Precipitation hardening (PH) stainless steels develop very high strength by adding elements such as Copper, Niobium and Aluminum to the steel. During heat treatment, very fine particles form in the matrix of the steel imparting additional strength. These stainless steels, types 13-8, 15-5, 15-7, 17-4 and 17-7 can be machined to quite intricate shapes and close tolerances before the final heat treating as there is minimal distortion occurring.