Task 4. Read the text again and decide whether the following statements are true or false. Correct the false statements.

1) Two or more gears working in tandem can produce a mechanical ratio.

2) A gear can also mesh a rack, thereby producing rotation instead of translation.

3) Pinion is smaller than a gear.

4) Technically bevel gear is the same as Herringbone gear.

5) Only nonferrous alloys, cast irons and powder-metallurgy are used in the manufacture of gears.

6) All gears can be shaped, broached, cast, and in the case of plastic gears, injection molded.

7) A quench press is used for large gears that are prone to warp.

Statement
T
F

Task 5. Discuss with your partner:

a) The new information you have got from the text.

b) Your own experience in using gears.

This is how we express our opinion in English. Study this table.

HOW TO EXPRESS OPINION: I think (that)… I consider (that)… I believe (that)… In my opinion … From my point of view … To my mind … As I see it … It seems to me … As for me … I guess …

 

Task 6. Listen to the description of gears and try to describe the main principle of gearing process. Give your own example of using gears.

Task 7. Answer the following questions based on the listening from Ex.6:

1) What is a gear?

2) What types of gear can you name?

3) How can two gears contact with each other?

4) The number of gear rotations is different, isn't it?

5) Smaller gears rotate slower than bigger gears, don't they?

6) What is mechanical advantage?

7) How can gears help to bypass the ship through a dam?

Task 8. Fill in the table. Name the types of gears and describe the main principle of their operation. Use the words from the box.

bevel gear double-helix gear spur gear ring spur worm gear helical gear helical rack face gear hypoid (spiral bevel) gear pinion rack

Name	Definition	Name	Definition
1) ____________		6) ________
2)____________		7) ________
3) __________		8) ________
4)___________		9) ________
5) ____________		10)_______

 

Task 9. What measuring instruments do you know? List as many as you can. Compare your list with those of your groupmates.

Task 10. Try to describe the process in the picture. The following words and word-combinations may help you:

the vertical/horizontal scale, to rest upon the top of the tooth, caliper, geared-wheel, as shown, to jaw, to determine, pitch circle, measurement, chordal thickness and addendum.

 

Task 11. Cross out the word that does not correspond to the other words in the line.

1) spur, bevel, line, helical;

2) depth, death, height, distance;

3) circle, circumference, round, scale;

4) movement, translation, rotation, oscillation;

Task 12. Look at the picture. Try to give the definition to all gear parts.

Working depth –

Whole depth –

Clearance –

Dedendum –

Addendum –

Task 13. Fill in the gaps with proper words from the box. Use each word only once:

important, stock, reduced, figures, to be left,

conditions, measured, shaving, shaper, employed

 

Proper stock allowance is 1) _______ for good results in shaving operations. If too much 2)_______ is left for shaving, the life of the shaving tool is 3)_______ and, in addition, shaving time is increased. The following 4)_______ represent the amount of stock 5)_______ on the teeth for removal by shaving under average 6)________: For diametral pitches of 2 to 4, a thickness of 0.003 to 0.004 inch; for 5 to 6 diametral pitch, 0.0025 to 0.0035 inch; for 7 to 10 diametral pitch, 0.002 to 0.003 inch.

The thickness of the gear teeth may be 7)________ in several ways to determine the amount of stock left on the sides of the teeth to be removed by 8)_______. If it is necessary to measure the tooth thickness during the preshaving operation while the gear is in the gear 9)_______ or hobbing machine, a gear tooth caliper or pins would be 10)_______.

 

Task 14. Match the beginning of the sentence with its ending.

	beginning		ending
1.	When the preshaved gear can be removed from the machine for checking,	a)	without backlash with a gear of standard tooth thickness and the increase in center distance over standard is noted.
2.	the center distance between the two gears	b)	on the basis of the geometrical mean of the size ranges.
3.	Double helical or herringbone gears are commonly	c)	are basic to helical gear calculations.
4.	In this method, the preshaved gear is meshed	d)	the center distance method may be employed.
5.	The values listed in this table are computed	e)	used in parallel-shaft transmissions.
6.	The rules and formulas in the following table	f)	exceeds the standard center distance.

Task 15. Read the following article and write an abstract (120 words) of it.