MACHINE TOOL

any stationary power-driven machine that is used to shape or form parts made of metal or other materials. The shaping is accomplished in four general ways: (1) by cutting excess material in the form of chips from the part; (2) by shearing the material; (3) by squeezing metallic parts to the desired shape; and (4) by applying electricity, ultrasound, or corrosive chemicals to the material. The fourth category covers modern machine tools and processes for machining ultrahard metals not machinable by older methods. Machine tools that form parts by removing metal chips from a workpiece include lathes, shapers and planers, drilling machines, milling machines, grinders, and power saws. The cold forming of metal parts, such as cooking utensils, automobile bodies, and similar items, is done on punch presses, while the hot forming of white-hot blanks into appropriately shaped dies is done on forging presses. Modern machine tools cut or form parts to tolerances of plus or minus one ten-thousandth of an inch (0.0025 millimetre). In special applications, precision lapping machines can produce parts that are within plus or minus two millionths of an inch (0.00005 millimetre). Because of the precise dimensional requirements of the parts and the heavy cutting forces exerted on the cutting tool, machine tools combine weight and rigidity with delicate accuracy. stationary power-driven machine that is used to shape or form parts made of metal or other materials. See tool. Additional reading General works Basic information is provided by Victor E. Repp and Willard J. McCarthy, Machine Tool Technology, 5th ed. (1984); and E. Paul Degarmo, J. Temple Black, and Ronald A. Kohser, Materials and Processes in Manufacturing, 6th ed. (1984). The most authoritative, although highly technical, source for all phases of machine tools is the American Society for Metals, Machining, ed. by Taylor Lyman (1967). A useful history is L.T.C. Rolt, A Short History of Machine Tools (1965). Victor E. Repp, O.A. Ludwig, and Willard J. McCarthy, Metalwork: Technology and Practice, 7th ed. (1982), is a good text for the secondary school level. Comprehensive technical data are given in Eric Oberg, Franklin D. Jones, and Holbrook L. Horton, Machinery's Handbook, 22nd ed. (1984). Electrical methods of machining A.E. De Barr and D.A. Oliver (eds.), Electrochemical Machining (1968), also covers other methods of electrical machining; John F. Wilson, Practice and Theory of Electrochemical Machining (1971), is based on industrial experience, whereas J.A. McGeough, Principles of Electrochemical Machining (1974), deals for the most part with research findings. Detailed discussions on laser and ultrasonic machining can be found in F.T. Arecchi and E.O. Schulz-Dubois (eds.), Laser Handbook, 5 vol. (197285); Morris Cohen (ed.), Materials Science and Engineering: Its Evolution, Practice, and Prospects (1978); see also L.D. Rozenberg (ed.), Physical Principles of Ultrasonic Technology, 2 vol., trans. from the Russian (1973). D.M. Allen, The Principles and Practice of Photochemical Machining and Photoetching (1986), is a useful account of photochemical machining (PCM) and related techniques. Computer-aided machining Serope Kalpakjian, Manufacturing Processes for Engineering Materials (1984); and Geoffrey Boothroyd, Fundamentals of Metal Machining and Machine Tools (1975), are both very informative sources on computer-aided machining as they relate to machine tool technology. For a more technical work, see Raymond Shah, NC Guide: Numerical Control Handbook, 2nd ed. (1979). Two useful introductory texts are Mikell P. Groover and Emory W. Zimmers, Jr., CAD/CAM: Computer-Aided Design and Manufacturing (1984); and David Gibbs, An Introduction to CNC Machining (1984). Willard J. McCarthy Joseph A. McGeough