Hex dies repair damaged, worn, or rusted threads on the outer surfaces of parts so they can be mated with holes or other parts that have matching internal threads. Each die can repair one size of threads. A cylindrical part such as a rod is inserted into the opening on the die, and the die is rotated around the part to restore the external threads on the part. The dies' hexagonal shape allows them to be turned with a standard wrench or a compatible die wrench.