NABTEB Vehicle Body Building cheat sheet

Hierarchy of control, most to least effective: elimination, substitution, engineering controls, administrative controls, PPE; PPE is the last line of defence.

Spray painting requires local exhaust ventilation; typical minimum face velocity at an open booth face is 0.5 m/s (about 100 ft/min), and air must not be recirculated unless filtered and monitored.

Isocyanate hardeners in 2K paints cause occupational asthma; sensitisation can follow a single overexposure, so supplied-air respiratory protection and health surveillance apply.

Flash point below 23 °C classes a solvent as highly flammable (GHS Category 2); store in a fire-rated cabinet with bunding and keep ignition sources out.

Welding fume is a carcinogen (IARC Group 1 for welding fumes); extract at the arc, and never weld on containers that held fuel until purged and gas-tested.

Body-shop dust from sanding primer and filler is a respiratory sensitiser and combustible; use wet sanding or dust extraction rated for the material.

Waste segregation rule: solvents, paint sludge, used filters and contaminated rags are hazardous waste; empty dried paint tins may be scrap only where local rules allow.

Eyewash and emergency shower must be reachable within 10 seconds of the battery/acid and chemical mixing areas.

Panel-beating hammer faces: flat face for planishing, crowned face for stretching, cross-peen for shrinking and working into corners.

Dolly types: heel dolly for general panel work, toe dolly for tight flanges, curved dolly matching the panel curvature to avoid marking.

Slapper files and body files cut on the push stroke; use chalk or guide coat to reveal high and low spots before filing.

Body hammers weigh roughly 250–450 g; heavier hammers move more metal per blow and suit rough shaping, lighter ones suit finishing.

A disc grinder for body work uses 115 mm or 125 mm discs; grit sequence for paint removal is typically 40–80, then 120–180 before primer.

Torque wrench calibration should be checked at least annually, and impact wrenches must never be used to tighten torque-critical fasteners.

Compressed-air line pressure for spray guns is set at the gun inlet with the trigger pulled (dynamic pressure), typically 2–3 bar for gravity-feed HVLP.

Workshop housekeeping rule: keep a clear walkway of at least 1 m, and store long sheet metal vertically in a rack to prevent buckling.

Mild steel sheet for body panels: DC01/CR4 typical, tensile strength around 270–350 MPa; high-strength low-alloy steels reach 500–800 MPa and need lower heat input.

Boron steel (press-hardened, ~1500 MPa) must not be heated for straightening; heat destroys the martensitic structure and crash performance.

Aluminium body panels need isolation from steel fasteners to prevent galvanic corrosion; use coated or stainless fasteners and sealant barriers.

Sheet thickness gauge: 1 mm ≈ 20 gauge for mild steel; 0.8 mm ≈ 22 gauge; always confirm with a micrometer rather than assume.

Rivet types: blind pop rivets for non-structural panels, monobolt or structural rivets where shear strength matters; rivet hole diameter matches rivet shank closely.

Threaded fasteners: grade 8.8 means tensile strength 800 MPa and yield 0.8 × 800 = 640 MPa; grade 10.9 gives 1000 MPa and 900 MPa yield.

Adhesive bonding with toughened epoxy or polyurethane complements spot welds; bond-line thickness is controlled by glass beads, typically 0.2–0.5 mm.

Seam sealers must be applied to bare, clean metal; applying over wax or paint causes adhesion failure and water tracking.

Body-on-frame construction uses a separate ladder chassis; the body is isolated by rubber mounts, so panel gaps are less critical than in a monocoque.

Monocoque (unitary) bodies carry load through the sills, floor, A/B/C pillars and roof; a cut sill or pillar removes structural strength and requires sectioned repair.

Crash structure zones: front and rear crumple zones absorb energy, while the passenger safety cell (B-pillar, sills, floor cross-members) must remain rigid.

Common body styles: saloon/sedan with three-box layout, hatchback with a tailgate hinged at the roof, estate/wagon extending the roof to the rear, and MPV with a one-box profile.

Panel gap and flush targets are typically 4–6 mm gap and ±1 mm flush between adjacent panels; check with a gap gauge before final tightening.

Closure adjustment order: set the door to the body aperture first, then adjust the front wing to the door, then the bonnet to the wings.

Bonded windscreens contribute to body stiffness; a cured bead of urethane must reach full strength (typically 24 h) before the vehicle is driven.

Underbody sealant and cavity wax protect against stone-chip and corrosion; apply after all welding and before trim refitting.

Frame straightening pulls must be measured against manufacturer datum points; a 3 mm deviation at a control point can equal 20 mm at the panel edge.

Sectioning a high-strength steel rail is permitted only at the manufacturer's defined cut points, usually away from the crumple zone and reinforcement.

Panel alignment sequence: rear body first, then centre, then front, working from the fixed datum to the adjustable panel.

A frame is checked for diamond, sway, sag, mash and twist; each has a distinct measuring pattern on a dedicated jig or a computerised measuring system.

Flange width for a spot-welded lap joint is typically 12–16 mm; the weld nugget should be at least 4√t mm in diameter for sheet thickness t.

Heat straightening of mild steel panels is limited to dull red (about 600–700 °C); overheating warps the panel and removes work-hardening.

Door skin hemming folds the outer skin over the inner frame; the hem flange should be about 8–10 mm wide with sealant applied in the hem.

Bolted subframes and cross-members use stretch bolts in some designs; these are single-use and must be replaced, not reused.

Bend allowance formula: BA = θ × (π/180) × (R + K × t), where θ is bend angle in degrees, R inside radius, t thickness, K the K-factor (typically 0.33–0.5).

Bend deduction = 2 × outside setback − bend allowance; outside setback = (R + t) × tan(θ/2).

Minimum bend radius for mild steel is about 1 × t; for aluminium alloys it is 1.5–2 × t to avoid cracking.

Neutral axis sits at roughly 0.33 t from the inside face for R/t below 1 and approaches 0.5 t for large radii.

Sheet metal gauge numbering is inverse: higher gauge number means thinner sheet; 20 gauge mild steel is about 0.9–1.0 mm.

Shearing leaves a burr on the underside; deburr before forming, and keep the burr side away from visible faces.

Stretch forming increases surface area and thins the metal; shrinking gathers it and thickens it - never try to shrink a stretched area without annealing.

Cutting lubricant for sheet metal reduces tool wear and edge tearing; clean it off before welding to prevent porosity.

Shrinking methods: heat shrinking with a torch and quench, shrinking hammer on a dolly, or a shrinking disc; all gather metal rather than remove it.

Heat shrinking requires a small cherry-red spot (about 5–10 mm) then rapid cooling with a damp rag to lock in the contraction.

English wheel uses upper and lower anvil wheels; more pressure and closer anvils stretch and crown the panel, while light pressure smooths.

Planishing flattens high spots and work-hardens the surface; it should follow rough shaping, not replace it.

Bead roller forms stiffening beads; bead depth and spacing control panel rigidity more than total metal thickness.

Stretching a panel over a curved form (shot bag or sandbag) uses a mallet with a crowned face; never strike directly over a dolly edge.

Annealing aluminium: heat to about 350–400 °C, then quench or air cool; a soot smear turning white is a field indicator.

Springback after forming is proportional to yield strength and inversely to thickness; over-bend by the calculated springback amount.

MIG welding thin body steel: use 0.6–0.8 mm wire, 75/25 Ar/CO₂ or CO₂, and 30–60 A for 0.8 mm sheet; short-circuit transfer only.

Stitch or skip welding in 20–30 mm runs with cooling between prevents heat distortion on large panels.

Plug (rosette) welds through a punched hole of 6–8 mm replace factory spot welds where access is limited.

Spot weld nugget diameter target is 4√t mm; for 0.8 mm sheet this is about 3.6 mm minimum.

Brazing and bronze welding (MIG brazing with CuSi3) work at about 950–1000 °C, below steel melting point, and suit galvanised or high-strength steel joints.

Oxy-acetylene cutting requires a neutral flame for steel; a carburising flame leaves carbon and a ragged kerf.

Plasma cutting suits thin sheet and stainless; keep the standoff and cut speed constant to avoid dross on the underside.

Never weld galvanised steel without removing the zinc coating at least 10 mm back and using fume extraction; zinc oxide fume causes metal fume fever.

High spot and low spot rule: a high spot is struck directly on the dolly (off-dolly is not used); a low spot is raised by off-dolly hammering around its edge.

Off-dolly technique places the dolly under the low area and hammers the surrounding high metal down onto it, lifting the low spot.

Direct (on-dolly) hammering compresses and stretches the metal between hammer and dolly, flattening a crown.

Use a body file or guide coat to map the panel; file marks show high spots and untouched areas show lows.

Crown must be maintained: flattening a crowned panel without shrinking creates oil-canning, where the panel pops in and out.

Pick and file technique: light pick hammer blows then file to reveal the true shape before filling.

Filler should be applied no thicker than about 3 mm per coat; deeper repairs need metal straightening first.

Always wear hearing protection when panel beating; hammer-on-dolly impacts exceed 100 dB(A) at close range.

Damage classification: minor (cosmetic), moderate (panel and inner structure), severe (frame or safety cell deformation requiring jig measurement).

Pull direction must oppose the impact direction; pulling in the wrong direction folds metal further and work-hardens it.

Measure before, during and after pulling against manufacturer control points; do not pull past the specified dimension and release.

Heat is not permitted on boron and most ultra-high-strength steels; check the manufacturer's repair manual for the specific grade before any heat.

Sectioning joints should be placed away from the maximum stress area, typically 100–150 mm from a bend or reinforcement.

Corrosion protection must be reinstated after repair: zinc-rich primer on bare welds, cavity wax inside closed sections, seam sealer on joints.

Suspension and steering geometry must be rechecked after any structural pull; a 1 mm body shift can alter camber and toe readings.

Repair estimate uses paint times (PT) and body times from a labour guide; refinish time depends on panel area and number of coats.

Surface prep sequence: wash, degrease, strip or sand, feather edges, clean with a tack cloth, then apply primer within the product's recoat window.

Feather edging removes the paint step so the repair blends; sand with progressively finer grit, typically 80 then 180 then 320–400.

Primer types: etch primer on bare steel and aluminium, epoxy primer as a sealer, polyester primer as a high-build filler surfacer.

Paint mixing ratio must be followed by weight or volume as specified; 2K products have a defined pot life, often 4–8 hours at 20 °C.

Spray gun distance is typically 150–200 mm, with 50 % overlap and a 90° gun angle to the surface.

Orange peel comes from too little solvent, too high viscosity, too fast a thinner, or too great a gun distance.

Runs and sags come from too much material per pass, too slow a gun speed, or too close a distance.

Clear coat and base coat flash-off times matter: applying clear before base flashes traps solvent and causes blushing or die-back.

Colour matching uses variant chips and spray-out cards; check under daylight or a colour-corrected lamp, not sodium workshop light.

First-angle projection places the view from the front below the front view; third-angle places it above - check the projection symbol before reading a drawing.

Scale 1:10 means 1 mm on the drawing equals 10 mm on the vehicle; measure the drawing and multiply by the scale denominator.

Tolerance is the total permitted variation between upper and lower limits; a dimension 25 ± 0.5 mm has a tolerance of 1 mm.

Vernier caliper resolution: read the main scale at the zero of the vernier, then add the vernier division that aligns; typical resolution 0.02 mm.

Micrometer reading: main sleeve in 0.5 mm steps plus thimble divisions; a 0-25 mm micrometer with a 50-division thimble reads to 0.01 mm.

Feeler gauge measures gap clearance; combine leaves to match the measured gap and record the total leaf thickness.

Estimating paint quantity: total sprayable area × film thickness ÷ (volume solids × transfer efficiency) gives wet paint volume needed.

Labour time estimate = repair area × standard time per unit area, plus allowance for setup, masking and drying.

COSHH-style assessment must be recorded for every chemical used; the safety data sheet sections 2, 4, 6, 8 and 13 give hazard, first aid, spill, exposure and disposal information.

Noise action values: 80 dB(A) lower exposure action value triggers hearing protection on request; 85 dB(A) upper value makes protection mandatory.

Manual handling rule: keep the load close to the waist, bend the knees, and team-lift panels above about 25 kg.

Solvent vapour is heavier than air; extract at low level as well as at the source to prevent pooling in pits.

Fire extinguisher selection: CO₂ for electrical and solvent fires, foam for flammable liquid pools, never water on live electrical equipment.

Spill response: stop the source, contain with absorbent, prevent entry to drains, and dispose as hazardous waste with a record.

Vehicle lifting: use rated axle stands on firm level ground; never work under a vehicle supported only by a jack.

Air compressor sizing: free air delivery must exceed the combined consumption of the spray gun (often 200–400 L/min) plus any DA sander running at the same time.

Spray gun setup: fluid tip 1.2–1.4 mm for base coat, 1.4–1.8 mm for primer surfacer; too small a tip causes spitting.

DA sander orbit 5 mm suits finishing, 2.5 mm suits finer featheredging; backing pad hardness affects cut rate.

Measuring tools for body work: tram gauge for diagonal comparisons, gap gauge for panel gaps, steel rule and tape for datum checks.

Torque specification is for clean, lightly lubricated threads unless stated dry; reduce torque by about 10–15 % when using anti-seize.

Welder setup: check gas flow at 8–12 L/min at the torch, and replace contact tips when the wire feed stutters.

Tool safety: never use a grinding disc above its marked maximum rpm, and always fit the guard.

Galvanised steel has a zinc coating; welding it produces zinc oxide fume, so remove the coating locally and extract the fume.

Aluminium 5xxx series (e.g. 5754) is common for body panels; it work-hardens and needs annealing before heavy shaping.

Plastics used in bumpers: PP/EPDM and PC/ABS; identify by the ISO marking before choosing a repair method.

Fastener thread pitch: M8 × 1.25 means 8 mm nominal diameter and 1.25 mm pitch; coarse metric pitch for M8 is 1.25 mm.

Structural adhesive cure: full strength typically after 24 h at 20 °C, or accelerated by heat; do not move the vehicle before then.

Spot weld removal: drill with a spot-weld cutter of the same diameter as the nugget, or grind the nugget flat, then separate with a chisel.

Sealers: polyurethane seam sealer for painted joints, butyl for non-painted, silicone only where specified - silicone prevents paint adhesion.

Monocoque load paths: front rails to A-pillar to sill to rear rail; any sectioned member must restore the original gauge and grade.

Body styles: coupe (two doors, fixed roof), convertible (folding or removable roof with reinforced sills), pickup (cab plus separate load bed).

Door construction: outer skin, inner frame, intrusion beam, hinge and latch reinforcement; the beam must never be cut or removed.

Bonnet and boot lids are usually aluminium or steel with hemmed edges; check material with a magnet before repair.

Windscreen bonding uses urethane with a primer system; the bead must be continuous and the glass supported until cured.

Panel gap and flush tolerances are measured with a gap gauge and a straight edge; record before disassembly to restore the same gaps.

Anti-corrosion design includes drainage channels, cavity wax and sealant; blocking a drain hole causes rust from inside out.

Frame types: ladder frame, perimeter frame, and subframe; each has defined crush zones and repair limits.

Control point measurement uses manufacturer dimension charts; compare diagonals - unequal diagonals indicate sway or diamond damage.

Sag is a lowering of the frame centre relative to the ends; mash is a shortening of the frame length.

Diamond damage shows as a parallelogram in plan view; check by measuring diagonals between corresponding cross-member points.

Twist is checked by comparing frame heights at the four corners on a level surface.

Spot weld spacing on a structural panel is typically 25–50 mm; replace with the same count and position, not fewer.

Sectioning joint reinforcement: use a backing plate or insert where the manufacturer specifies, and stagger joints on opposite sides.

Sheet metal thickness conversion: 1 mm ≈ 20 gauge, 0.8 mm ≈ 22 gauge, 1.2 mm ≈ 18 gauge for mild steel.

Bend allowance uses the neutral axis; the K-factor for mild steel at R/t ≈ 1 is about 0.4.

Developed length = flat length of the neutral axis = sum of straight sections plus bend allowances.

Shear cutting force depends on thickness and shear strength; never exceed the rated capacity of the shear.

Hand tools: snips for straight cuts (left, right and straight), aviation snips for curves; keep the cut line visible and the waste side down.

Hole punching leaves a clean hole; drilling needs a centre punch mark and cutting lubricant.

Edge distance for rivets and spot welds is at least 2 × diameter from the sheet edge to prevent tear-out.

Metal moves in three ways: stretching (thinning), shrinking (thickening) and bending (no thickness change at the neutral axis).

Heat shrinking sequence: heat a spot to cherry red, then quench with a damp cloth to contract the metal.

Shrinking disc generates local heat by friction and is faster and more controllable than a torch on thin panels.

English wheel pressure: heavy pressure with small contact area stretches; light pressure with large area smooths.

Planishing hammer has a slightly crowned face; use light overlapping blows with the dolly directly behind.

Beads and swages add stiffness; a bead roller with a 3–6 mm bead is typical for body panels.

Springback compensation: over-form by the amount of springback measured on a test piece of the same material.

MIG welding polarity: wire positive (DCEP) for steel; check the machine before welding aluminium, which may need different settings.

Gas flow rate 8–12 L/min at the torch; too high causes turbulence and porosity, too low gives poor shielding.

Wire stick-out should be about 10–15 mm; too long reduces penetration.

Tack welds first to hold alignment, then stitch in alternating positions to spread heat.

Braze welding uses a bronze filler and a flux; the base metal does not melt, so distortion is lower than fusion welding.

Oxy-acetylene flame types: neutral (equal oxygen and acetylene), oxidising (excess oxygen) and carburising (excess acetylene).

Cutting kerf width depends on tip size and speed; too fast leaves a ragged edge, too slow melts the kerf.

Dolly selection: use a dolly whose curvature matches the panel to avoid creating new low spots.

Hammer-on-dolly compresses metal and flattens a crown; hammer-off-dolly lifts low areas.

Guide coat or chalk reveals the panel shape; file marks show high spots, and untouched areas show low spots.

Oil-canning is a condition where the panel pops between two stable shapes; it indicates lost crown and needs shrinking.

Filler application: mix according to the ratio, apply in thin coats, and sand with a long board to keep the shape.

Panel beating reduces panel thickness; measure before and after with a gauge and replace the panel if it is too thin.

Always support the panel on a suitable body stake or sandbag to absorb impact and prevent distortion.

Assess damage direction and energy path before pulling; the repair plan follows the load path, not just the visible dent.

Pull with a controlled force and re-measure frequently; over-pulling work-hardens the metal and creates new damage.

Heat is restricted on high-strength and boron steels; always check the repair manual for the specific grade.

Sectioning joints should be placed away from maximum stress areas and reinforced as specified.

Reinstate corrosion protection: zinc-rich primer on bare metal, cavity wax in closed sections, seam sealer on joints.

After structural repair, check wheel alignment and suspension geometry, and confirm airbag sensor positions are correct.

Record before and after measurements as part of the repair documentation.

Degrease before sanding; sanding drives contaminants into the surface.

Feather edge the repair area so the paint thickness transitions smoothly; use a guide coat to check.

Primer selection: etch primer for bare steel and aluminium, epoxy for sealing, polyester for high-build filling.

Mixing ratio and pot life must be followed; mixed 2K paint left beyond pot life will not cure properly.

Spray technique: 150–200 mm distance, 50 % overlap, 90° gun angle, and consistent speed.

Defects: orange peel from too little solvent or too much distance; runs from too much material or too close a distance; blushing from moisture in the air line.

Colour match under daylight or a colour-corrected lamp; check variant chips before spraying the panel.

First-angle projection: the view from the front is placed below the front view; third-angle places it above.

Scale 1:10 means 1 mm on the drawing equals 10 mm on the vehicle.

Tolerance is the total permitted variation; a dimension of 25 ± 0.5 mm has a tolerance of 1 mm.

Vernier caliper resolution is typically 0.02 mm; read the main scale at the vernier zero, then add the aligned vernier division.

Micrometer reading: main sleeve in 0.5 mm steps plus thimble divisions; a 50-division thimble reads to 0.01 mm.

Feeler gauge: combine leaves to match the measured gap and record the total thickness.

Paint quantity estimate: sprayable area × film thickness ÷ (volume solids × transfer efficiency) gives wet paint volume.

Risk assessment: identify the hazard, decide who might be harmed and how, evaluate the risk, record the findings, and review.

Exposure limits: workplace exposure limits are given as 8-hour time-weighted averages and 15-minute short-term exposure limits.

Respiratory protection: fit testing is required for tight-fitting masks, and facial hair at the seal prevents a good fit.

Fire safety: keep flammable liquids away from ignition sources, bond and earth containers when decanting, and store in a fire-rated cabinet.

Environmental: prevent spills entering drains, use a bunded store, and dispose of hazardous waste through a licensed carrier.

First aid: know the location of eyewash, emergency shower and first-aid kit, and report all incidents.

Vehicle lifting: use axle stands on firm level ground, never work under a vehicle supported only by a jack.

Compressor free air delivery must exceed the combined consumption of all tools running at once.

Spray gun fluid tip: 1.2–1.4 mm for base coat, 1.4–1.8 mm for primer surfacer.

DA sander orbit: 5 mm for finishing, 2.5 mm for finer featheredging.

Tram gauge measures diagonals to check for body misalignment.

Torque specification assumes clean, lightly lubricated threads unless stated dry; reduce torque when using anti-seize.

Welder setup: gas flow 8–12 L/min, wire stick-out 10–15 mm, replace contact tips when the feed stutters.

Grinding disc speed must not exceed its marked maximum rpm, and the guard must be fitted.

Galvanised steel produces zinc oxide fume when welded; remove the coating locally and extract the fume.

Aluminium 5xxx series is common for body panels; it work-hardens and needs annealing before heavy shaping.

Bumper plastics: PP/EPDM and PC/ABS; identify by the ISO marking before choosing a repair method.

M8 × 1.25 means 8 mm nominal diameter and 1.25 mm pitch.

Structural adhesive reaches full strength after about 24 h at 20 °C; do not move the vehicle before then.

Spot weld removal: drill with a spot-weld cutter or grind the nugget flat, then separate with a chisel.

Silicone sealant prevents paint adhesion; use only where specified.

Monocoque load paths run from the front rails to the A-pillar to the sill to the rear rail.

Body styles: coupe, convertible, pickup, saloon, hatchback and estate.

Door intrusion beams must never be cut or removed.

Bonnet and boot lids may be aluminium or steel; check with a magnet before repair.

Windscreen bonding uses urethane with a primer system and a continuous bead.

Record panel gaps and flush before disassembly to restore the same gaps.

Blocking a drain hole causes rust from inside out.

Frame types: ladder, perimeter and subframe; each has defined crush zones and repair limits.

Unequal diagonals between corresponding points indicate sway or diamond damage.

Sag is a lowering of the frame centre; mash is a shortening of the frame length.

Twist is checked by comparing frame heights at the four corners on a level surface.

Spot weld spacing on structural panels is typically 25–50 mm.

Use a backing plate or insert where the manufacturer specifies, and stagger joints on opposite sides.

Control point measurements are compared against the manufacturer's dimension chart.

1 mm ≈ 20 gauge, 0.8 mm ≈ 22 gauge, 1.2 mm ≈ 18 gauge for mild steel.

Bend allowance uses the neutral axis; K-factor for mild steel at R/t ≈ 1 is about 0.4.

Developed length = sum of straight sections plus bend allowances.

Never exceed the rated capacity of a shear.

Aviation snips: left, right and straight cuts; keep the cut line visible.

Drilling needs a centre punch mark and cutting lubricant.

Edge distance for rivets and spot welds is at least 2 × diameter.

Metal moves by stretching (thinning), shrinking (thickening) and bending (no thickness change at the neutral axis).

Heat shrinking: heat a spot to cherry red, then quench with a damp cloth to contract the metal.

A shrinking disc generates local heat by friction and is controllable on thin panels.

English wheel: heavy pressure with small contact area stretches; light pressure with large area smooths.

Planishing hammer has a slightly crowned face; use light overlapping blows with the dolly behind.

Beads and swages add stiffness; a 3–6 mm bead is typical for body panels.

Over-form by the measured springback on a test piece.

MIG welding polarity: wire positive (DCEP) for steel; check the machine for aluminium.

Gas flow 8–12 L/min at the torch; too high causes turbulence and porosity.

Wire stick-out about 10–15 mm; too long reduces penetration.

Tack welds hold alignment; then stitch in alternating positions to spread heat.

Braze welding uses a bronze filler and flux; the base metal does not melt, so distortion is lower.

Oxy-acetylene flame types: neutral, oxidising and carburising.

Cutting kerf: too fast leaves a ragged edge, too slow melts the kerf.

Use a dolly whose curvature matches the panel to avoid creating new low spots.

Hammer-on-dolly compresses metal and flattens a crown; hammer-off-dolly lifts low areas.

Guide coat or chalk reveals the panel shape; file marks show high spots.

Oil-canning indicates lost crown and needs shrinking.

Mix filler according to the ratio, apply in thin coats, and sand with a long board.

Panel beating reduces thickness; measure before and after and replace if too thin.

Support the panel on a body stake or sandbag to absorb impact.

Assess damage direction and energy path before pulling; the repair plan follows the load path.

Pull with controlled force and re-measure frequently; over-pulling work-hardens the metal.

Heat is restricted on high-strength and boron steels; check the repair manual.

Sectioning joints should be away from maximum stress areas and reinforced as specified.

Reinstate corrosion protection: zinc-rich primer, cavity wax and seam sealer.

After structural repair, check wheel alignment and airbag sensor positions.

Record before and after measurements as part of the repair documentation.

Degrease before sanding; sanding drives contaminants into the surface.

Feather edge the repair area and use a guide coat to check the transition.

Etch primer for bare steel and aluminium, epoxy for sealing, polyester for high-build filling.

Follow the mixing ratio and pot life; mixed 2K paint left beyond pot life will not cure properly.

Spray technique: 150–200 mm distance, 50 % overlap, 90° gun angle, consistent speed.

Orange peel from too little solvent or too much distance; runs from too much material or too close a distance.

Colour match under daylight or a colour-corrected lamp before spraying the panel.

First-angle projection places the front view below the front view; third-angle places it above.

Scale 1:10 means 1 mm on the drawing equals 10 mm on the vehicle.

Tolerance is the total permitted variation; 25 ± 0.5 mm has a tolerance of 1 mm.

Vernier caliper resolution is typically 0.02 mm.

Micrometer reading: main sleeve in 0.5 mm steps plus thimble divisions; 50 divisions read to 0.01 mm.

Feeler gauge: combine leaves to match the gap and record the total thickness.

Paint quantity estimate: sprayable area × film thickness ÷ (volume solids × transfer efficiency).