PURPOSE: To provide a high accuracy metal mold in the production of a spur gear for automobiles by boring an inner ring blank, forming a specified tooth form in the bore with broaching and then mounting an outer ring on the inner ring.

CONSTITUTION: An inner ring blank made of tool steel softened by spheroidizing annealing or the like is bored to provide a bore zero to 1mm smaller than the root diameter of a spur gear to be produced so that a specified tooth form is formed in the bore by broaching. Thereafter, on the inner ring 1 quenched and annealed is mounted an outer ring 2 made of tool steel or strong steel. Thus, the inner booth form 3 of the spur gear can be broached accurately and further in a short time. A high quality metal mold can be produced with high efficiency and low cost as a whole by the combination of the preceding and succeeding workings.