PURPOSE: To improve efficiency of edging work, by folding a curved side edge of each edge unit, integrally formed through a cut groove, while cutting the point end side of said curved side edge so as to be in the same level with a side surface of the edge unit and forming a curved one-edge point in every edge unit.

CONSTITUTION: A sheet of plate-shaped edge unit element material 1, performing press working, integrally forms each edge unit 4 through a cut groove 3. Next the material 1, folding each curved part 2 by press working so as to form an acute angle θ with respect to one side surface 4a of the edge unit 4, continuously forms each curved folding part 5 while provides a round hole 6 penetrating through the edge unit 4. Further the material 1, simultaneously edging the point end side of each curved folding part 5 to be polished and cutting it in a line A so as to be in the same level with the other side surface 4b of the edge unit 4, forms a curved one-edge point 7 in every edge unit 4. The material 1, simultaneously performing this work in the above for each edge unit, provides effectiveness for improving efficiency of the edging work.