasma cutting on body panels.
Core rules
- MIG/MAG is common for steel body panels: match wire diameter, current, wire-feed speed, gas flow and travel speed.
- Clean metal to bare, fit joints closely, tack first and use stitch or back-step welding to limit distortion.
- Use the correct shielding gas; do not weld galvanised steel without removing coating and extracting fume.
- Resistance spot welding needs clean mating surfaces, correct electrode alignment and squeeze time.
- Brazing joins without melting the base metal; it is useful on thin panels but is not a structural substitute unless specified.
- Cutting: use a plasma cutter or cut-off wheel with guards, eye protection and fire watch; never cut into a fuel or brake line.
Worked example
A 1.2 mm mild-steel sill section is to be replaced. The repairer cuts the section to the approved joint, strips coating 20 mm back, fits closely, tacks at intervals, then stitches alternating sides. Current is set low and wire speed matched to avoid burn-through. After welding, the repair is ground, sealed and cavity-waxed. Reasoning: low heat and a balanced sequence control distortion on thin sheet.
Traps
Do not weld over paint, sealer or galvanising. Do not use a cutting torch near a fuel tank. Do not leave gaps that need bridging. Do not forget to disconnect the battery and protect electronic modules before welding.