Exercise 1

Exercise 2

Read the text and learn the words in bold


Screws and bolts are made in a wide range of materials, including brass, bronze, aluminium and titanium as well as steel. They consists of a shaft with thread and a head that may come in a variety of shapes, including round, flat, oval, button, or cap. The vast majority of screws have right-hand thread, which means they are tightened by clockwise rotation. Occasionally, screws have aleft-hand thread, such as the left-hand pedal on a bicycle.
Machine screws come in a range of sizes, and around 85% of all screws and bolts are designed tounified thread dimensions. They are categorised according to their diameter and pitch, or number of threads per inch. ISO metric screw thread is the most popular standard and has displayed previous systems, but there are other common systems, including the British Standard Whitworth, BA system ( British Association ) and the SAE Unified Thread Standard.

 

Exercise 3

 

Exercise 4

Exercise 5

Correct grammar mistakes in the following sentences

1 Switch on the electricity supply in the mains.

2 Before to start the machine, ensure the levers are disengaged.

3 Always you stop the machine before changing gear.

4 The speed can be varied as it required.

5 Without screws, modern industry would not be possibility.

 

Now check your answer.

 

Exercise 6

 

Exercise 7

 

Exercise 8

Some of these words are spelled incorrectly. Correct them.

a solder                                               i parallel

b sipray                                               j airflow

c circuit                                                k ventilation

d conducter                                         l airsol

e componenets                                  m greese

f paritcel                                             n solvent

g horizontal                                        o crackid

h exces

 

Check your answer here.

 

Exercise 9 

Nuts, bolts and screws afford a convenient means of holding components together and also allow them to be easily dismantled.

External (Bolt) threads

External threads are cut on to metal rods using a die made of hardened and tempered cast steel. The die is held in a diestock by means of screws that can be adjusted to increase or decrease the cut of the die.

The diameter of a tap is fixed and when making a nut and the internal thread is cut first. Dies are adjustable and as the external thread is cut on the bolt the diameter is gradually reduced to fit the nut.

Great care must be taken to start the thread true; the metal must be in vertical position in the vice and the die, at right angles to its axis. Suitable lubricants help the cutting. A tap and die should be turned forwards for a full turn and then turned backwards for a quarter - turn in order to break the cutting. If the waste is allowed to clog the die it breaks off the crest of the thread and an interior job results.

Internal (NUT) threads

Threads are cut in the "wall" of a hole with a tap. The process is called tapping. The taps are made of hardened and tempered cast steel and are supplied in threes.

The first to be used is called a taper tap and is tapered at the end; this enables it to get started and begin to cut. The second is used after the taper tap, and has a smaller taper. The third is called a bottoming tap (or sometimes plug tap) and is used to thread to the bottom of a blind hole (i.e. holes that do not go right through the metal). The taps are very brittle and will break if too much force is used.

Before cutting an internal thread hole a suitable hole must be drilled first. The tapping hole size must be smaller than the screw diameter, so that the threads can be cut into the walls.