Sometimes it’s hard to sand a flat surface without curving certain areas.
A simples solution is to reverse the way we usually work.
Instead of holding the piece steady and passing the sandpaper over the surface, try placing the sandpaper o the table and passing the metal over it in a circular fashion until you get a perfect finish.
I will use a ring as an example.
1. With a permanent marker we paint the area we wish to sand.
2. We place a sheet of sandpaper on the table or other flat area. The sandpaper can be taped to the table.
3. We move the metal over the sandpaper in a continuous figure 8 movement to make sure that we apply even pressure to the whole area.
4. The ink disappeared in the area that came into contact with the sandpaper. There is still a small black area that was lower and therefore didn’t touch the sandpaper. A little more sanding is required to even it out. I repeated the process until the surface of the metal was clean.
5. The process can be repeated with all the grades of sandpaper you normally go through before moving on to the polishing stage.