In recent years a considerable volume of research has been carried out to improve the techniques employed in the most widely used metal machining processes. An essential preliminary to all these experiments in turning, milling, drilling, tapping, etc., was accurate control of tool shapes. This necessitated the development of adequate tool-measuring equipment and a comprehensive nomenclature. The nomenclature has resulted from an analysis of tool geometry, and an examination of applicable tool grinding methods and inspection equipment. The nomenclature has been extended to take account of factors which were proved by research to be of considerable practical significance in the ultimate tool performance. Nomenclatures for the most commonly used types of tool are presented as a basis for discussion together with typical examples of tool geometry, tool grinding methods, and tool inspection equipment which should be taken into account when developing improved nomenclatures. Reference is also made to some of the British, European, and American standards, which have an important place in these discussions. Some of the problems involved in the workshop application of cutting tool nomenclatures are also considered. Recently, significant advances have been made in tool nomenclature as a result of the increasing co-operation between manufacturers and users of tools, but the nomenclature used for development work in research stations, colleges, universities, and industrial research laboratories, needs to be more comprehensive and precise than that at present used in general engineering practice.