II. Famous people of science and technology: George Stephenson, Robert Slephenson.

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II. Famous people of science and technology: George Stephenson, Robert Slephenson.

Text A: «MACHINE-TOOIS»

Machine-tools are used toshape metals and other ma­terials. The material to be shaped is called theworkpiece.Most machine-tools are nowelectrically driven. Ma­chine-tools with electrical drive are faster and moreac­curate than hand tools: they were an important element in thedevelopment of mass-production processes, as they allowed individual parts to be made in large numbers so as to beinterchangeable.

All machine-tools havefacilities for holding both the workpiece and the tool, and for accurately controlling the movement of the cutting toolrelative to the workpiece. Most machining operations generate largeamounts of heat, and use coolingfluids (usually a mixture of water and oils) for cooling andlubrication.

Machine-tools usually work materials mechanically but other machining methods have been developed lately. They include chemical machining,spark erosionto machine very hard materials to any shape by means of a continuous high-voltagespark (discharge) between an electrode and a workpiece. Other machining meth­ods includedrilling using ultrasound, and cuttingby means of a laserbeam. Numerical control of machine-tools andflexible manufacturing systems have made it possible for complete systems of machine-tools to be used flexibly for the manufacture of arange of pro­ducts.

Vocabulary:

machine-tools — станки

electrically driven — с электроприводом

shape — форма

workpiece — деталь

accurate — точный

development — развитие

to allow — позволять, разрешать

interchangeable — взаимозаменяе­мый

facility — приспособление

relative —относительный

amount — количество

fluid — жидкость

to lubricate — смазывать

spark erosion — электроискровая об­работка

discharge — разряд

by means of — посредством

beam — луч

drilling — сверление

flexible — гибкий

range — ассортимент, диапазон

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