The free cutting steels is part of engineering steels courses. The engineering steels is part of the steel applications set of courses. In this course, the definition of machinability and the factors that affects machinability will be developed. After that, the MnS inclusions, the re-shulphurised steel to improve strength will be studied. Then, the effect produced by a notch in medium free cutting steels will be analysed. Next, different chemical additions like lead, bismuth, tellurium and selenium will be analysed. Finally, the additions affecting machinability and the cost will be evaluated.