Abstract: The invention relates to a method for machining and forming transcurrent openings in fibre-reinforced composite materials. Openings with damage-free edges can be formed with high precision by positioning a rotating grinding tool in a preformed hole. In conjunction with this the material is arranged in such a way that the axis of rotation of the grinding tool is essentially perpendicular to the longitudinal direction of the fibres at the edge of the hole. The opening is machined and formed by causing the grinding tool on the one hand to rotate about its own axis and on the other hand to describe an orbital motion relative to the edge of the hole. Any damage/defects caused in the course of preforming are removed in this way.