Text 1a

The technological advances in the field of machining during the past 100 years have made this manufacturing process a very important and essential one. It may be said that the machine tool is to our mechanized era what power was to the industrial revolution. In fact without our machine tools the engines that provide our industrial and domestic power would be nonexistent.

Machining is the manufacturing process in which the size, shape or surface properties of a part are changed by removing the excess material. This is in contrast to forming where the material is simply moved. Machining may be accomplished by locally straining the material to fracture through the relative motion of a tool and the work piece as is done in the conventional processes. However the material removal mechanism may be chemical, electrical or thermal as in the case of the unconventional processes such as chemmilling, electrolytic or electroarc machining respectively.

Metal cutting is frequently called "chip making" because a sharp hardened cutting tool shears and tears the metal, from the surface of the part in the form of chips. Lathe turning, milling, drilling, shaping, planning, broaching, and sawing are typical metal cutting processes.

Abrasive grinding - traditionally - has been regarded as slower but more gentle than metal cutting. However recent im­provements in abrasive wheels and machine design have made some grinding machines as efficient as metal cutting machines.

Grinding is suited for removing metal from hardened and hard-to-cut metals. Whereas some metals work harden when they are machined by a metal cutting process, such metals do not react when they are machined by abrasive grinding. As a rule, grinding processes can hold closer tolerances than metal cutting processes. But part size, configuration, and raw material often determine how precisely a part can be machined.

Machining is a relatively expensive process that should be specified only when high accuracy and good surface finish are required, which, unfortunately is necessary for almost all mating parts.

More than 80% of all manufactured parts must be machined before they are completed, ideally, these parts should be designed so that they can be machined easily and economically. From a design standpoint, understanding how to design parts that can be machined easily is a matter of understanding what the various machine tools are and how they remove metal from the workpiece.

Завдання 7. Знайдіть, де в тексті говориться про такі процеси обробки

chemmilling; electrolytic machining; electro arc machining.

дайте визначення цих понять.

Завдання 8. Визначте. чи е в тексті така інформація:

1. Some metals can't be machined by a metal cutting process

as they work harden in this case.

2. The first metal cutting machine tool was a horizontal boring mill,

3. Abrasive grinding is one of the most common means of machining metals.

4. There are different kinds of abrasive grinding used in industry.

5. Machining is very important for our industry because 4/5 (four fifths) of all manufactured parts should be Machined.

Завдання 9. Виберіть правильний варіант продовження поданих нижче речень у відповідності до змісту тексту.

1. The most common means of metal removal are:

а) turning and milling.

б) cutting and grinding.

в) drilling and boring,

2. Grinding is suited for removing metal from:

а) brittle metals.

б) soft metals.

в) hard-to-cut metals.

3. Abrasive grinding has been traditionally regarded as:

а) a process of chip-making,

б) suitable for processing hardened and hard-to-cut metals.

в) slower but more gentle than metal cutting,

Завдання 10. Знайдіть в тексті відповіді на такі запитання:

1, What are the most common means of metal removal?

2. What are the names of the typical metal cutting processes?

3. What is the difference between metal cutting and abrasive grinding?

4. What is the name of the tool used for abrasive grinding?

5. What is the reason for using abrasive grinding-instead of metal cutting?

6. What is the role of machining in modern industry?

Завдання 11. Дайте кілька варіантів заголовків тексту, які передавали б його

основний зміст.

Завдання 12. Дайте повне визначення поняття "machining",

Завдання 13. Випишіть ключові слова з тексту.

Завдання 14. Складіть план усного повідомлення за змістом тексту 6А.

Завдання 15. Зробіть усне повідомлення за змістом тексту 6А користуючись планом.

Завдання 16. Користуючись словником, прочитайте та перекладіть текст 1Б.

TEXT 1Б

The history of metal cutting dates from the latter part of the 18th century. Before that time machine-tools did not exist.

Although James Watt designed a steam engine with a separate condenser in 1775. It took 25 years to make it - even with the help of one of England's best machine - builders. One of his greatest difficulties was the boring of the cylinder casting.

His first cylinder was manufactured from sheet metal but it could not be made steam tight - even attempts to fill the gap between the piston and the cylinder with cloth, leather or tallow were of no avail.

The problem was eventually solved by John Wilkinson when he invented the horizontal boring mill. This consisted of a cutting tool mounted on a boring bar which was supported on bearings outside the cylinder.

The boring bar could be rotated and fed through the cylinder thus generating, with the tool points, a cylindrical surface independent of the irregularities of the rough casting. This boring mill was the first effective machine tool and it enabled James Watt to produce a successful steam engine.

In this day it was considered a major achievement when a cylinder was bored so that "when a piston was tightly fitted at one end, a clearance not greater than the thickness of a shilling was present at the other end." Today cylinders can be bored to an accuracy of a thousandth of an inch (0.001 in) without much difficulty and with care to a ten - thousandth of an inch (0.0001 in).

Metal cutting as we know is now started with the introduction of this first machine-tool. Today machine-tools and metal cutting form the basis of our industry and metal cutting features either directly or indirectly in the manufacture of all products of our modern civilization. It is not surprising; therefore, that much research effort has been expended in the past in understanding the nature of the cutting process and developing improved cutting techniques.

Завдання 17. Прочитайте i дайте українські еквіваленти таких слів та словосполучень:

а) to bore, boring, cylinder, piston, research, to mount, bearing, to support, to rotate, rough, achievement, clearance, to feed, irregularity;

б) steam-tight; steam engine; to solve a problem; horizontal boring mill; boring bar; tool point; cylindrical surface; cutting techniques: sheet metal; machine-builder, bored to an accuracy of a thousandth of an inch.

Завдання18. Визначте, які з поданих нижче речень відповідають змісту тексту;

1. Metal cutting was widely used already at the beginning of the 18-th century.

2. The first metal cutting machine tool was invented by James Watt in 1775.

3. John Wilkinson invented the first horizontal boring mill.

4. This boring mill enabled James Watt to solve the problem of making his cylinder steam-tight.

5. Today machine tools and metal cutting are not very important for industry.

Завдання 19. Виправте хибні твердження, подані в завданні 18.

Завдання 20. Дайте заголовок до тексту 6Б.

Завдання 21. Складіть план переказу тексту 6Б та перекажіть текст.

Завдання 22. Перекладіть подані нижче фрагменти речень, звертаючи увага на форму присудка – пасивний стан . Потім змініть форму присудка на активний стан , зробивши усі інші необхідні зміни в реченнях:

his first cylinder was manufactured from sheet metal,…… ;

It could not be made steam-tight........: the problem was solved by John Wilkinson,…….; the boring bar was supported on bearings........; the boring bar could be rotated and fed through the cylinder........; much research effort has been expended........ .

Завдання 23. Підготуйте письмове повідомлення на тему:” Деякі факти з історії розвитку обробки металів різанням та її місце у сучасній промисловості” (Обсяг 1000 тис. знаків).