Method and apparatus for making single cranks for built-up crankshafts used in large engines

摘要

A method is provided for making single crank throws for built-up crankshafts. The method includes heating an elongated workpiece having a saddle-shaped central area on one surface thereof and forming the workpiece into V-shape by pushing it with a punch into a first-forming die having legs angled between 35 and 65 degrees. The punch is V-shape with opposed surfaces inclined at substantially the same angle as the first-forming die. The workpiece is then reheated and pushed with a punch into a second-forming die having inwardly converging surfaces at an outer portion of the cavity and parallel sidewalls joining the inner end of the outer die surfaces. The apparatus includes a bottom die having a long generally rectangular cavity and top die punch rotatably mounted about a vertical axis on the underside of the press crosshead and a motor drive for rotating the top die punch to alternate positions for forging opposite halves of the workpiece in the lengthwise direction.