To provide a punching die for cutting a synthetic resin material of hard nature, a punching method for synthetic resin material of hard nature, and a plate material for molding a rotational symmetrical piece, and offer a method of manufacturing plates.
A punching die is structured so that cutters 11 and 12 in the form of oblong circle are fitted by pressure to an upper 3 and a lower base board 4 made of wood and arranged opposing as protruding 1-10 mm from the boards. When a synthetic resin plate 20 of hard nature is to be punched off, the maximum amount of sideways dislocation of the opposing tips of cutters 11 and 12 is made 0.02-0.3 mm while the drive-in depth of the tips is made 0.05-0.4 mm. A plate material for molding a rotational symmetrical piece made of synthetic resin of hard nature has a thickness of 0.2-6 mm and a shape of oblong circle and is formed using the above-mentioned die.
TEIKOKU PISTON RING CO LTD
SHINEI SHOJI KK
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