In power machining operations there must be a relative movement between cutting tool and workplace. During some machining operations the workplace moves; in others only the cutting tool moves; frequently both tool and workplace are in motion. The various machining operations that employ cutting tools use either a rotating or a traversing motion.
In certain cases an operation is accomplished by the motion of the tool on one machine and by motion of the workplace on another machine. An example is a drilling operation performed on a turret lathe; the drill is traversed without rotating, while the workplace revolves. Had the operation been done on a drill press, the workplace would have remained stationary while the drill rotated as a advanced into the work.
Many particular machining operations can be performed on a workplace most easily or most economically by a certain machine tool, although it is frequently possible to perform the operations on more than one type of equipment. Of primary consideration in fitting the job to the machine is the nature of the required operation.
Завдання 7. Прочитайте текст та передайте його зміст рідною новою.
SPEED AND FEED.
Two important considerations are present in the relative movement of the cutting tool and workplace: cutting speed and feed. The cutting speed is the relative surface speed between the work and the tool, cutting speed is commonly given in feet per minute. The feed is the relative amount of motion or travel of the cutting tool into the workplace per revolution, stroke or unit of time.
To obtain high machining efficiency, desired surface-finish, and appreciable tool life, speed and feed must be closely correlated during any machining operation. Many factors affect this relationship, including the type of tool used, its durability, and the rigidity of the machine and tool, as well as the power of, the machine, and the material hardness, and confutation of the workplace. No general rule or equation for the correct feed and speed can
cover all conditions. Some information comes from publications and head books some from, the advice of others, and much from personal experience.
Most manufacturers of machines and cutting tools supply information on recommended feeds and speeds for their particular product. In addition, machine shop handbooks tool used, its durability, and the rigidity of the machine and tool, as well as the power of the machine, and the material hardness, and confiscation of the workplace. No general rule or equation for the correct feed and speed can coverall conditions. Some information comes from publications and head books, some from the advice of others and much from persons: experience.
Most manufactures of machines cutting tools supply information on recommended feeds and speeds for their particular product. In addition, machine shop handbooks (довідник) provide adequate information on feeds and speeds for normal conditions encountered in machining.
Завдання 8. прочитайте текст; користуючись словником випишіть незнайомі слова; зробіть письмовий переклад тексту:
The capacity of a metal to respond to machining is not a basic standard but is relative. Good machinability involves several criteria: long tool life for a given cutting speed, high surface, well-broken-up chips for easy disposal, low-power consumption in removing a given quantity of metal per tool grind, and the removal of each unit of metal at the lowest cost.
Finished metal parts are usually machined to final size and shape from stock previously rough formed by casting, forming, rolling or extrusion. The machining is done with tools having sharp cutting edges made of materials harder than the metal to be cut. There are a variety of machining operations, including turning, boring, facing, shaping and planning with single-point tools; milling flat for formed surfaces with multipoint milling; cutters, originating holes with two-lipped drills; enlarging holes to size with reamers; broaching internal or external surfaces with multitooth broach cutters; arid threading, sawing, and grinding with appropriate tools.
In every machining operation several factors are highly important: the material to be cut, the tool to do the cutting, the fluid to facilitate cutting, the machine tool on which the work is done, and the process. The rated machinability of two or more metals (tools or fluids) may vary for different cutting processes, such as heavy or light turning, milling, drilling, sawing, broaching, or grinding. Almost always one or more objectives must be sacrificed to obtain others.
There is no single rapid test to determine the machinability of a metal, tool, or cutting fluid for commercial use. One type of metal out of several may give the best tool life, but a second may provide better surface quality, and a third may yleld better-broken-up chips or require less power. By keeping - two of the elements, such as tool and cutting fluid, constant and varying the third, metal cut, an optimum combination car be found. Ratings are based on several factors; the relation of cutting speed to tool life for conditions simulating practice cutting forces, gross power, or unit net power (hp/in**3/min) cutting time under constant feeding force in turning, drilling or sawing; surface quality; cutting temperatures at the tool point; heat-power balance of chips removed; torque and thrust in drilling and tapping; and hardness, or strength of the metal being machined.
Завдання 9. Прочитайте текст з метою осягнути його загальний зміст:
Milling machine is a machine for the removal of metal by feeding a workpiece through the periphery of a rotating circular cutter. The multitoothed cutter of a milling machine produces a milled surface as each revolving tooth removes a portion of metal from the passing workpiece.
Milling machines may generally be classed as horizontal or vertical, depending on the power spindle's axis of rotation. A movable, horizontal table holds the workpiece and carries it through the path of the cutter teeth, on the universal mill, the table may also be rotated horizontally; on machines with a universal head, the cutter may be tilted to the desired angle. Milling machines of considerable size may be made for special applications.
Milling cutters may be made from a single piece of steel or they may be composed of a body with attached cutting elements of a harder material. Various cutters are designed to do specific types of milling operations.
Завдання 10. З поданих нижче речень виберіть те яке передає основну ідею тексту:
1. Milling machine, is a member of a large family of metal cutting machine tools.
2. There are two types of milling machines depending or the power spindle's axis of rotation, horizontal and vertical.
3. Milling cutters may be of different design to do specific types of milling operations.
4. Milling machine is a machine used for the removal of metal from the workpiece by a rotating multitoothed cutter.
Завдання 11. Виберіть правильний варіант завершення речень:
1. Milling machines may be horizontal or vertical depending on
a) the milling cutter’s axis of rotation;
b) the table's axis of rotation;
c) the power spindle’s of rotation.
2. Mіlling machines use
a) single-point cutting tools;
b) multipoint cutting tools;
c) multitoothed milling cutters.
3. Milling cutters may be
а) made of a single place of cast iron;
b) made of a single piece of steel;
c) composed of a body with attached cutting elements of a harder material.
Завдання 12. Найдіть в тексті відповіді на такі запитання:
1. Яким чином відбувається фрезерування поверхні - заготовки?
2. Яка будова стола фрезерного верстата?
3. Які характеристики фрези?
Завдання 13. Підготуйте короткі повідомлення-анотації (5-7 речень) на такі теми:
1. History of metal cutting.
2. Machining of metals: its peculiarities and types.
3. Machine tools and their classification.
4. Cutting tools: their types, materials and life.
5. Lubricants or coolants.
6. Types of chip.
7. N/C machining what is it?
Завдання 14. Підготуйте письмову доповідь (обсяг 1,5 тис. знаків) на тему: "Механічна обробка металів"
Куземский Б.М. Англійська мова для інженерів, 2002
Кузик Ф.К. Англійська мова для студентів немовних спеціальностей,2004.
Науково-технічний журнал «World pump», 2001, №.2,3,10,11.
Хекало М.О.,Литвиненко Г.І. Англійська мова для студентів інженерних спеціальностей ,2004.
Ятель Г.П. Англійська мова (поглиблений курс) для студентів технічних вузів,1995.