How to Sand Automotive Body Filler for a Smooth Finish (80, 120, 220, 320 Grit Guide)

When repairing dents and scratches on vehicles, body filler (Bondo) is a go-to solution. But even a perfect application looks uneven without proper sanding. Each grit plays a role in shaping, smoothing, and blending the repair into surrounding panels. This guide explains how to sand body filler step by step using 80, 120, 220, and 320 grit sandpaper.

Why Sanding Body Filler Matters

Body filler cures hard and must be leveled before painting. Sanding shapes the filler, feathers edges into bare metal, and creates the right surface profile for primer and paint. Skipping or rushing sanding can leave waves, pinholes, or visible seams.

Tools You’ll Need

• 80–320 grit sandpaper – coarse to medium-fine for automotive repair.
• Sanding block or longboard – ensures flat, even sanding.
• DA sander (dual-action) – speeds up work on large areas.
• Guide coat – highlights high and low spots.
• Respirator & goggles – body filler dust can be harmful.

Best Grit Sequence for Body Filler

• 80 grit: Rough shapes filler immediately after curing.
• 120 grit: Smooths surface and feathers edges into surrounding metal.
• 220 grit: Refines scratches and prepares for primer.
• 320 grit: Final step for a paint-ready surface.

Step-by-Step Body Filler Sanding

1. Start with 80 grit. Rough shape filler and remove excess using 80 grit (50-pack).
2. Move to 120 grit. Feather edges into bare metal with 120 grit (25-pack).
3. Refine with 220 grit. Level the repair area for primer using 220 grit (100-pack).
4. Finish with 320 grit. Smooth the surface for paint application using 320 grit (25-pack).
5. Check with guide coat. Apply a light mist of contrasting paint, sand again to reveal any low spots.

Special Cases

For deep dents, apply body filler in thin layers, sanding each one before adding the next. For small cosmetic repairs, you can start at 120 grit and skip 80 grit. Always finish at 320 grit before primer for best adhesion.

Pro Tips

• Sand in long, even strokes to avoid creating waves.
• Use cross-hatch sanding patterns to maintain flatness.
• Always use a sanding block for precision.
• Replace paper often—body filler clogs sandpaper quickly.

Aftercare

• Prime immediately after sanding to prevent moisture absorption.
• Inspect under bright light before painting—imperfections become obvious under glossy finishes.
• Polish and seal the final paint job to protect repairs.

FAQs

• Can I paint directly over body filler? No—always prime first.
• Do I need to wet sand filler? No—always dry sand to avoid clogging and softening.
• Is 320 grit smooth enough for paint? Yes—320 grit provides the ideal profile for primer and paint adhesion.

Watch & Learn

For reliable auto bodywork, explore our metal sanding collection.