| 摘要 |
PURPOSE:To obtain a reel hub having good roundness and a good flatness degree and capable of stably winding up a magnetic tape, by forming a recessed part to the outer peripheral surface of an inner annular part along the peripheral direction thereof by utilizing the molding contraction of a molding material while using the outer peripheral surface of the inner annular part as the one constitutional surface of a cavity during the molding of an outer annular part. CONSTITUTION:An inner annular part 3 is formed into a thin wall at the inner peripheral part thereof surrounding a shaft hole 2 and a thick wall at the outer peripheral part thereof. The molding of this inner annular part 3 is performed under a molding condition easily generating a sink mark such that injection pressure is low or holding pressure is low. When molding is performed under this condition, a recessed part 5 due to the sink mark is formed to the outer peripheral surface of the inner annular part 3 along the peripheral surface thereof and, subsequently, an outer annular part 4 is molded by using the outer peripheral surface of the inner annular part 3 as one constitutional surface of a cavity. The depth of the recessed part 5 is pref. about 0.05-0.2mm. and, when 0.05mm. or less, the outer annular part 4 is easily pulled off from the inner annular part 3 and, when 0.2mm. or more, inferiority such as short is easily generated on the inner annular part 3. |
