What Grit Sandpaper to Use for Auto Body Repair

Auto body repair demands precision, patience, and the right tools—especially sandpaper. Whether you’re smoothing primer, blending paint, or removing rust, choosing the correct sandpaper grit directly affects the quality of your work. Using the wrong grit can cause deep scratches, uneven surfaces, or poor paint adhesion that show up later after you thought the job was done.

Understanding how grit numbers work and when to use each type is essential for achieving a professional finish. In this article, we’ll break down grit ranges, explain their uses at each stage of auto body repair, and offer tips to help you get the best results.

Understanding Sandpaper Grit

Sandpaper grit refers to the number of abrasive particles per square inch of paper. The lower the number, the coarser the grit; conversely, higher numbers mean finer grit.

• Coarse grits (40–80): Aggressive material removal.
• Medium grits (100–220): Smoothing surfaces, feathering edges.
• Fine grits (320–600): Final sanding before paint or clear coat.
• Very fine (800–2000+): Wet sanding and finishing.

In auto body repair, grit choice depends on the task: rough shaping, smoothing filler, preparing for primer, leveling primer, or final finish.

Why Grit Matters in Auto Body Repair

Choosing the right grit impacts:

• Surface contour: Coarse grit can gouge or flatten curves if used incorrectly.
• Scratch pattern: Deeper scratches from coarse grit are harder to remove later.
• Paint adhesion: Primer and paint stick better to surfaces with appropriate scratch patterns.
• Finish quality: Finer grits help deliver smooth, glossy results.

Working in stages—from coarse to fine—is key to professional results.

Stage 1: Removing Old Paint & Rust

Grit Range: 40–80

At the start of auto body repair, you often need to strip paint, remove rust, or take down high spots. This requires aggressive cutting action.

• 40-grit: Extremely aggressive. Good for stripping thick paint layers or heavy rust with a power tool (disc, flap wheel). Not used by hand.
• 60-80 grit: Still coarse but more controllable. Suitable for feathering edges and beginning to blend old paint into bare metal areas.

Tips:

• When using coarse grit with power tools, always keep the tool moving to avoid gouging.
• For hand sanding, 80 grit is more manageable and reduces the risk of deep scratch patterns.

⚠️ Avoid large deep scratches at this stage, because they will show up even after primer and paint if not smoothed properly in subsequent steps.

Stage 2: Shaping Body Filler

Grit Range: 80–120

Once rust and paint are removed and bare metal is exposed, you may need body filler to repair dents or low spots.

• 80 grit: Removes excess filler and shapes contours. Ideal for rough shaping.
• 120 grit: Begins smoothing out the rough body filler to prepare for finer sanding.

Process:

1. Spread filler over low spots and let it cure fully.
2. Start with 80 grit to shape and knock down high spots.
3. Switch to 120 grit to refine curves and make the filler blend into the surrounding surface.

Tips:

• Use a sanding block to maintain flat planes and gentle curves.
• Avoid over-sanding filler at this stage—you want smooth, not shiny. A shiny surface often means you removed too much filler.

Stage 3: Feathering Paint & Primer Edges

Grit Range: 120–220

After body filler shaping, you must feather the transition between old paint and new filler so it’s seamless before applying primer.

• 120 grit: Good for initial feathering.
• 180–220 grit: Smooths edges and prepares surface for primer.

Feathering creates a gradual transition rather than a sharp drop or ridge. This allows primer to lay flat and evenly.

Tips:

• Hand sanding works best for feathering edges so you feel the transition.
• Use long even strokes and check for level with good light.

Stage 4: Sanding Primer and Sealer

Grit Range: 220–400

Primer and sealer hide imperfections and provide a uniform surface for paint. But they need correct surface texture for the next coatings.

• 220–320 grit: Removes sanding scratches from lower grit and smooths primer.
• 400 grit: Often used for final primer prep before base coat.

Process:

1. Apply primer coat(s) and let fully dry/cure.
2. Sand with 320 grit to knock down orange peel and high spots.
3. Finish with 400 grit for a smooth surface before base coat.

Tips:

• Always clean dust off between grit changes.
• Slight pressure is better than heavy sanding to avoid sanding through primer.

Stage 5: Final Paint Preparation

Grit Range: 400–600

Right before painting, you want a surface that’s smooth but still provides a bit of tooth for paint to stick.

• 400–600 grit: Finishes primer without over-polishing. Creates a consistent surface for the base coat.

Professional painters often use wet sanding at this stage with 600 grit:

• Wet sanding reduces dust.
• Water lubricates and prevents deep scratches.
• Scratch patterns are easier to hide under paint.

Tips:

• Use lots of water when wet sanding.
• Spend minimal time at this grit—just enough to smooth small imperfections.

Stage 6: Clear Coat and Polish

After painting, you may need to wet sand and polish the clear coat to remove minor imperfections or orange peel.

Grit Range: 800–2000+

• 800–1000 grit: Removes small defects and orange peel.
• 1200–1500 grit: Smooths surface further.
• 2000 grit and higher: Prepares for polishing compound.

Polishing Steps After Clear Coat:

1. Start with 1000–1200 grit wet sanding only if needed.
2. Progress to 1500–2000 grit.
3. Use rubbing compounds and polishes to bring out gloss.

Important:
Only wet sand clear coat if the paint is fully cured.

Common Sandpaper Types Used in Auto Body Repair

Understanding sandpaper materials helps make the right choice:

• Aluminum Oxide: General-purpose and common for sanding filler, primer, and paint.
• Silicon Carbide: Ideal for wet sanding; sharp and cuts well.
• Ceramic: Very aggressive and durable; good for power tools on heavy material removal.

Power Tools vs. Hand Sanding

Power Tools:

• Grinders and random orbital sanders are excellent for heavy removal (40–120 grit).
• Use backing pads and lower grit discs for shaping.
• Always keep moving to avoid gouges.

Hand Sanding:

• Best for feathering edges, finishing filler, and fine grit sanding (180–400+).
• Provides more control and feels subtle transitions better.
• Use sanding blocks to maintain flat, even surface.

Practical Tips for Best Results

1. Work in Stages

Never skip grits. Jumping from coarse to fine leaves deep scratches that are hard to remove.

Example progression:

• 80 → 120 → 180 → 320 → 400 → 600 → (paint) → 1000–1500 (if needed)

2. Keep Sandpaper Clean

Clogged paper doesn’t cut well and creates uneven surfaces. Clean often or replace paper when it loads.

3. Use Proper Lighting

Shadows reveal low spots, high spots, and flaws. Good lighting helps see what you’re sanding.

4. Test on Scrap

If unsure, practice grit progression on scrap metal or a junk panel.

5. Check Surface Regularly

Wipe down and inspect often. It saves time and prevents over-sanding.

Common Mistakes & How to Avoid Them

Using Too Coarse Grit Too Long

• Can create deep scratches.
• Always move to finer grit as soon as possible.

Skipping Grit Steps

• Skipped grits leave scratch patterns visible after painting.
• Follow logical progression.

Sanding Through Primer

• Especially common with aggressive grit or too much pressure.
• Use light pressure and finer grit for primer.

Poor Dust Control

• Dust interferes with paint adhesion.
• Always clean the surface before painting.

Conclusion

Sanding is both an art and a science. The right sandpaper grit at each stage of auto body repair makes the difference between a DIY job and a professional-looking finish. From removing rust and shaping filler to preparing primer and finishing paint, grit progression matters.

Key takeaways:

• Start with coarse grit (40–80) for heavy removal.
• Use medium grit (80–220) for shaping and feathering.
• Sand primer with 220–400 grit.
• Prepare for paint with 400–600 grit.
• Finish and polish with 800–2000+ grit.

Understanding grit, sanding techniques, and surface preparation techniques ensures smoother panels, better paint adhesion, and quality results that last.