Sandpaper Grit Grading

The grit size (mesh number) of sandpaper directly determines the sanding effect. Low grit (e.g., 40#-100#) has coarse abrasive particles, suitable for removing surface rust, old paint, or quick shaping; medium grit (e.g., 120#-240#) is used for smoothing surfaces and removing scratches; high grit (e.g., 400#-3000#) is used for fine polishing, achieving a mirror-like finish. For example, when repairing automotive exterior paint, low-grit sandpaper is used to sand the old paint first, then gradually transitioning to high-grit sandpaper for polishing, ultimately resulting in a smooth coating.