Complete Sandpaper Grit Guide for Collision Repair (40–3000+)

Why Grit Selection Makes or Breaks Your Repair

A scratch from the wrong grit can cost you two hours of rework. Jump too many grits and your clear coat lays over sand scratches that show up a week later when the customer parks in sunlight. Skip a step and your feather edge telegraphs through primer.

This guide walks through every grit range used in a typical collision repair — from bare metal prep to final buff — with specific product recommendations, disc types, and the machines that run them.

The Coarse Range: 36–80 Grit

36–40 Grit — Heavy Stripping

This is your demolition grit. Use 36–40 grit exclusively for removing heavy mill scale, thick undercoating, seam sealer, or multiple layers of old paint down to bare metal. Run it on a DA (dual-action sander) with a rigid backing pad or a right-angle grinder.

3M Cubitron II 36+ on a grinding disc removes material faster than conventional aluminum oxide because the precision-shaped grain fractures to stay sharp. Norton Blaze Rapid Strip discs also work well here without loading up on soft substrates like fiberglass.

Warning: Never take 36 grit directly to sheet metal on a quarter panel — you'll thin the substrate and create heat warping. Reserve it for structural areas or multi-layer strip jobs.

60–80 Grit — Shaping and Rough Sanding

After heavy stripping, 80 grit is your go-to for shaping body filler and knocking down high spots. On a rigid DA like a Dynabrade or 3M Clean Sanding system, 80 grit removes filler quickly without gouging into the surrounding substrate.

Sunmight Gold 80-grit hook-and-loop discs provide a good balance of cut rate and disc life for filler work. For large flat panels, use 80-grit on a long board — Mirka Abranet 80 grit on a Mirka hand block gives consistent flat results across door skins and fender crowns.

The Medium Range: 100–220 Grit

100–120 Grit — Filler Finishing and Feathering

Once your filler is shaped with 80, step to 120 grit to refine the surface and begin feathering paint edges. A 120-grit disc on a 6-inch DA removes the 80-grit scratches while still cutting fast enough to level filler ridges.

This is also where you feather-edge existing paint layers. The goal is a smooth taper — each paint layer graduating outward — with no hard edges. Work the feather edge 3–4 inches beyond the repair area. 3M 255P Gold 120-grit or Sunmight Gold 120-grit discs handle this well.

150 Grit — Transition Grit

150 grit is a bridge step. In a high-production shop running waterborne basecoat, some painters jump from 120 to 180 and skip 150 entirely. But if you're working with solvent-based single-stage or metallic colors that show scratch patterns easily, running 150 between 120 and 180 eliminates risk.

180 Grit — Primer-Ready Surface

180 grit is the standard scratch pattern for 2K primer-surfacer adhesion. Most epoxy and urethane primer-surfacers are formulated to fill and adhere to a 180-grit scratch. Sand the entire repair area, including the feather edge and 6+ inches of surrounding OEM paint, with 180 before priming.

Mirka Gold 180-grit on a 6-inch DA or Sunmight Gold 180 hook-and-loop discs are shop staples for this step.

220 Grit — Final Bare-Metal and Primer Prep

220 grit is the finest you should go on bare metal before epoxy primer. Any finer and you risk adhesion problems — epoxy needs mechanical tooth. On existing OEM finishes that you're scuffing for blending, 220 is the starting point before sealer.

The Fine Range: 320–600 Grit

320 Grit — Primer Block Sanding (First Cut)

After your 2K primer-surfacer cures, 320 grit is your first block-sanding pass. This levels the primer surface and removes orange peel, nibs, and high spots. Use 320-grit on a long board for flat panels and a flexible hand pad for crowns and body lines.

3M Hookit Purple 320 or Norton Multi-Air 320 on a Cyclonic DA works efficiently here. If you're hand-blocking, Sunmight Film 320 on a Dura-Block provides excellent feedback through the block.

400 Grit — Primer Block Sanding (Final Cut)

400 grit is where most shops finish their primer block sanding before sealer and basecoat. A 400-grit scratch pattern is fine enough for most basecoat systems to cover without sand-scratch show-through. Run 400-grit on your entire primed area plus 2–3 inches into the blend zone.

For waterborne systems, some OEM specs call for 400 dry as the final primer sand. For solvent basecoats, you can typically go 400 dry or 500 wet.

500–600 Grit — Scuff and Blend Prep

500 and 600 grit are your blend-panel and scuff grits. When you're blending basecoat onto an adjacent panel, scuff the entire panel with 500–600 grit (or a gray scuff pad equivalent) so your clear coat adheres to the OEM finish.

Kovax Super Assilex 500-grit sheets are ideal for this — the flexible foam-backed film conforms to contours without cutting through edges. Mirka Abralon 600 pads also work well on curved surfaces like bumper covers.

The Ultra-Fine Range: 800–3000+ Grit

800–1000 Grit — Wet Sanding Clear Coat (Nib Removal)

After clear coat cures, 800–1000 grit wet is your starting point for removing runs, nibs, and heavy orange peel. Soak your paper for at least 10 minutes before use. Keep the surface flooded and use a hard rubber backing block for flat areas.

Kovax Assilex Super Tack 800 or 3M Wetordry 1000-grit sheets are standard here. Use 1000 grit as a starting point for moderate orange peel; drop to 800 only for significant texture or runs.

1200–1500 Grit — Wet Sanding (Leveling)

After knocking down texture with 1000, step to 1200 or 1500 to refine the scratch pattern before compounding. 1500-grit is the most common final wet-sand grit before machine compounding — it produces a haze that a quality compound removes in one or two passes.

Sunmight Film 1500 wet/dry or 3M Wetordry 1500 are reliable choices. For speed, Kovax Super Assilex Orange (1500 equivalent) on a DA eliminates hand-sanding time.

2000–3000 Grit — Final Wet Sand Before Polish

2000–3000 grit is for painters who want a faster, easier compound step. Running 2000 after 1500 reduces the work your compound has to do, which means less heat, less risk of burn-through, and a higher final gloss. Some shops skip 2000 entirely and go straight from 1500 to compound — the tradeoff is more compounding time and more pad wear.

3M Trizact 3000-grit discs on a DA produce an extremely uniform scratch pattern that compounds out quickly, making them popular in high-volume shops running 15+ paint jobs per week.

Quick-Reference Grit Chart

Matching Abrasive Type to the Job

Aluminum Oxide vs. Ceramic vs. Film

Standard aluminum oxide discs (like the classic gold discs) are cheap and work fine for primer sanding and light filler work. Ceramic abrasives — 3M Cubitron II, Norton Blaze — cut faster, last longer, and stay sharper under heat, making them the better choice for filler shaping and heavy sanding.

Film-backed abrasives (Sunmight Film, Kovax Assilex, Mirka Abralon) give a more uniform scratch pattern than paper-backed sheets. For any sanding step that directly affects final paint quality — 400+ grit primer sanding, blend scuffing, wet sanding — film abrasives reduce the risk of rogue deep scratches.

Hook-and-Loop vs. PSA

Hook-and-loop (Velcro-style) discs swap fast, which matters when you're burning through discs on filler. PSA (pressure-sensitive adhesive) discs sit flatter on the pad and cost less per disc. High-volume shops tend to run PSA for primer sanding and hook-and-loop for everything else.

Common Grit Mistakes

Skipping grits: Jumping from 80 to 180 leaves deep 80-grit scratches that primer fills unevenly. The primer looks flat, but the scratches telegraph through basecoat within weeks. Always step through grits — never skip more than one grade.

Going too fine before primer: Sanding bare metal to 400 grit before epoxy primer reduces adhesion. Epoxy needs a 180-grit scratch minimum. Finer surfaces create a smoother profile that the primer can't grip.

Wet sanding too aggressively: Starting at 800 grit on a standard clear coat (2.0–3.0 mils thick) with heavy pressure risks cutting through to basecoat. Start at 1500 unless you're removing a specific defect. Check film thickness with a mil gauge before you begin.