Auto Body Filler Sanding: Smooth Repairs Before Painting (80–320 Grit Guide)

When repairing dents or scratches on a car, body filler (like Bondo) needs to be sanded properly before painting. Poor sanding leaves ridges, pinholes, and uneven spots that will show through paint. This guide explains the grit sequence and steps for flawless body filler prep.

Why Sand Body Filler?

Body filler cures hard but not perfectly smooth. Sanding shapes the repair, blends it into surrounding panels, and prepares the surface for primer and paint. Skipping steps leads to wavy or uneven finishes.

Best Tools for Body Filler Sanding

• 9x11 in silicon carbide sandpaper sheets (wet or dry use)
• Sanding block or long board sander
• Dust mask or respirator
• Shop vacuum or tack cloth
• Automotive primer for sealing

Recommended Grit Sequence

• 80 grit: Rough shaping of filler.
• 120 grit: Refine shape and remove coarse scratches.
• 220 grit: Smooth transition into surrounding paint.
• 320 grit: Final finish before primer.

Step-by-Step: Sanding Body Filler

1. Shape with 80 grit. Level high spots and rough out contours. Use 80 Grit (25-pack).
2. Smooth with 120 grit. Refine the repair area for consistency. Stock up on 120 Grit (50-pack).
3. Feather with 220 grit. Blend filler into the factory paint surface. Try 220 Grit (100-pack).
4. Finish with 320 grit. Light sanding prepares the panel for primer adhesion.
5. Vacuum dust. Clean thoroughly before applying primer.
6. Prime. Apply an automotive primer to seal and highlight any low spots.
7. Final check. Sand primer lightly with 400 grit if needed before painting.

Special Cases

For large repairs, use a long board sander to maintain panel straightness. For small dings, a sanding block gives more control.

Pro Tips

• Sand in an X-pattern with coarse grits to keep repairs flat.
• Don’t press too hard—let the paper cut naturally.
• Replace clogged sheets often to avoid scratches.
• Always wear a respirator—body filler dust is harmful.

Aftercare

• Apply primer soon after sanding to prevent filler absorbing moisture.
• Store sandpaper flat and dry for future use.
• Polish paint only after it has fully cured.

FAQs

• Can I skip straight to fine grit? No—filler requires shaping with coarse grits first.
• Do I need to wet sand body filler? No, dry sanding is standard until primer stage.
• What if I see pinholes? Reapply a thin layer of filler or glazing putty, then re-sand.

Watch & Learn

For professional bodywork, shop reliable auto sanding grits in our Metal Sanding Collection.