A device for mowing crop comprising a pair of discs adapted to rotate in the cutting plane, driven with equal angular speeds and pairwise in opposite senses and having each outwardly projecting cutters.A cutter may be bent upwardly due to impact on a stone.In order to avoid further damage of the device the circumferential rim of each disc is incised in between every two cutters essentially along an arc of a circle having a center of curvature located outside the circumferential rim.