If you want the grilles to have a brushed or polished look or both, the next step is wet sanding.
For a polished finish, start with 220-grit sandpaper, move to 600 and then finish with 1,500. The next step is polishing the aluminum. Using a soft-cotton buffing wheel 6 inches or larger, bring the aluminum up to a brilliant shine.
After the polishing is complete (in this case I only polished the outer edge of the grille bars), a brushed finish can be added to the grille rings and the sides of the grille bars. To do this, simply glue a large piece of 220-grit sandpaper to a flat surface like a bench top and lay the aluminum on the sandpaper pushing it in one direction only. A fence guide can be used to keep your lines straight. These photos show what the finished work looks like. Tip: For the smaller grille bars, such as those for the tweeters, make square rings. After polishing and brushing, simply cut the squares apart and discard the center sections This will keep your fingers out of harm's way when routing small parts.
To save on material, trace the smaller pieces inside of the larger ones.
Next, mark and attach the larger grille bars using metal epoxy and screws. Use thread lock on the screws to make sure they won't work their way out. For the smaller tweeter grilles, epoxy alone works fine. Tip: To remove excess epoxy, wait until the epoxy is firm enough to cut but not fully hardened. Carefully trim away the excess with an X-acto knife.