Today, greater emphasis is being placed on a component’s ‘machinability’ , but this term is an ambiguous one, having a variety of different meanings, depending upon the production engineer’s requirements. In fact, the machinability expression does not have an authoritative definition, despite the fact that it has been used for decades. In 1938, Ernst in his book on the ‘Physics of Metal Cutting’ , defined machinability in the following manner: ‘As a complex physical property of a metal.