Sinter-hardened and heat-treated PM materials are considered as the most difficult materials to be machined due to their martensitic structure and high hardness. Machining these types of materials is usually low productivity and/or short tool life. A new machining enhancement additive has been developed aiming to improve the machinability of sinter-hardened and heat-treated PM materials. The performance of the newly developed machinability enhancing additive has been evaluated through designated machinability tests with 6 different sinter-hardened and heat-treated materials that were prepared and tested in actual production conditions. It has been demonstrated as an effective machinability additive for sinter hardenable materials with enabling productive machining and/or extending tool life.