The Concept of Machinability

At first sight, the definition of the term ‘machinability’ presents little difficulty. It is the property of a material which governs the ease or difficulty with which a material can be machined using a cutting tool. The term is in wide use by those concerned with engineering manufacture and production, yet detailed enquiries would reveal a measure of vagueness about its precise definition, or even its general meaning. Unlike most material properties, there is no generally accepted parameter used for its measurement and it is evident that, in practice, the meaning attributed to the term ‘machinability’ tends to reflect the immediate interests of the user. The engineer concerned especially with surface finish problems tends to think in terms of ‘finishability’, others may consider that the term can be used legitimately to indicate the consistency with which a material behaves in a particular machine tool set-up under a constant set of machining conditions, whilst some may consider it to be a measure of the useful life of the cutting tool. In most fields of science and technology great care is devoted to the definition of relevant parameters, but, in machining, machinability tends to remain a term which means ‘all things to all men’.