III. Speak about machine tools according to the plan.

1. What machine tool is it?

2. What is it used for?

3. What is the principle of its work?

4. Could you provide some more information about it?

5. In what does it differ from other similar machine tools?

6. Where this machine tool can be used?

7. What are the drawbacks of it?

 

Text 10

THE LATHE

The modern lathe is a development of one of the earliest machine tools. It has played an important part in the growth of modern industry and mass-production. Today lathes can be completely auto­mated, i.e. produced with computer numerical control (CNC), and require minimum attention from their operators.

The engine lathe is the oldest and most common turning machine. It is used for shaping the external surface of a cylindrical part by rotating the workpiece against a cutting tool. The turret lathe carries a number of cutting tools that can be used in sequence to shape, drill, bore, ream, and cut threads on both exterior and interior cylindrical surfaces. A fully automated turning machine can feed in the work-piece and perform all cutting operations. A duplicating lathe can replicate quantities of an identical shape by using a tracing mecha­nism and a template.

Drilling, boring, making threads, knurling and screw-cutting are other operations that can be carried out on this versatile machine, producing work of very high precision.

The basic principle is simple. The work is fixed by some means to a spindle driven by an electric motor. As the metal revolves at speed, cutting tools are brought into contact with it and the waste is cut away. If the tool travels parallel to the spindle axis cylindrical forms are made. If the tool cuts at right angles to the axis, flat surfaces are produced. At any tool position between 0°-90° to the axis, tapers or conical forms result.

 

Words and word combinations

computer numerical control (CNC) –числове програмне управління (ЧПУ)

the engine lathe – фасонний токарний верстат

cutting operations – токарні операції

a template – шаблон

knurling – нанесення насічок

a spindle – шпиндель

0°-90° – from zero to ninety degrees

EXERCISES

I. Find the Gerund and state its function.

1. The device for measuring the strength of current is called ammeter.

2. He succeeded in performing the experiment.

3. We can increase the current by reducing the resistance of the circuit.

4. We didn't know of his having made the experiment.

5. Wash minor wounds and grazes with soap and water and follow this by applying an adhesive dressing.

6. By analyzing the brightness of the lumi­nescence they estimated the amount of bacteria in the leaf.

7. The analysis of the phenomenon was very useful in helping us to understand the ways Qf nature and our ways of looking at it.

8. Airplanes and helicopters can become highly electrically charged either from flying through dast or snow or from encountering strong electric fields in clouds.

II. Explain the meaning of the international prefixes. Give the Ukrainian equivalents.

• co-author, co-worker, co-operation
• antiparticle, antipathy, antidote
• decode, degenerate, dehydrate, depopulate
• extravagant, extracellular, extraordinary
• ex-president, ex-king, exchange, export
• prefabricate, predecessor, predestine, prearrange
• supernatural, superstructure, superhard
• transform, transplant, translocation
• ultradense, ultramodern, ultra-short

 

 

Text 11

LATHE TOOLS

All machine tools that use metal to shape metal have similar parts to carry out the shaping process: a tool-holder, to keep the shaping tool in place; and a work holder, called a table or compound slide, to hold the part that is to be shaped and to move or feed it at a fixed speed against the tool. In some machines the table is stationary, and the tool moves. In addition, a means of controlling the rate and angle at which the tool cuts the work-piece must be provided. Both the speed of feed and the position of the work-piece and the tool in relation to each other can be varied. Cutting tools must be made of materials that are harder than the metals and are capable of main­taining their cutting edge at friction temperatures that result from the cutting operation. The most common materials used are high-speed steel (H.S.S.); non-ferrous metals containing tungsten, chromium, and cobalt; ceramicized aluminum oxide; and diamonds.

Round-nosed tools (see picture below) give a fine finish whilst knife tools are necessary to work sharp corners. Grinding lathe tools demands great care and skill since the angles – top rake and clearance – have to be correct for each of the different kinds of metal being turned.

For efficient cutting, the cutting edge of the tool has to be aligned carefully with the axis of the work up to the centre line. To reduce overheating, tool wear and to lubricate the cutting area, coolants are often used when turning. Water and soluble oil mixed to a milky-looking solution is commonly used.

There are various ways of setting up the lathe. For facing-off a three or four-jaw chuck is used. Parallel turning on long lengths is carried out between centres, the material being supported at both ends. For holding irregular shaped work, a face plate is used.

 

Words and word combinations

a tool-holder = the tool post – різцетримач

compound slide – супорт

сutting tools = tools – різці

high-speed steel (H.S.S.) – швидкоріжуча (інструментальна) сталь

grinding lathe tools – шліфувальні (абразивні) токарні інструменти

setting up – налагодження

facing-off – обточування торця

chuck – зажимний патрон

centres – центрові отвори

a face plate – планшайба

EXERCISES