The machinability of powder metallurgy steels is lower compared with wrought steels of appropriate composition and/or mechanical properties. This is due to a larger number of material and processing variables affecting the final properties of sintered materials. The aim of the book is to present knowledge for an overview of all interacting factors in machining, including those applied for improving machinability. They include the properties of basic plain iron and alloyed powders, various additions, compacting and sintering conditions. The effect of porosity, individual alloying elements and microstructure is considered.