a method and apparatus for bevelling interior angles of sheets of coloured or non - coloured plain glass , plate glass or flattened glass , is disclosed . the vertex of the interior angles is bevelled , with assigned rake and bevel angles of the rotary tool , by moving the tool parallel to the bisector of said angle , first on one side and then on the other side of the bisector , with the active part of the tool substantially tangential to the bisector . the apparatus comprises at least one rotary tool such as a grinding wheel , drive means for rotating the tool , a first member for supporting the tool and a rotary assembly or the like to enable them to be moved angularly within a first vertical plane about a diameter of the tool . a second member supports the first member in such a manner as to enable them to be moved angularly within a second vertical plane perpendicular to the first vertical plane . the second member is supported in such a manner as to enable the tool to be moved in three mutually perpendicular directions and rotated about one of the directions . a sheet of coloured or non - coloured plain glass , plate glass or flattened glass with at least one bevelled interior angle is produced .