Patent ID: 7077993

Claim:
Apparatus for reducing cracking at the body-shank junctions of a hardened steel die block, by softening the shank portion only, the shank portion of said die block having a flat surface, said apparatus including, in combination support structure for maintaining a die block having a body portion and a shank portion stationary during processing, an electric heat source in close proximity to the flat surface of the shank portion of the die block, said flat surface being uncovered, said electric heat source being composed of parallel runs of heating elements, all portions of adjacent parallel runs of said heating elements being substantially equally distantly spaced from one another in a common flat plane, all portions of said adjacent parallel runs of said heating elements being substantially equidistantly spaced from the entire flat surface area of the shank portion of the die block which is in close heat transference proximity thereto, said electric heat source being positioned to impinge heat from t he electric heat source uninterruptedly directly on to the uncovered flat surface of the shank portion of the die blocks, control means which limit the amount of heat energy which impinges onto the uncovered flat surface of the shank portion to an amount which softens only the shank portion of the die block to a hardness level lower than the hardness level of the body portion of the die block which is underneath and integral with the shank portion to effect differential hardening between the shank and body portions of the die block whereby subsequent cracking at the shank-body junction of the steel die block is substantially eliminated, and structural heat blocking members surrounding the electric heat source at all locations except where the flat surface shank portion of the die block is located in unobstructed facing relationship to the heating elements of the heat source.