NABTEB Light Vehicle Body Repair common mistakes
NABTEB Light Vehicle Body Repair · Understand the traps and how to avoid them.
When asked to select the correct PPE for a body repair task, candidates choose only an apron or overalls and omit eye protection, hearing protection, or respiratory protection.
Candidates focus on protecting clothes from paint and dirt and underestimate the hazards of flying particles, noise, and solvent vapours; they also confuse general workshop dress with task-specific PPE.
What to do instead
For each task, list the hazards first (impact, dust, fume, noise, chemical splash) and then match PPE to each hazard: safety glasses or goggles, face shield when grinding overhead, hearing protection when using air chisels or grinders, and a suitable respirator when mixing filler or spraying. Practise with a hazard–PPE matrix until it becomes automatic.
Candidates name a tool for a job without stating the correct size, type, or safety check, for example saying 'use a grinder' instead of specifying a 115 mm angle grinder with a depressed-centre wheel rated for the RPM.
Exam questions often ask for the appropriate tool and candidates give a generic answer; they have not learned the relationship between tool specification, abrasive rating, and the material being worked.
What to do instead
Revise tools by function and specification: grinder wheel diameter and maximum RPM, disc backing pad hardness, hammer type (body hammer, shrinking hammer, pick hammer), dolly shape, and torque wrench range. When answering, always include the tool type, size or rating, and one safety check (guard in place, wheel undamaged, correct speed).
Candidates classify steel and aluminium incorrectly, for example stating that galvanised steel can be welded with the same MIG process and settings as mild steel, or that high-strength steel can be heated and straightened freely.
Candidates learn one material (mild steel) and apply it to all metals; they do not distinguish between mild steel, high-strength/low-alloy steel, galvanised steel, and aluminium in terms of weldability, heat sensitivity, and corrosion protection.
What to do instead
Build a material-property table: base metal, common body use, welding process and filler, heat restrictions, and corrosion protection. Learn that galvanised steel requires removing coating from the weld zone and using appropriate fume extraction, that high-strength steel has heat limits set by the manufacturer, and that aluminium needs a dedicated MIG set-up with aluminium filler and a clean, separate wire feed.
Candidates describe removing a welded panel by cutting anywhere across the panel or seam, without locating spot welds, and without planning the cut lines to preserve the adjacent structure.
They think of panel removal as simply 'cutting off' the damaged part and do not visualise the spot weld locations, the panel overlap, and the access needed for the replacement panel.
What to do instead
Before any cut, identify spot welds by stripping paint and using a spot weld cutter or drill of the correct diameter; mark cut lines that leave the original flanges intact for the new panel; support the panel before the final cut. Practise on scrap panels: locate welds, cut, and note how the flange is preserved.
Candidates answer panel alignment questions by saying 'adjust the hinges' without explaining the sequence: align the rear door to the quarter panel first, then the front door to the rear door, then the front fender to the front door and hood.
They memorise that hinges and shims are used but not the order of adjustment, so gaps and flushness remain wrong even after moving parts.
What to do instead
Learn the alignment sequence as a chain: fixed rear reference (quarter panel or rear door) → rear door → front door → fender → hood → bumper. For each step, state the check (gap, flushness, character line) and the adjustment (hinge position, shims, striker). Use a gap gauge and straightedge in practice.
Candidates confuse shrinking and stretching: they say to shrink a stretched panel by hammering on-dolly, or to stretch a low spot by using a shrinking hammer.
The terms are similar and the hammer/dolly combinations are easy to mix up; candidates have not linked the hammering technique to the metal flow it produces.
What to do instead
Memorise the rule: on-dolly hammering stretches (thins) the metal; off-dolly hammering with a pick or shrinking hammer shrinks (thickens) it. Use a shrinking disc or heat shrinking for larger areas. Practise on a scrap panel: mark a stretched area, shrink it, and check flatness with a straightedge.
Candidates describe MIG welding settings by 'turning up the power until it sounds right' rather than selecting voltage, wire feed speed, and gas flow for the material thickness and joint type.
They have seen welding demonstrated but have not learned the setting charts or the effect of wire speed on penetration and bead shape.
What to do instead
Learn to set MIG by thickness: for each common gauge (0.8 mm, 1.0 mm, 1.2 mm), note voltage range, wire feed speed, and gas flow (e.g. 10–15 L/min for mild steel). Recognise defects: too low voltage gives a tall, narrow bead; too high gives a flat, wide bead with spatter. Practise on scrap of the same thickness and inspect the bead profile and penetration.
Candidates apply body filler over bare steel or over paint without sanding and cleaning, or they mix filler with an arbitrary amount of hardener and then sand before it has cured.
They treat filler as paint and skip surface preparation; they also underestimate how hardener ratio and cure time affect adhesion and sandability.
What to do instead
Follow the sequence: bare metal or feathered edge → clean with wax and grease remover → apply epoxy or etch primer where required → mix filler with the correct hardener ratio (by weight or measured strip) → apply in thin coats → allow full cure → sand with the correct grit sequence (e.g. 80, 120, 180) using a sanding block. Check adhesion and pinholes before priming.
Candidates answer colour-matching questions by saying 'use the paint code' and ignore variant colours, spray-out cards, and blending within adjacent panels.
They believe the manufacturer's code guarantees a match, not realising that the same code can have several variants and that weathering changes the appearance.
What to do instead
Learn the colour-matching workflow: obtain the code, check for variant chips or spray-out cards, spray a test card and compare under correct lighting (daylight or colour-corrected lamp), then blend into adjacent panels rather than painting a hard edge at the panel gap. Practise spraying a card and comparing it to the vehicle before mixing a full batch.
Candidates describe structural damage assessment by listing visible bent parts only, without checking reference dimensions, symmetry, or the location of crush zones and high-strength steel components.
They focus on cosmetic damage and do not use body dimensions, diagonal measurements, or manufacturer repair information to decide whether the structure is repairable or must be replaced.
What to do instead
Use a systematic check: measure diagonals and reference points against the manufacturer's body dimensions, inspect for kinks and folds in the rails and aprons, identify high-strength steel and crush zones, and consult the repair manual for sectioning or replacement limits. State that any structural repair must restore the original crash performance and be verified by measurement before refinishing.