Answer
Use 60, 80, or 120 grit only for heavy removal. After the rough material is removed, step through 150, 180, and 220 so the coarse scratches do not stay behind.
Why it happens
Heavy removal needs coarse grit, but coarse scratches must be refined before the surface can be finished.
Recommended grit
Use 60 or 80 for aggressive removal, 120 for controlled removal, then refine with 150, 180, and 220.
Wet or dry
Use dry sanding for most heavy removal. Use wet sanding only when the material and work area can handle water.
Success check
The unwanted material is removed and the remaining scratches are ready to be refined by medium grit.
What to do
- Identify whether you are removing paint, rust, rough wood, or old finish.
- Start with 60 grit only for very heavy removal.
- Use 80 or 120 grit when the surface needs controlled cutting instead of aggressive cutting.
- Sand until the unwanted material is mostly removed.
- Move to 150 grit to reduce the coarse scratch pattern.
- Continue with 180 and 220 before moving into fine prep.
- Clean the surface before switching to a finer grit.
Avoid: Do not leave the surface at 60 or 80 grit unless more shaping is still needed. Those scratches are too deep for finish prep.