Abstract: In a rotary press cutter for the production of envelope blanks, a flexible foil cutting die (8) is used. The leading edge of the foil cutting die (8) is anchored against a leading face (20) of the rotary punching roller (10), and the trailing portion of the foil cutting die (8) extends without creasing over a rounded outer portion of the blade anchorage slot, to be held against the outer periphery of the punching roller (10) by magnetic attraction from inset magnet means (15). The leading edge of the foil cutting die is preformed to provide a location and anchorage flange (24) which is bent without creasing to an obtuse angle to the remainder of the foil, with a radiussed junction between the flange (24) and the remainder of the foil. A unique structure of the magnet means (15) provides very strong adhesion of the body of the foil cutting die (8) to the punching roller (10).