Have the parts in a proper heat treatment oven with accurate,stable temperature control.Also make sure there is a proper airflow around the part.Rapid quenching is the key,most have a dunk tank directly underneath the oven to get the heat away quickly to set the hardness.After quenching you have about 20sec for the part to be fully hard as there will be some distortion involved.Best thing is to take the forming jig that made the part and clamp it back into it straight after quenching.