You can refer to metal bits that fall or chip off as “swarf” or chıppings, flakes, shards. If they are sharp and pointed like broken glass “shards” is the best answer. İf they look like the curly bits that come off a lathe “swarf” is the correct word. Chips = little bits lıke tiny stones. Flakes if they look like thın slices of curly cheese from a grater.