An apparatus for forming by casting or molding a gifted article internally threaded hole of a

摘要

A method of casting or moulding an article having an internally screw-threaded hole comprises introducing casting or moulding material into a mould cavity around a core pin formed with segments of a screw thread separated by flutes and also around withdrawable flat core members projecting into the mould cavity with their leading ends fitting snugly into the flutes. The segments of screw thread form the male image of segments of the required female thread. When the casting or moulding material has set first the core members are withdrawn from the mould cavity then the core pin is rotated to bring the screw-threaded segments into the positions formerly occupied by the flutes and the pin is withdrawn axially from the mould cavity. Finally the article is removed from the mould cavity.