Abstract
In die casting mold and plastic mold，the cooling holes are designed for increasing cooling efficiency by cooling water． Recently, as purpose of high cycle of molding，the position of cooling holes has been closer to the mold surface，and the number of cooling holes has been increasing．If cooling and heating are repeated in mold，stress corrosion cracking and fatigue corrosion cracking are likely to occur at the cooling hole wall, then this phenomenon might be cause of short mold life．In order to solve this problem，mold manufacturer designs sphere radius(SR) at the hole bottom to avoid thermal stress. Therefore, we developed drill for SR machining，and we researched cutting method for SR machining for improving mold life．As a result，the cutting method of " Finishing the hole wall and hole bottom SR " can eliminate the slight step difference between them．The cutting method improve the surface roughness of the hole wall，and improve the mold life.
