Craftsman Motor Vehicles Body Repair cheat sheet

Personal protective equipment: safety glasses with side shields under a full face shield when grinding; nitrile gloves for solvents and primers; supplied-air or cartridge respirators rated for isocyanates when spraying urethane or basecoat/clearcoat.

Isocyanate (paint hardener) sensitivity is cumulative and can become permanent; spray booths require supplied-air breathing air, not dust masks.

Compressed air for breathing must be Grade D or better; shop air lines must never feed a respirator directly.

Flammable liquids (lacquer thinner, basecoat reducers) must be stored in approved safety cabinets; keep ignition sources and hot-work (welding, grinding sparks) at least 35 ft (11 m) away.

Lockout/tagout applies to booth fans, frame racks, and lift controls before service; never work under a vehicle supported only by a jack.

High-voltage (orange cable) hybrid/EV components: no cutting, welding, or straightening near HV cables until the high-voltage system is de-energized per OEM procedure.

Silicone contamination is the most common cause of paint defects (fish-eyes); keep silicone sprays, tire dressings, and armor-all products out of the prep and paint area.

Dust explosion hazard: aluminum and composite sanding dust must be collected with a bonded/grounded vacuum, never with shop air blow-off.

Body-over-frame: separate ladder frame carries loads; body panels are cosmetic. Unibody: stamped panels and rails form a stressed shell; damage to one area redistributes loads to the whole structure.

Ultra-high-strength steel (UHSS, e.g., 980–1500 MPa) and press-hardened boron steel are not heat-straightenable; OEM procedures usually require sectioning at approved locations or part replacement.

Direct damage is at the impact point; indirect damage appears along load paths (kinks in rails, misaligned door gaps, buckled floor pan, cracked seam sealer).

Collision energy is absorbed by controlled crush zones; measure crush depth and compare to OEM sectioning diagrams before deciding repair vs. replace.

Aluminum body panels require dedicated tools, separate abrasives, and isolation from steel to prevent galvanic corrosion; mixing steel dust into aluminum causes pitting.

Gap and flush measurements (door-to-fender, hood-to-cowl) are the fastest field check for structural shift; record before disassembly for baseline.

Repair vs. replace decision rules: replace if damage is in a crush zone, crosses a body line, or is within an OEM-designated non-repairable zone; repair if in a non-structural, low-strength panel.

Estimate components: parts, labor (body, paint, frame, mechanical), refinish materials, sublet, and betterment/depreciation; each line needs an operation description and time source.

Labor time is expressed in body hours or refinish hours; overlap/split operations must be documented so the same time is not billed twice.

Supplement: any damage found after teardown must be documented with photos and a written supplement before work proceeds; verbal approval is not sufficient.

Work order must record VIN, mileage, keys received, pre-existing damage, customer authorization signature, and payment/insurance details.

Total loss threshold: repair cost plus salvage value compared to actual cash value; state rules vary, so confirm the insurer's formula.

Customer communication: explain repair vs. replace, paint blend within adjacent panels, and that color match is judged under the same lighting; document all approvals in writing.

Diminished value and prior damage disclosure protect both shop and customer; photograph all pre-existing damage at check-in.

Weld removal sequence: locate spot welds (grind to reveal), center-punch, drill or use a spot-weld cutter, then separate with a chisel to avoid panel distortion.

Panel gap tolerance is typically 3–5 mm and must be even front-to-back and top-to-bottom; adjust hinges, shims, and striker before tightening.

Bolted panels (fenders, doors, hoods) align with hinge adjustment; welded panels (quarter panels, roofs) require cutting at factory seams and re-welding at OEM locations.

Hinge adjustment order: set the rear gap first, then front, then up/down; adjust the striker last to match the latch without preload.

Clinch/hem flange on doors and hoods must be sealed with OEM-approved seam sealer after replacement to prevent water intrusion.

Drilling spot welds leaves a plug; replacement panels are attached with plug welds at the same pitch as the original spot welds (typically 25–40 mm).

Panel bonding requires a 10–15 mm bond gap, clean bare metal on one side, and clamp time per adhesive datasheet; do not weld through structural adhesive without OEM approval.

Steel stretches when stretched beyond yield; the goal of straightening is to reverse the stretch by shrinking the high spots, not by adding filler over them.

Heat shrinking: heat a small spot to cherry red (approx. 650–700 °C / 1200–1300 °F), then quench with a damp rag or hammer on-dolly while hot to contract the metal.

Do not heat-shrink UHSS, boron, or aluminum with a torch; aluminum heat-shrink uses a shrinking disc or controlled low heat with a wet sponge.

Hammer-on-dolly planishes and stretches; hammer-off-dolly (dolly behind, hammer striking) raises a low spot and stretches. Off-dolly is for roughing out; on-dolly is for finishing.

Pick and file: use a body file across the repair to reveal high/low spots; file cuts high spots only, so remaining file marks indicate where to shrink.

Stretch occurs from overworked metal (dents worked too long); a stretched panel will oil-can and must be shrunk before filler.

Panel beating sequence: rough out with a bumping hammer, planish with hammer and dolly, then finish with a shrinking disc or file before filler.

Body filler is for cosmetic correction over properly prepared steel; maximum thickness is typically 3 mm (about 1/8 in); deeper areas need metal straightening first.

Surface prep before filler: 80–180 grit scratch, clean with wax and grease remover, and apply to bare metal or epoxy primer per product datasheet.

Polyester filler over cured epoxy primer is acceptable; filler directly over bare steel must be sealed; never apply filler over lacquer, enamel, or unknown coatings.

Plastic repair: identify the substrate (PP/EPDM, TPO, ABS, PC) by the ISO code molded on the back; TPO and PP require a specialty adhesion promoter and flexible filler.

Flexible plastic repair uses a two-part urethane or epoxy adhesive with reinforcing mesh; weld (hot-air) repairs require matching rod material to the substrate.

Composite (SMC/fiberglass) repair: grind a 25 mm (1 in) taper around the damage, laminate with resin and mat/cloth, then finish; do not use polyester filler directly on SMC without epoxy primer.

Mixing ratio errors cause filler to remain soft or shrink; measure by weight with a scale or use the supplied measuring stick, and observe pot life.

GMAW (MIG) is the standard for auto body steel; use 0.023–0.030 in wire and 75/25 argon-CO2 for thin sheet; keep heat input low to avoid warping.

Squeeze-type resistance spot welding (STRSW) is the OEM-preferred method for structural panels; verify with a test coupon and peel test before welding the vehicle.

Plug weld: drill 6–8 mm hole in the replacement panel, clamp tight, weld in a spiral from the center out; do not fill in one pass on thin metal.

Sectioning joints must be placed per OEM procedures; a butt joint with a backing plate or an offset lap joint is used; never section in a crush zone or a designated non-section area.

Aluminum requires AC TIG or push-pull MIG with dedicated wire, a different liner, and a stainless brush; steel tooling contaminates the weld.

Bonding: structural adhesive requires clean, dry, bare metal, a specified bond gap, and full clamp time; adhesive and welding can be combined only where OEM approves.

Cutting: plasma cuts any conductive metal but heat-affected zone must be removed; a reciprocating saw or air saw gives a cooler cut on panels near glass or wiring.

Measure first: a 3D measuring system (or tram gauge/centerline gauge) establishes datum and centerline; record before pulling so you can verify return to OEM dimensions.

Pull direction should reverse the impact direction; pull in small increments and re-measure after each pull to avoid over-pulling and stretching the rails.

Anchor the vehicle at OEM-specified clamping points; clamping at non-designated points can crush rockers or floor pan.

Heat is prohibited on UHSS and boron structural parts; cold straightening only within OEM limits; otherwise replace the section.

Unibody rails can typically be straightened within OEM tolerance; kinked or torn rails, or damage in the crush zone, require sectioning at approved locations.

After structural repair, verify with suspension alignment, door/hood gaps, and a re-measure; document dimensions on the repair order.

Frame rack safety: keep clear of chains under load, use rated chains and clamps, and never stand in line with a loaded chain.

Prep sequence: wash, remove wax/silicone with wax and grease remover (two-rag method), sand, clean again, then prime; never sand contaminated paint.

Grit progression: 80–180 for filler shaping, 320–400 for primer surfacer, 600–800 wet or 500–600 dry for basecoat; finer than 800 can cause adhesion loss.

Epoxy primer seals bare metal and is the required base over aluminum and galvanized steel; apply within the recoat window or scuff before topcoat.

Primer surfacer fills sand scratches; guide coat (aerosol or powder) reveals low spots during block sanding.

Basecoat/clearcoat: apply base to hiding (opaque) at the recommended film build, then clear within the flash window; too much base causes mottling and poor adhesion.

Blending: apply base with a blender or reduced edge into adjacent panels; clear blend within the panel's natural break (body line, edge) to hide the transition.

Film build and booth conditions matter: measure wet/dry film with a gauge; temperature and humidity outside the datasheet range cause solvent pop, blushing, or slow cure.

Urethane-set windshields are structural: the adhesive contributes to roof crush and airbag performance; use only OEM-approved urethane and observe drive-away time.

Glass removal: cut the urethane bead with a cold knife or oscillating blade; protect the pinch weld and repaint any bare metal before reinstalling.

Primer and prep on the pinch weld: apply glass primer to the frit and urethane primer to the pinch weld per the adhesive system's instructions.

Tempered side and rear glass shatters into cubes and cannot be repaired; laminated windshield chips can be resin-repaired if the damage is outside the driver's primary vision area and not in the edge.

Trim clips and fasteners are generally one-time use; replace broken clips rather than gluing trim, and use a plastic trim tool to avoid paint damage.

Airbag and SRS components: disconnect the battery and wait the OEM-specified time before working near airbags; never probe with a test light.

Interior reassembly: verify seat tracks, seatbelts, and airbag connectors are fully latched; a loose connector sets an SRS code and can disable the system.