Flat Washers from Steel Sheet

A plain washer spreads a nut's or bolt head's load and protects the surface under it. ISO 7089 gives the M6 washer as 6.4 mm bore, 12 mm outside and 1.6 mm thick. Drill the bore first while the sheet is still large and easy to hold, cut the washer out roughly, then spin it on a bolt in a drill and file it round.