Disclosed is a flange sleeve (10) comprising at least one flange (3) formed thereon, having no gap at the joint or having a controllably adjusted width of the gap at the joint. The flange (13) has two crowding recesses (16, 16null, 16null, 16nullnull) at least in the metal coating thereof in at least two points distributed over the flange in the direction of the periphery. According to the method for producing said flange sleeves (10), the edge of the flange is bent. At least two crowding recesses in at least two points distributed over the flange in the direction of the periphery are made at least in the metal coating thereof, said recesses preferably being made by bending the edge of the sleeve. The invention also relates to a bending tool and a bending device.