Leveling Automotive Body Filler for Paint Prep (80, 120, 220, 400 Grit Guide)

Body filler, often called Bondo, is a staple in auto body repair. It smooths dents and imperfections before painting, but the secret to a flawless finish is sanding through the right grit sequence. If rushed or done incorrectly, you’ll see waves, pinholes, or uneven paint coverage.

Why Sand Body Filler?

Body filler hardens quickly but cures unevenly. Sanding levels the surface, blends the repair with surrounding panels, and preps the area for primer and paint. Without proper sanding, filler lines and defects show through the final paint job.

Tools You’ll Need

• Durable sandpaper sheets
• Sanding block or longboard for flat panels
• Body file (for heavy shaping)
• Masking tape
• Primer and tack cloth

Best Grit Sequence for Body Filler

• 80 grit (25-pack) — For rough shaping and leveling filler.
• 120 grit (25-pack) — Refines surface and removes 80-grit scratches.
• 220 grit (100-pack) — Smooths transitions into surrounding paint.
• 400 grit (50-pack) — Final sanding before primer for a seamless surface.

Step-by-Step: Sanding Body Filler

1. Shape with 80 grit. Use 80 grit sandpaper on a sanding block to shape the filler to panel contours.
2. Smooth with 120 grit. Switch to 120 grit sheets to refine the shape and remove deep scratches.
3. Feather with 220 grit. Use 220 grit sheets to blend filler edges into bare metal or paint.
4. Finish with 400 grit. Apply 400 grit sandpaper for a smooth, primer-ready surface.
5. Clean thoroughly. Wipe with tack cloth before applying primer.

Special Cases

• Large dents: May require multiple filler applications and sanding cycles.
• Curved panels: Use flexible sanding blocks to follow contours.
• Pinholes: Fill with glazing putty and sand again with 220–400 grit.

Pro Tips

• Always sand in long, even strokes to maintain panel shape.
• Use guide coat spray to highlight high and low spots.
• Do not over-sand—thin filler may crack or peel.

Aftercare

• Prime within 24 hours to prevent moisture absorption.
• Sand primer with 600–800 grit before applying color coat.
• Store sandpaper in a dry place for consistent performance.

FAQs

• Can I sand body filler by hand? Yes, but a sanding block keeps surfaces flat.
• What if I see filler lines under primer? Sand again with 220–400 grit until smooth.
• Do I need to wet sand filler? No, dry sanding is preferred before primer.

Watch & Learn

For professional-looking auto body repairs, sanding body filler with the right grits is essential. Stock up on auto body sanding sheets and get your project paint-ready.