Студопедия Главная Случайная страница Обратная связь

Разделы: Автомобили Астрономия Биология География Дом и сад Другие языки Другое Информатика История Культура Литература Логика Математика Медицина Металлургия Механика Образование Охрана труда Педагогика Политика Право Психология Религия Риторика Социология Спорт Строительство Технология Туризм Физика Философия Финансы Химия Черчение Экология Экономика Электроника

Read the text and name the most common types of machine-tools.

Types of machine tools commonly used in today’s industries include lathes, drilling and boring machines, milling machines, as well as shapers, planers, and grinding machines.

In a milling machine the cutter 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 accurасу. Angles, slots, gear teeth and cuts can be made by using various shapes of cutters.

To 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 are different in size and function, from portable drills to radial drilling machines, multispindle units, automatic production machines, and deep-hole-drilling machines.

Boring 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.

The shaper 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 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.

Grinders 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.

2. Find the following words and word-combinations in English in the text: стіл (верстата); можливі рухи; обертатися; утворювати точний розмір; гладенька кінцева поверхня; різні за розмірами та функцією; відносно повільний; зворотній хід; важливий/неважливий; встановлювати декілька інструментів одночасно.

3. Translate the following words and word-combinations from the text into Ukrainian: a circular device; a series of cutting edges; hole-making machine-tools; portable drills; radial drilling machines; multispindle units; automatic production machines; deep-hole-drilling machines; a rotating single-point cutter; a boring bar; a stationary workpiece; a slight lateral displacement; straight-line elements; a mass production line; reciprocating machine tools; a fixed workpiece; a rotating abrasive wheel; fine wheel regulation.

Дата добавления: 2015-09-04; просмотров: 1943. Нарушение авторских прав; Мы поможем в написании вашей работы!

Studopedia.info - Студопедия - 2014-2022 год . (0.017 сек.) русская версия | украинская версия