Obami | Digital Stakeholder Experiences

Formula Sheet - (click and zoom to view)
QUESTION 1 - MULTIPLE-CHOICE QUESTIONS

Marks: 20

Attached Section Resource:

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Question 1:

Avoid using compressed air to clean chips from the milling machine because …

Your Answer:

it does the job too slowly.

flying chips may cause eye injuries.

it gives a poor finish to the job.

it is too expensive.

Question 2:

Before operating a lathe machine, you should …

Your Answer:

remove all safety guards.

oil the area surrounding the machine.

wear rings and jewellery.

make sure you know the location of the ON and OFF switch.

Question 3:

Which hardness tester uses a steel-ball indenter to measure the penetration into a metal under a specified load?

Your Answer:

Webster hardness tester

Rockwell hardness tester

Brinell hardness tester

Vickers hardness tester

Question 4:

A Grade 12 learner uses a multimeter during simulation of a circuit. What can be measured with a multimeter?

Your Answer:

Diode and continuity measurement

Transistor velocity

Length of the conductor

Thickness of the conductor

Question 5:

Carbon steels are identified according to their carbon content percentage. Low-carbon steel contains less than …% carbon.

Your Answer:

0,45

0,3

0,7

1,5

Question 6:

… is added to steel when toughness, hardness and wear resistance are desired.

Your Answer:

Copper

Aluminium

Lead

Tungsten

Question 7:

The lathe operates on the principle of ...

Your Answer:

the cutter revolving against the work piece.

the cutting tool, that can be controlled, can be moved vertically across the work piece.

the work piece rotating against the cutting tool, which can be controlled.

both cutter and work piece rotating.

Question 8:

The largest piece of material that can be turned between centres is equal to the …

Your Answer:

length of the bed minus the space taken up by the headstock.

length of the bed minus the space taken up by the tailstock.

length of the bed minus the space taken up by the headstock and the tailstock.

total length of the bed.

Question 9:

Identify the milling process in FIGURE 1.1 below:

Attached Resource:

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Your Answer:

Gang milling

Slab milling

Straddle milling

Up-cut milling

Question 10:

Ultrasonic inspection techniques use … waves to detect flaws in welded joints.

Your Answer:

air

light

electronic

sound

Question 11:

Which TWO bottled gases are used for the MIG welding process?

Your Answer:

Argon and carbon dioxide (CO2)

Argon and carbon monoxide

Acetylene and oxygen

Oxygen and argon

Question 12:

Which ONE of the following describes Hooke's law?

Your Answer:

Instantaneous force divided by the original cross-sectional area of the test material

Stress value required to produce unit strain in a tensile specimen of the particular material

Strain is directly proportional to the stress causing it, provided the limit of elasticity is not exceeded

A measurement of the deformation produced by the application of the external forces

Question 13:

What is strain?

Your Answer:

Determined by dividing the load by the smallest actual cross- sectional area of the test specimen

The ratio between the original length and the change in length when an external force is applied

The amount of stress that a material can absorb without exceeding its breaking stress

A measurement of the deformation produced by the application of an external force

Question 14:

Where is EP 90 oil used?

Your Answer:

Engine

Power steering

Brakes

Gearbox

Question 15:

Mineral oils ...

Your Answer:

are used where the load, speed and temperature is low.

provide increased heating capacity in some applications.

range from milky to transparent in appearance.

are composed of oil droplets.

Question 16:

A windscreen wiper motor generates rotary motion which is converted into the motion operating the wiper blades. In which motion are the wiper blades operating?

Your Answer:

Rotary

Reciprocating (in straight line)

Oscillating (pendulum motion)

Linear

Question 17:

Identify the type of screw thread in FIGURE 1.2 below:

Attached Resource:

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Your Answer:

V-screw thread

Square screw thread

Acme screw thread

ISO Metric screw thread

Question 18:

What is the stroke length (X) moved by the follower for the pear-shaped cam shown in FIGURE 1.3 below, given that d₁ = 6 mm and d₂ = 12 mm?

Attached Resource:

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Your Answer:

18 mm

24mm

2mm

6mm

Question 19:

A steam turbine is used to ...

Your Answer:

increase the fuel consumption in relation to engine output.

increase the volumetric efficiency of an engine.

drive a generator to generate electricity.

decrease the atmospheric pressure of an engine.

Question 20:

What will the volumetric efficiency be if a 100 mm³ blower displaces 83 mm³ per revolution?

Your Answer:

83%

17%

103%

100%

QUESTION 2 - TOOLS AND EQUIPMENT

Marks: 8

Question 1:

In terms of lathes and milling machines, what does the abbreviation CNC stand for?

Your Answer:

Question 2:

State THREE advantages of a CNC machine.

Your Answer:

Question 3:

State ONE disadvantage of a CNC machine.

Your Answer:

Question 4:

Identify and specify the type of equipment used to test the resistance to bending, scratching, abrasion and/or cutting.

Your Answer:

2.5 - A taxi driver notices that his vehicle loses power. The mechanic will have to conduct a compression test according to certain procedures. Give the reason for carrying out each of the following procedures:

Marks: 4

Question 1:

Removing the high-tension leads

Your Answer:

Question 2:

Unplugging the fuel injectors

Your Answer:

Question 3:

Fully opening the throttle valve

Your Answer:

Question 4:

Recording the readings

Your Answer:

2.6 - FIGURE 2.1 below shows a typical tester used in a mechanical workshop. Answer the questions that follow.

Marks: 8

Attached Section Resource:

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Question 1:

Identify the tester shown in FIGURE 2.1.

Your Answer:

Question 2:

Label the parts of the tester marked A–E.

Your Answer:

Question 3:

State the purpose of the tester shown in FIGURE 2.1.

Your Answer:

QUESTION 3 - MATERIALS

3.1 - The wheel rims on some vehicles are manufactured from mild steel. Others are cast in aluminium alloys. Answer the questions that follow.

Marks: 5

Question 1:

Give THREE reasons for choosing to manufacture vehicle wheel rims out of aluminium alloy.

Your Answer:

Question 2:

Give TWO reasons why the wheel rims of heavy-duty vehicles (trucks) are manufactured from steel.

Your Answer:

3.2 - FIGURE 3.1 below shows tin snips. Answer the questions set on the tin snips.

Marks: 3

Attached Section Resource:

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Question 1:

What material is used to manufacture the blades? Give a reason for your answer.

Your Answer:

Question 2:

Why is it necessary to smear oil on the blades?

Your Answer:

3.3

Marks: 4

Question 1:

Explain why alloys are produced. Give FOUR reasons.

Your Answer:

3.4 - The materials traditionally used in the manufacturing industry are being replaced at an alarming rate by a new generation of materials, like thermoplastics and thermosetting plastics. Answer the questions that follow.

Marks: 6

Question 1:

Explain the difference between thermoplastics and thermosetting plastics.

Your Answer:

Question 2:

Give ONE example of each of the plastics mentioned in the question above.

Your Answer:

3.5

Marks: 2

Question 1:

Why is carbon fibre used in the automotive manufacturing industry? Give TWO reasons.

Your Answer:

QUESTION 4 - SAFETY, TERMINOLOGY AND JOINING METHODS

Marks: 16

Question 1:

Sipho is using a bearing puller to remove bearings from a shaft. List FIVE safety rules for the safe use of a bearing puller.

Your Answer:

Question 2:

Specify FIVE general safety rules to be considered when using equipment like the lathe and drill press.

Your Answer:

Question 3:

Calculate the feed, in millimetres per minute, of an 80 mm diameter milling cutter with 24 teeth operating at a cutting speed of 35 metres per minute and cutting at a feed of 0,02 mm per tooth.

Your Answer:

4.4 - A spur gear with 119 teeth must be machined onto a work piece. Hint: Use (N = 120 and n = 119 divisions) OR (A = 120 and n = 119 divisions) for the calculations. The dividing head ratio is 40 : 1.

Marks: 14

Question 1:

Calculate the indexing needed for the operation.

Your Answer:

Question 2:

Calculate the change gears that must be installed on the dividing head.

Your Answer:

Question 3:

State the direction of rotation of the index plate in relation to the rotation of the index crank handle.

Your Answer:

4.5

Marks: 3

Question 1:

Name THREE types of milling machines.

Your Answer:

4.6 - Explain the functions of the following milling machine components:

Marks: 6

Question 1:

Dividing head

Your Answer:

Question 2:

Index plate

Your Answer:

Question 3:

Spindle on the dividing head

Your Answer:

4.7 - John works for Shai-Welco as a learner welder. Assist John by answering the questions that follow.

Marks: 11

Question 1:

Name TWO causes of slag inclusion in a welded joint.

Your Answer:

Question 2:

Which TWO steps can be followed to prevent undercutting in a welded joint?

Your Answer:

Question 3:

Describe ONE step that can be followed to prevent incomplete penetration in a welded joint.

Your Answer:

Question 4:

What is the difference between a destructive test and a non-destructive test on materials?

Your Answer:

Question 5:

Name FOUR basic components of MIG/MAG welding machines.

Your Answer:

QUESTION 5 - MAINTENANCE AND TURBINES

5.1 - Define the following terms related to motor oils:

Marks: 4

Question 1:

Pour point

Your Answer:

Question 2:

Viscosity

Your Answer:

5.2

Marks: 5

Question 1:

Give FIVE functions of a good motor oil.

Your Answer:

5.3

Marks: 3

Question 1:

Give THREE reasons for using cutting fluid when working on the centre lathe.

Your Answer:

5.4

Marks: 3

Question 1:

Explain the functions of automatic transmission fluid.

Your Answer:

5.5 - Name the type of motor oil and grading that is used in the following systems under South African conditions:

Marks: 6

Question 1:

Internal combustion engine

Your Answer:

Question 2:

Manual transmission

Your Answer:

Question 3:

Automatic transmission

Your Answer:

5.6

Marks: 1

Question 1:

What is the gas turbine also known as?

Your Answer:

5.7 - FIGURE 5.1 below shows the internal components of a turbocharger. Answer the questions that follow.

Marks: 14

Attached Section Resource:

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Question 1:

Label the components of the turbocharger marked A–H in FIGURE 5.1 above.

Your Answer:

Question 2:

Explain the operation of a turbocharger.

Your Answer:

5.8 - Explain the following terms regarding the turbocharger:

Marks: 4

Question 1:

Lag

Your Answer:

Question 2:

Boost

Your Answer:

QUESTION 6 - FORCES AND SYSTEMS AND CONTROL

6.1 - A hydraulic system is used to lift mechanical machines. The specifications of the system used are represented diagrammatically in FIGURE 6.1 below. The system is equipped with the necessary one-way control valves to prevent the fluid from flowing back after each stroke. Determine, by means of calculations, the following: (Show ALL units.)

Marks: 18

Attached Section Resource:

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Question 1:

The fluid pressure in the hydraulic system when in equilibrium

Your Answer:

Question 2:

The force (F) that must be exerted onto piston A to lift the load of 25 kN on piston B

Your Answer:

Question 3:

The distance X, in millimetres, that piston B will move if piston A completes 10 strokes

Your Answer:

6.2 - A load of 45 kN causes compressive stress of 18 MPa in a round brass bar. The original length of the bar is 185 mm and Young's modulus for brass is 90 GPa. Determine, by means of calculations, the following:

Marks: 15

Question 1:

The diameter, in millimetres, of the resistance surface of the round brass bar

Your Answer:

Question 2:

The strain caused by the load

Your Answer:

Question 3:

The change in length, in millimetres, caused by the load

Your Answer:

6.3 - The V-belt drive system of a compressor is shown in FIGURE 6.2 below. The driver pulley of the belt drive system rotates at 2 700 r/min. The driver pulley has a diameter of 210 mm. The compressor shaft must rotate at 1 000 r/min. Determine, by means of calculations, the following:

Marks: 8

Question 1:

The diameter of the driven pulley in mm

Your Answer:

Question 2:

The power transmitted, in kilo magnitude, if the effective force in the belt is 400 N

Your Answer:

6.3 - A single-plate friction clutch has an effective diameter of 0,28 m and is able to transmit 336 Nm of torque. The clutch plate has friction material on both sides with a friction co-efficient of 0,3. Calculate and state the correct units for the following:

Marks: 9

Question 1:

The total applied force needed on the pressure plate

Your Answer:

Question 2:

The power transmitted at 2 800 r/min

Your Answer: