MANUFACTURE OF DRUM FOR MAGNETIC TAPE

PURPOSE:To eliminate a defect on a desired sliding surface at the time of die-casting, and to easily form a complicated shape by die-casting an aluminum alloy when a drum for a magnetic tape is manufactured, and thereafter, pressure-expanding only a contact part with the magnetic tape with forging. CONSTITUTION:At a fixed drum 1 on the cassette reading magnetic head, a horizontal rib plate 3 is horizontally protruded from a central external surface in the vertical direction of a shaft cylinder 2 having a shaft hole 2a, and upper and lower edge parts are continuously connected to an open external cylinder 4. A thick boss 5 is continuously connected to the base edge part of the shaft cylinder 2 downwardly protruded from the rib plate 3, and a leg 6 fitted at the notch part side edge of the external cylinder 4 is protruded to a little lower position than the lower edge of the external cylinder 4. When the fixed drum 1 is manufactured, the aluminum alloy is die-casted, thereafter, only the contact part with the magnetic tape is pressure-expanded, the defect on the desired tape sliding surface at the time of the die-casting is eliminated, and the complicated shape is easily formed.