MANUFACTURE OF HEAVY EXPANDING METAL

PURPOSE:To reduce the production cost by executing a hot rolling by coating a release agent on the plural through holes formed on a metal made thick plate and expanding the crashed through hole. CONSTITUTION:Plural through holes 2 are formed in the width direction of a metal made thick plate 1 and a release agent is coated on the inner face. After heating the thick plate 1 upto about 1,200 deg.C, a hot rolling is executed so as to crush an oblong hole 2 with a rolling roller to remove the trimming part 1a of both ends by cutting. The thick plate 1 is then cut in plural sheets by selecting the cutting thickness (t) according to the thickness of the expanding metal of the final product. A hole making cutting tool is pushed into the slit 4 of the thick plate 1n of after cutting to subject each slit 4 to an opening in hexagonal shape. In this way the working of the aperture part can integrally be performed and the work process and amount can be reduced. Consequently the production cost can be reduced.