Abstract: A method is provided for automatically determining the tool path in plane zone machining, consisting in forming cross lining of the zone to be machined with a pitch depending on the diameter of the tool and using this cross lining successively for producing a grid which is the image of the zone to be machined for shifting the zone to be machined and calculating, after the coding of the machinable points of said zone, the path of the axis of the tool in a succession of linear movements directed either parallel to the axes X and Y of the plane or at 45.degree. with respect thereto.