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.

Getting into shape: some basics

If you think about it, the number of different things you can do to a raw material to get it into a desired shape is pretty limited.

You could melt or liquefy the raw material and pour it into a mould that replicates the shape you want – as if making ice-cubes. You could squeeze, squash, hammer or stretch the material into its required shape – similar to modelling with clay or Plasticene, or rolling-out a piece of dough. You could start with a lump of raw material and cut it to shape, in the same way Michelangelo transformed a block of marble into the statue of David.

Finally, you could assemble your shape by taking different pieces and joining them together using any number of joining methods: screwing, nailing, gluing, welding or stitching for example – innumerable products are made in this way, ranging from clothing to cars and from computers to aircraft.

So, starting with a given mass of raw material, whether it is a pile of granules of plastic, an ingot of steel, a lump of clay, a block of stone or whatever, the basic process routes for manipulating it into a specified shape are essentially limited to:

1. pouring, which we will refer to more precisely as casting;

2. squeezing, which we will call forming;

3. cutting, and;

4. joining.

However, it’s not quite as simple as that. To start with, the wide range of engineering materials means that there are many, many variations on each of these process routes. So far we have principally considered materials just to be ‘stuff’ that has a series of properties. We have seen that these properties vary from material to material but we have not really started to think about why they vary. We are not going to go into the material science behind this in any real depth in this course but what is important to realise is that materials, and hence products, exist on a whole series of size scales. We are all familiar with the sizes of tangible products ranging from a teacup all the way up to a suspension bridge or the Millennium Dome! We can call this scale macro structure. You should also be familiar with the concept that the properties of materials are controlled by the type and arrangement of their individual atoms and molecules, usually called atomic structure. Much of materials science and engineering is concerned with a size scale in between, too small to be seen with naked eye, but much larger than individual atoms and molecules. This middle ground is termed microstructure.

The properties of solid materials can be profoundly influenced by their microstructure and because the microstructure is often changed by processing, the properties of materials, and hence products, are dependent on how they are processed.

Even where a particular type of material and process combination is feasible, it could just be hopelessly uneconomic to contemplate it as a manufacturing option. Finally, the shape of the product is also important. Some manufacturing methods are better suited to particular shapes than others. Indeed, the shape of a product is a good attribute to begin with when deciding which processes are feasible. So one of the first things we must do is think about how we describe shape.

Task 16. Translate the following sentences into Ukrainian:

1 . The teeth of hypoid gears are 1.5 to 2 times stronger than those of spiral bevel gears of the same dimensions, made from the same material.

2. Hypoid gears are similar in general form to bevel gears, but operate on axes that are offset.

3. Beneficial results from a wear standpoint are obtained by making the pinion harder than the gear.

4. The pinion, having a lesser number of teeth than the gear, naturally does more work per tooth, and the differential in hardness between the pinion and the gear serves to equalize the rate of wear.

5. The problem is to design gears capable of transmitting a given amount of power at a given speed, safely and without excessive wear; hence, the required proportions must be determined.

Task 17. Watch the video file “Gears Cutting and Manufacturing”. Try to remember all stages of this process. Write a report (100-120 words) of gears manufacturing using all of the following words:

mechanical components, rotation, linear motion, machining, hobbing, cutting, shaping, blank, reciprocating cutter, lubrication, rack shape cutter, cam, broaching, milling, internal and external gears, gashing, heat treatment, surface finishing.