Speaking

Exercise 5. Answer the questions:

1. What are machine-tools used for?

2. How are most machine-tools driven nowadays?

3. What facilities have all machine-tools?

4. How are the cutting tool and the workpiece cooled during machining?

5. What other machining methods have been developed lately?

6. What systems are used now for the manufacture of a range of products without the use of manual labour?

7. What parts can be made with lathes?

8. How can the cutting tool be moved on a lathe?

9. How is the workpiece clamped in a lathe?

10. Can we change the speeds of workpiece rotation in a lathe?

11. What is numerical control of machine tools used for?

Exercise 6. Read the following text, discuss in pairs the technical characteristics of metalworking lathes.

Metalworking lathes

A metalworking lathe

In a metalworking lathe, metal is removed from the workpiece using a hardened cutting tool, which is usually fixed to a solid moveable mounting called the "toolpost", which is then moved against the workpiece using handwheels and/or computer controlled motors. These (cutting) tools come in a wide range of sizes and shapes depending upon their application. Some common styles are diamond, round, square and triangular.

The toolpost is operated by leadscrews that can accurately position the tool in a variety of planes. The toolpost may be driven manually or automatically to produce the roughing and finishing cuts required to turn the workpiece to the desired shape and dimensions, or for cutting threads, worm gears, etc. Cutting fluid may also be pumped to the cutting site to provide cooling, lubrication and clearing of swarf from the workpiece. Some lathes may be operated under control of a computer for mass production of parts (see "Computer Numerical Control").

Metalworking lathes are commonly provided with a variable ratio gear train to drive the main leadscrew. This enables different pitches of threads to be cut. Some older gear trains are changed manually by using interchangeable gears with various numbers of teeth, while more modern or elaborate lathes have a quick change box to provide commonly used ratios by the operation of a lever.

The threads that can be cut are, in some ways, determined by the pitch of the leadscrew: A lathe with a metric leadscrew will readily cut metric threads (including BA), while one with an imperial leadscrew will readily cut imperial unit based threads such as BSW or UTS (UNF,UNC).

The workpiece may be supported between a pair of points called centres, or it may be bolted to a faceplate or held in a chuck. A chuck has movable jaws that can grip the workpiece securely.

There are some effects on material properties when using a metal working lathe. There are few chemical or physical effects, but there are many mechanical effects which include, residual stress, microcracks, workhardening and tempering in hardened materials.

Exercise 7. Prepare the brief report about modern lathes.

Section III. Screw Machines

Grammar : Gerund.

Speaking: Screw Machines.

Screw Machines

Study vocabulary:

a screw machine = screw-cutting machine – винтонарезной станок

to turn – точить, обтачивать

a misnomer [mis΄nәumә] – неправильное употребление имени/термина; неправильное имя, название места

CNC (computerized control) – управление от ЭВМ

cam – копир; кулачок; поводковый патрон

screw-cutting lathe – токарно-винторезный станок; резьботокарный станок

turret – револьверная головка (станка)

retron – ритрон

cage – обойма (подшипника); сепаратор

a Gatling Gun – пулемет Гэтлинга Первый американский пулемет (1862), предшественник "максима" [Maxim, The]; назван по фамилии изобретателя [Gatling, Richard Jordan]. Скорострельность – 350 выстрелов в минуту при 5–10 барабанах. Начал использоваться в конце Гражданской войны и находился на вооружении армии США с 1866 по 1911 гг., позже был взят на вооружение многими зарубежными армиями. Активно применялся в борьбе с индейцами. В 20-е гг. XX в. служил основным оружием нью-йоркским и бостонским гангстерам.

a threading die = tapping die – 1) плашка 2) винторезная головка

a die head – 1) матрицедержатель 2) винторезный патрон; винторезная головка

Exercise 1. Study the word-building of the following groups, define the part of speech, give the Russian equivalents:

to turn, turn, turner, turning, turned, turning-along, turning-off

to screw, screw, screwdown, screwdriver, screwhead, screwing

to retron, retronymous, retronymously

to thread, thread, threader, threading

Exercise 2. Match Russian and English equivalents:

1) a screw machine a) винторезный патрон

2) to turn b) ритрон

3) a misnomer c) токарно-винторезный станок

4) cam d) обойма

5) screw-cutting lathe e) неправильное употребление имени/термина

6) turret f) винторезная головка

7) retron g) обтачивать

8) cage h) кулачок

9) a threading die i) револьверная головка

10) a die head j) винтонарезной станок

Exercise 3. Define the Gerund and its function, translate sentences into Russian:

All screw machines are fully automated, whether mechanically (via cams) or by CNC (computerized control), which means that once they are set up and started running, they continue running and producing parts with very little human intervention.

The name “screw machine” is somewhat of a misnomer, because screw machines spend much of their time making things that are not screws and that in many cases are not even threaded.

1. There are many variables involved in answering the question of which is best for a particular part at a particular company.

The outside of the bar is machined to shape (turning operation). The bar is drilled (boring operation) and finally, the part is cut off (parting operation).

It is impractical to reverse the rotation of the spindle[s] of the machine so it is necessary to have a cutting tool that can cut in one direction and cut fast and be removed without interrupting the rotation of the machine.