Answer
For cast aluminum, use 180 or 220 for rough texture, then 320, 400, 600, and 800.
Why it happens
Cast surfaces often have texture and oxidation that need medium grit before fine refinement.
Recommended grit
Use 180 or 220 for rough cast texture, then 320, 400, 600, and 800.
Wet or dry
Dry for rough prep; wet for finer stages.
Success check
The cast surface has an even scratch pattern without rough high spots.
What to do
- Clean the cast aluminum.
- Use 180 or 220 on rough texture.
- Refine with 320 and 400.
- Use 600 or 800 before polishing or coating.
Avoid: Do not jump from rough cast texture directly to polishing grits.