PURPOSE: To form a cutting blade part hardened by a chill layer in a remelt part which is left by executing a remelt treatment to the part in which a cutting blade of the inside protruded excessively by prescribed dimensions is to be formed, and thereafter, cutting the outside part.

CONSTITUTION: First of all, cast iron is used as a stock, and a trim die A intermediate part which is formed from a block-like base part 2 and a blade base part 3 formed by protruding upward by prescribed height, and in which a projecting part is formed to the outside of a side part furthermore from the blade base part 3 is cast and formed. Subsequently, to the upper face 5 of the edge base part 3, a remelting silimelt processing is performed by prescribed width and depth along a trim line TL by for instance, a TIG welding method using a welding torch, and thereafter, the outside part is cut. Next, its melted zone part is quenched and a satisfactory chill layer of prescribed width and prescribed depth is formed centering around the trim line TL part. Moreover, for instance, by using a two-dimensional numerical control cutter, profile working of the cutting blade face is executed, it is cut to the projecting part of the outside of the trim line TL, and a cutting blade part 10 subjected to chill hardening enough to the extent of a cast steel level is formed in the part of the trim line TL.