Sanding Grit Progression Guide for Automotive Bodywork & Paint Prep

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Sanding Grit Progression Guide for Automotive Bodywork & Paint Prep

Sanding Grit Progression Guide for Automotive Bodywork & Paint Prep

One of the most common mistakes in auto body work isn't using the wrong product — it's using the right product in the wrong order. Grit progression is everything. Jump too coarse and you risk deep scratches that show through paint. Skip steps and you waste time chasing scratches that should have been removed two grits ago.

This guide walks through the complete grit progression for automotive bodywork and paint prep, from bare metal all the way to final finish, with recommended Indasa disc grits for each stage.

Why Grit Progression Matters

Every abrasive grit leaves scratches in the surface — that's how sanding works. The goal of a grit progression is to use each successive grit to remove the scratches left by the previous, coarser grit, while leaving its own finer scratches for the next step to address. By the time you reach your final grit, the scratches are too fine for paint or primer to telegraph through.

Skipping grits forces a finer abrasive to remove scratches it wasn't designed for, which takes far longer and often produces uneven results.

The Complete Automotive Grit Progression

Stage 1: Bare Metal, Rust Removal & Heavy Material Removal

Recommended grits: 36 – 80

Use coarse grits for stripping old paint, removing rust, grinding welds, or shaping body filler. These grits cut fast and leave deep scratches, so they should only be used where aggressive material removal is needed. Always follow with finer grits — never apply primer over 80-grit scratches.

  • 36–60 grit: Stripping paint, heavy rust, shaping filler
  • 80 grit: Feathering edges, final shaping of filler

Stage 2: Body Filler Finishing & Primer Prep

Recommended grits: 80 – 150

After shaping filler and before applying primer, you need to refine the surface and remove the deep scratches from Stage 1. This is where most of your time is spent on a repair panel.

  • 80 grit: Final filler shaping
  • 120 grit: Smoothing filler, scuffing bare metal for primer adhesion
  • 150 grit: Final surface prep before high-build primer

Tip: Most primers require a minimum of 80-grit surface prep for adhesion, but 120–150 grit gives better results and reduces primer fill requirements.

Stage 3: Primer Sanding

Recommended grits: 180 – 320

Once your high-build primer is cured, sand it to level the surface and remove any texture, runs, or imperfections before topcoat. This is a critical stage — any scratches left here will show through basecoat.

  • 180 grit: Leveling high-build primer, removing heavy texture
  • 220 grit: General primer sanding, feathering edges
  • 320 grit: Final primer sanding before sealer or basecoat

Stage 4: Sealer & Basecoat Prep

Recommended grits: 320 – 400

If you're applying a sealer coat before basecoat, scuff the sealer lightly with 320–400 grit to promote adhesion. On existing painted panels being blended, 400 grit is the standard scuff before basecoat.

  • 320 grit: Scuffing sealer, blending into existing paint
  • 400 grit: Final scuff before basecoat on repaired panels

Stage 5: Clearcoat Prep & Wet Sanding

Recommended grits: 400 – 800+

Wet sanding clearcoat removes orange peel, dust nibs, and runs to achieve a glass-smooth finish before polishing. This stage is typically done by hand or with a dual-action polisher and foam interface pad.

  • 400–600 grit: Removing runs, heavy orange peel
  • 800 grit: Leveling moderate orange peel, prepping for polish
  • 1000–1500 grit: Fine wet sanding before machine polish
  • 2000–3000 grit: Final wet sanding before finishing polish

Quick Reference: Automotive Grit Progression Chart

Stage Task Grit Range
1 Bare metal, rust removal, heavy filler shaping 36 – 80
2 Filler finishing, primer adhesion prep 80 – 150
3 Primer sanding & leveling 180 – 320
4 Sealer & basecoat prep 320 – 400
5 Clearcoat wet sanding & polish prep 400 – 800+

Choosing the Right Indasa Disc for Each Stage

For most automotive bodywork stages, you'll be working with 5" or 6" random orbital discs. Here's how the Indasa lineup maps to each stage:

Hook-and-Loop (Rhynogrip RedLine) — Best for Multi-Grit Workflows

If you're running through a full grit progression on a single sander, hook-and-loop discs let you swap grits in seconds without stopping to peel adhesive liners.

PSA (Rhynostick WhiteLine) — Best for Dedicated Single-Grit Sanders

Many production body shops run dedicated sanders locked to a single grit for each stage. PSA discs are ideal for this workflow — lower cost per disc and a firm, direct bond to the pad.

Pro Tips for Automotive Sanding

  • Never skip more than one grit step. Going from 80 to 220 leaves scratches that 220 can't fully remove in a reasonable time.
  • Use a guide coat. A light mist of contrasting color (or a dry guide coat powder) over primer reveals low spots and scratches you'd otherwise miss.
  • Sand in a cross-hatch pattern. Alternating your sanding direction between passes helps reveal and remove scratches more evenly.
  • Use dust extraction where possible. Vacuum discs (5-hole or 6-hole) dramatically reduce airborne dust and keep the abrasive cutting cleanly, extending disc life.
  • Let primer fully cure before sanding. Sanding uncured primer clogs discs fast and produces poor results. Follow the manufacturer's recoat window.

Related Guides

Shop Automotive Sanding Discs

Questions about which grit or disc to use for your specific job? Contact us — we're happy to help.

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