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Text С: «MILLING MACHINE»In a milling machine the cutter (фреза) is a circular device with a series of cutting edges on its circumference. The workpiece is held on a table that controls the feed against the cutter. The table has three possible movements: longitudinal, horizontal, and vertical; in some cases it can also rotate. Milling machines are the most versatile of all machine tools. Flat or contoured surfaces may be machined with excellent finish and accuracy. Angles, slots, gear teeth and cuts can be made by using various shapes of cutters. Drilling and Boring MachinesTo drill a hole usually hole-making machine-tools are used. They can drill a hole according to some specification, they can enlarge it, or they can cut threads for a screw or to create an accurate size or a smooth finish of a hole. Drilling machines (сверлильные станки) are different in size and function, from portable drills to radial drilling machines, multispindle units, automatic production machines, and deep-hole-drilling machines. Boring (расточка) is a process that enlarges holes previously drilled, usually with a rotating single-point cutter held on a boring bar and fed against a stationary workpiece. Shapers and PlanersThe shaper (поперечно-строгальный станок) is used mainly to produce different flat surfaces. The tool slides against the stationary workpiece and cuts on one stroke, returns to its starting position, and then cuts on the next stroke after a slight lateral displacement. In general, the shaper can make any surface having straight-line elements. It uses only one cutting-tool and is relatively slow, because the return stroke is idle. That is why the shaper is seldom found on a mass production line. It is, however, valuable for tool production and for workshops where flexibility is important and relative slowness is unimportant. The planer (продольно-строгальный станок) is the largest of the reciprocating machine tools. It differs from the shaper, which moves a tool past a fixed workpiece because the planer moves the workpiece to expose a new section to the tool. Like the shaper, the planer is intended to produce vertical, horizontal, or diagonal cuts. It is also possible to mount several tools at one time in any or all tool holders of a planer to execute multiple simultaneous cuts. GrindersGrinders (шлифовальные станки) remove metal by a rotating abrasive wheel. The wheel is composed of many small grains of abrasive, bonded together, with each grain acting as a miniature cutting tool. The process gives very smooth and accurate finishes. Only a small amount of material is removed at each pass of the wheel, so grinding machines require fine wheel regulation. The pressure of the wheel against the workpiece is usually very light, so that grinding can be carried out on fragile materials that cannot be machined by other conventional devices. Vocabulary: milling machine — фрезерный станок series — серия, ряд cutting edge — режущий край, острие circumference — окружность to feed — подавать longitudinal— продольный horizontal — горизонтальный vertical — вертикальный versatile — универсальный flat — плоский contoured — контурный angle — угол slot — прорезь, паз gear teeth — зубья шестерни drill — дрель, сверло, сверлить hole — отверстие to enlarge — увеличивать thread — резьба portable — портативный unit — единица, целое, узел previously — ранее to slide — скользить stroke — ход lateral — боковой displacement — смещение straight — прямой idle — на холостом ходу workshop — цех, мастерская to mount — крепить holder — держатель to execute — выполнять simultaneous — одновременный multiple — многочисленный grinder — шлифовальный станок wheel — круг, колесо bonded — скрепленный to remove — удалять pass — проход fine — точный conventional — обычный device — устройство, прибор fragile — хрупкий General understanding: 1. What is the shape of a cutter in a milling machine? 2. What moves in a milling machine, a table or a cutter? 3. What possible movements has the table of a milling machine? 4. What kind of surfaces and shapes may be machined by a milling machine? 5. What can we use a drilling machine for? 6. What kinds of drilling machines exist? 7. What is rotated while boring, a cutter or a work-piece? 8. Describe the work of a shaper (planer). 9. What must be done to execute multiple simultaneous cuts on a planer? 10. What is the working tool in a grinder? 11. Can we obtain a very smooth surface after grinding and why? 12. Can we grind fragile materials and why? Exercise 4.3. Translate into English: 1. Токарный станок все еще остается самым важным станком. 2. Все современные токарные станки оборудованы электроприводами. 3. Движение инструмента контролируется с высокой точностью. 4. Электропривод позволяет обрабатывать заготовку на различных скоростях. |