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T580(E)(N17)T NOVEMBER EXAMINATION

NATIONAL CERTIFICATE

FITTING AND MACHINING THEORY N2

(11022032)

17 November 2016 (X-Paper) 09:00–12:00

Calculators may be used.

Candidates will require drawing instruments.

This question paper consists of 9 pages and 1 formula sheet.

(11022032) -2- T580(E)(N17)T

Copyright reserved Please turn over

DEPARTMENT OF HIGHER EDUCATION AND TRAINING REPUBLIC OF SOUTH AFRICA

NATIONAL CERTIFICATE FITTING AND MACHINING THEORY N2

TIME: 3 HOURS MARKS: 100

NOTE: If you answer more than the required number of questions, only the

required number of questions will be marked. All work you do not want to be marked must be clearly crossed out.

INSTRUCTIONS AND INFORMATION 1. 2. 3. 4. 5. 6.

Answer ALL the questions in SECTION A. Answer ONLY TWO questions in SECTION B. Answer either QUESTION 1.1 OR 1.2 of QUESTION 1. Read ALL the questions carefully. Number the answers according to the numbering system used in this question paper. Write neatly and legibly.

(11022032) -3- T580(E)(N17)T


SECTION A QUESTION 1: OCCUPATIONAL SAFETY NOTE: Answer ONLY QUESTION 1.1 OR QUESTION 1.2 1.1 The Occupational Health and Safety Act of 1993 and its applicable

regulations apply. Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (1.1.1–1.1.5) in the ANSWER BOOK.

1.1.1 A ladder should be placed against a wall with its feet a quarter of

its length away from the wall.

1.1.2 Gas cylinders can be lifted by means of electromagnets. 1.1.3 When changing air tools, the quick method of bending the hose

should be used to cut off the air supply.

1.1.4 It is always a good practice to ensure that cool air is supplied at the

intake of a compressor.

1.1.5 Where more than one worker is used to move heavy equipment,

teamwork is extremely important to prevent accidents.

(5 × 1) (5)

OR

1.2 The regulations applicable to the Minerals Act of 1991 apply.

Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (1.2.1–1.2.5) in the ANSWER BOOK.

1.2.1 Illumination of machinery in a mine is not necessary if people are

moving around the machine but not working on it.

1.2.2 Any experienced worker can oil a machine in motion at any time. 1.2.3 First-aid certificates shall be renewed at intervals of not more than

three years.

1.2.4 When an accident causes the death of a person, such a place must

first be inspected by a mining engineer.

1.2.5 If the inspection of an area where a fatal accident occurred does

not take place within three days, the work may continue.

(5 × 1) (5)

[5]

(11022032) -4- T580(E)(N17)T


QUESTION 2: COUPLINGS Couplings are classified into three main groups. 2.1 Name the THREE main groups into which couplings are classified. (3) 2.2 Give ONE example of a coupling that falls into each group listed in 2.1. (3)

[6] QUESTION 3: LIMITS AND FITS 3.1 Give an example of a bilateral tolerance, indicating its basic size and upper

and lower limits.

(1) 3.2 Give an example of a unilateral tolerance, indicating its basic size and upper

and lower limits.

(1) 3.3 List the THREE main classes of fit associated with the ISO schedule of limits

and fits.

(3) 3.4 State the class of fit associated with the following types of fit: 3.4.1 Sliding fit 3.4.2 Shrink fit (2 × 1) (2)

[7] QUESTION 4: BEARINGS 4.1 Give FOUR reasons for the overheating of anti-friction bearings. (4) 4.2 Briefly describe the heating-lamp method of mounting anti-friction bearings. (3)

[7] QUESTION 5: LUBRICATION AND VALVES 5.1 State TWO factors that should be considered when choosing a lubricant for a

specific operation. (2)

5.2 Define the term burning point. (1) 5.3 Name the valves shown in FIGURE 1. Write only the name of the valve next

to the question number (5.3.1–5.3.4) in the ANSWER BOOK.

(11022032) -5- T580(E)(N17)T


FIGURE 1

(4 × 1) (4) [7]

QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND WATER-PIPE SYSTEMS

6.1 The statements below refer to packing, stuffing boxes and joints.

Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (6.1.1–6.1.3) in the ANSWER BOOK.

6.1.1 Packing is used to wrap up seals so that they are ready for use.

6.1.2 A protective cover should be placed over threaded sections to prevent damage to seals.

6.1.3 Asbestos is no longer recommended as a packing material because of its association with health problems.

(3 × 1) (3)

6.2 Name the THREE methods of accommodating expansion and contraction in pipe lines as shown in FIGURE 2. Write only the name of the joint next to the letters (A-C) in the ANSWER BOOK.

FIGURE 2 (3 × 1) (3)

(11022032) -6- T580(E)(N17)T


6.3 Welding and flanging are TWO methods of joining steel pipes.

Name THREE other methods of joining steel pipes.

(3) [9]

QUESTION 7: PUMPS 7.1 Name the THREE categories into which pumps are classified. (3) 7.2 Briefly explain the operation of a gear pump. (3)

[6] QUESTION 8: COMPRESSORS 8.1 State TWO functions of the aftercooler used in compressors. (2) 8.2 Name THREE types of rotary compressors. (3)

[5] QUESTION 9: V-BELT, CHAIN AND GEAR DRIVES AND REDUCTION GEARBOXES 9.1 Explain the following V-belt terms: 9.1.1 Centre distance 9.1.2 Arc of contact (2 × 1) (2) 9.2 Give TWO reasons why an intermediate gear is used in a gear drive. (2) 9.3 Name FOUR basic components of a single reduction gearbox. (4)

[8]

TOTAL SECTION A: 60

(11022032) -7- T580(E)(N17)T


SECTION B

Answer only TWO of the questions in SECTION B. QUESTION 10: HYDRAULICS AND PNEUMATICS 10.1 Explain the function of a check valve in a hydraulic system. (1) 10.2 Make neat free-hand sketches of the ISO symbols representing the following

pneumatic components:

10.2.1 Throttle valve 10.2.2 Check valve 10.2.3 Receiver/tank 10.2.4 Dryer 10.2.5 Filter (5 × 1) (5) 10.3 Name SIX types of valves that you would find in hydraulic systems. (6) 10.4 State FIVE basic aspects of inspection in the routine maintenance of a

pneumatic circuit.

(5) 10.5 List THREE main functions of a directional control valve in a hydraulic circuit. (3)

[20] QUESTION 11: CENTRE LATHES

11.1 Explain the function of a mandrel. (1)

11.2 State THREE advantages of using a mandrel on a lathe. (3)

11.3 Name the THREE basic instructional forms used on a CNC lathe. (3)

11.4 Explain the difference between absolute programming and incremental programming used on CNC lathe.

(2)

11.5 A two-start square thread with a 5 mm pitch is to be cut on a lathe. The pitch diameter of the thread is 100 mm and the clearance angle is 3º. Calculate:

11.5.1 The helix angle of the thread (3)

11.5.2 The lead angle of the cutting tool used. (1)

11.5.3 The following angle of the cutting tool used (1)

(11022032) -8- T580(E)(N17)T

Copyright reserved

11.6 11.6.1 Briefly explain how the travelling steady operates on a centre lathe.

11.6.2 Briefly explain how the fixed steady operates on a centre lathe.

(2 × 2) (4)

11.7 One method of cutting a taper on a centre lathe is the compound slide method.

11.7.1 State ONE advantage of using the compound slide method.

11.7.2 State ONE disadvantage of using the compound slide method.

(2 × 1) (2) [20]

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS

12.1 There are FOUR methods of indexing using dividing head on milling machines.

12.1.1 Name the FOUR methods of indexing (4)

12.1.2 State the circumstance under which each of the indexing methods listed in 12.1.1 will be used.

(4)

12.2 Explain the purpose of the dividing head. (2)

12.3 A work piece must have 13 gear teeth machined on its circumference.

12.3.1 What type of indexing would you perform on this gearblank? (1)

12.3.2 Give a reason for the answer in QUESTION 12.3.1. (1)

12.3.3 Calculate the required indexing, using a Cincinnati dividing head table, as shown below.

(3)

The Cincinnati Dividing Head

Side 1 24 25 28 30 34 37 38 39 41 42 43

Side 2 46 47 49 51 53 54 57 58 59 62 66

12.4 Grinding wheels have markings for identification purposes.

List the FIVE factors by which you would identify a grinding wheel.

(5) [20]

TOTAL SECTION B: 40

GRAND TOTAL: 100

(11022032) T580(E)(N17)T

Copyright reserved

FITTING AND MACHINING THEORY N2 FORMULA SHEET

tf = f T N

π D NS =

60

S = π D n

40

N

N

9

D - d length of workpieceSet-over =

2 length of taper

length of workpieceSet-over = Ratio

2

θ Xtan =

2 L

Leading angle = 90 - (Helix angle + clearance angle)

Foll

owing angle = 90 + (Helix angle - clearance angle)

Lead = No. of starts pitch

PitchMean diameter = OD -

2

Leadtan θ =

Mean circumference



NOVEMBER EXAMINATION


17 NOVEMBER 2016

This marking guideline consists of 9 pages.

MARKING GUIDELINE

MARKING GUIDELINE -2- T580(E)(N17)T FITTING AND MACHINING THEORY N2


SECTION A: ALL QUESTIONS ARE TO BE MARKED IN THIS SECTION QUESTION 1: OCCUPATIONAL SAFETY 1.1 1.1.1 True 1.1.2 False 1.1.3 False 1.1.4 True 1.1.5 True

(5 × 1) (5)

OR 1.2 1.2.1 False 1.2.2 False 1.2.3 True 1.2.4 True 1.2.5 True

(5 × 1) (5) [5]

QUESTION 2: COUPLINGS 2.1 Rigid or permanent or fixed couplings

Flexible couplings

Self-aligning couplings

(3) 2.2 Rigid or fixed

Flange

Marine

Chain

Gear

Fluid (Any 1)

(1)

Flexible

Raffard

Pin and rubber bush

Rubber belt

Spider

Nylon

Sleeve

Metal disc (Any 1)

(1)

Self-aligning

Universal joint

CV joint

Hooke's joint (Any 1)

(1) [6]



QUESTION 3: LIMITS AND FITS 3.1

(1) 3.2

(1) 3.3 Interference fit

Clearance fit

Transition fit

(3) 3.4 3.4.1 Clearance 3.4.2 Interference (2 × 1) (2)

[7] QUESTION 4: BEARINGS 4.1 Insufficient lubricant/Excessive lubrication

Abrasive or corrosive contaminants in the bearing

Incorrect bearing clearances

Raceways turning

Incorrect grade of oil

Bearing fitted wrongly

Foaming oil (Any 4 × 1)

(4) 4.2 Raise the bearing so that the heating lamps supply heat from underneath.

Heat to the desired temperature. Fit the bearing as soon as possible.

(3) [7]

QUESTION 5: LUBRICATION AND VALVES 5.1 Speed between moving parts

Operating temperature

Load on the bearing

Cost of lubricant

Environmental conditions

Clearance between components

Pressure between the moving parts (Any 2 × 1)

(2) 5.2 The temperature at which a lubricant gives off enough vapour to burn

continuously when ignited.

(1)



5.3 5.3.1 Diaphragm valve 5.3.2 Pressure relief valve 5.3.3 Butterfly valve 5.3.4 Ball valve

(4 × 1) (4) [7]

QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND WATER-PIPE SYSTEMS 6.1 6.1.1 False 6.1.2 True 6.1.3 True

(3 × 1) (3) 6.2 A. Expansion diaphragm

B. Corrugated expansion joint C. Telescopic expansion joint/Packed expansion joint

(3 × 1)

(3) 6.3 Screwed

Bell and spigot

Butt and strap

Threaded union

Brazed/Soldered (Any 3 × 1)

(3) [9]

QUESTION 7: PUMPS 7.1 Centrifugal pumps

Reciprocating pumps

Rotary pumps

(3) 7.2 As the gear teeth unmesh, a vacuum is created at the inlet. Fluid flows in

the spaces between the gear teeth. As the gear teeth mesh again at the outlet, the fluid is forced out.

(3) [6]

QUESTION 8: COMPRESSORS 8.1 Cools the air after compression

Dries the air before entry into the receiver (2 × 1)

(2)



8.2 Vane compressor

Rotary screw compressor

Lobe compressor

Single- or Multi-stage centrifugal compressor (Any 3 × 1)

(3) [5]

QUESTION 9: V-BELT, CHAIN AND GEAR DRIVES AND REDUCTION GEARBOXES 9.1 9.1.1 It is the distance between the centre of the drive pulley and the

centre of the driven pulley.

9.1.2 It is the angle made by the amount of contact the belt makes over

the circumference of the pulley, the vertex being at the centre of the pulley.

(2 × 1) (2) 9.2 To change direction of the final drive

To alter or change the centre distance between the driver and driven gears

(2)

9.3 Casing

Output shaft

Input shaft

Pinion or driver gear

Driven gear (Any 4 × 1)

(4) [8]

TOTAL SECTION A: 60



SECTION B ONLY TWO QUESTIONS ARE TO BE ANSWERED IN THIS SECTION. QUESTION 10: HYDRAULICS AND PNEUMATICS 10.1 It maintains fluid flow in one direction only. (1) 10.2 10.2.1

10.2.2

10.2.3

10.2.4

10.2.5

(5 × 1) (5) 10.3 Check valve

Direction control valve

Pressure relief valve

Throttle valve

Pressure reducer valve

Flow control valve (Any 6 × 1)

(6) 10.4 Check the oil level in the compressor.

Ensure that air supply is as pure and cool as possible.

Open the drain valve to release any moisture.

Keep the intake filter clean.

Check hoses and fittings for leaks.

Document all inspections in the log book.

Inspect the receiver for any air leakages. (Any 5 × 1)

(5) 10.5 It controls the direction of flow.

It controls the energy of flow.

It opens or closes the path of flow.

(3) [20]



QUESTION 11: CENTRE LATHES 11.1 A mandrel is a work-piece holding device.

A mandrel is used to hold a work piece which has already been bored or reamed.

(Any 1 × 1)

(1) 11.2 It saves time as setting up is simple.

Concentricity is guaranteed.

Batch production is possible.

Mandrels can be modified to suit later work.

Setting up can be done by unskilled operators.

Can be adapted to suit a large variety of workpieces. (Any 3 × 1)

(3) 11.3 G-commands

M-commands

Positional data

(3) 11.4 In absolute programming all tool movement from a fixed point or common

reference point whereas in incremental programming each tool movement is made with reference to the previous or last position.

(2) 11.5 11.5.1

10

Lead =No.of starts×Pitch

=2×5

= mm

10

Leadtanθ =

Pitch circumference

=π×100

= 0,0318

-1θ = tan 0,0318

=1,82°

(3)

11.5.2

85,18

Leading angle = 90°- helix angle + clearance angle

= 90°- 1,82°+3°

= mm

(1)

11.5.3

88,82

Following angle = 90° + helix angle - clearance angle

= 90° + 1,82°-3°

= mm

(1)

√

√

√

√

√

√

√

√

√

√



11.6 11.6.1 The travelling steady is fixed against the cross slide to support long

and slender work pieces between the lathe chuck and tail-stock centre. It follows the cutting tool and thus reduces unnecessary vibration.

11.6.2 The fixed steady is fixed to the bed of the lathe to support a big-

diameter shaft in the chuck. Now machining can be done at the end of the shaft, like cutting inside screw thread or making a hole for a bearing.

(2 × 2)

(4) 11.7 11.7.1 Short tapers can be turned at any angle

Internal and external tapers can be turned

Operations and calculations are simple (Any 1 × 1)

(1)

11.7.2 No auto feed

Finish cannot be guaranteed

The length of the taper is limited to the travel of the compound slide

Not accurate (Any 1 × 1)

(1) [20]

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 12.1.1 Rapid indexing

Simple indexing

Angular indexing

Differential indexing

(4)

12.1.2 Rapid indexing will be used when the number of grooves or teeth

required is exactly divisible into 12, 24 or 36. Simple indexing will be used when the number of grooves or teeth required is not exactly divisible into 12, 24 or 36 and rapid indexing cannot be used. Angular indexing will be used when the spacing required is given as an angle, in degrees. Differential indexing will be used when the number of grooves or teeth required is a prime number and no index plate is available.

(4) 12.2 To cut evenly spaced holes, slots or teeth on the circumference of a shaft (2)



12.3 12.3.1 Simple indexing (1) 12.3.2 The number of teeth required is NOT exactly divisible into 12, 24 or

36, so rapid indexing cannot be used. Therefore simple indexing can be used.

(1) 12.3.3

13

3

13

1

40 40Indexing = =

N

1=

13

= turns and of a turn13

3 3× =

13 3 39

Select the 39-hole circle of Side 1 of the Cincinnati index plate 3 full turns of the crank handle and 3 holes in a 39-hole circle

(3) 12.4 Abrasive type

Grade of wheel

Bonding material

Grain size

Structure

(5) [20]

TOTAL SECTION B: 40

GRAND TOTAL: 100

√

√


T640(E)(M30)T

APRIL EXAMINATION



(11022032)

30 March 2016 (X-Paper) 09:00–12:00

Calculators and drawing instruments may be used.


(11022032) -2- T640(E)(M30)T





NOTE: If you answer more than the required number of questions, only the required

number of questions will be marked. All work you do not want to be marked must be clearly crossed out.


Answer ALL the questions in SECTION A. Answer either QUESTION 1.1 or QUESTION 1.2 of Question 1. Answer only TWO questions in SECTION B. Read ALL the questions carefully. Number the answers according to the numbering system used in this question paper. Write neatly and legibly.

(11022032) -3- T640(E)(M30)T


SECTION A QUESTION 1: OCCUPATIONAL SAFETY 1.1 List FIVE factors to consider when constructing safety guards on machinery. [5] OR 1.2 Describe what is meant by: 1.2.1 Illumination of machinery 1.2.2 Approved lamps in fiery mines and coal mines 1.2.3 Inspection and testing of boilers 1.2.4 Unprotected electrical cables 1.2.5 Lights to be carried (5 x 1) [5] QUESTION 2: COUPLINGS State FIVE advantages of using short shafts joined by couplings instead of long shafts. [5] QUESTION 3: LIMITS AND FITS 3.1 Explain the meaning of the following terms used in connection with limits and

fits:

3.1.1 Hole basis systems 3.1.2 Minimum allowance 3.1.3 Bilateral tolerance 3.1.4 Transition fit (4 x 1) (4) 3.2 A shaft is to be fitted into a bush. The following sizes are given for the shaft

and the bush:

Shaft : 0,0250,03530

Bush : 0,0250,01530

3.2.1 Determine the minimum allowance of the fitted parts (3) [7]

(11022032) -4- T640(E)(M30)T


QUESTION 4: BEARINGS 4.1 List FOUR advantages of plain bearings. (4) 4.2 Name THREE tools that may be used to remove anti-friction bearing. (3) [7] QUESTION 5: LUBRICATION AND VALVES 5.1 Name TWO types of shut-off valves. (2) 5.2 Differentiate between a normally open and a normally closed valve. (2) 5.3 Name the FOUR different types of lubricators shown in FIGURE 1 below.

Write only the answer next to the question number (5.3.1–5.3.4). in the ANSWER BOOK.

5.3.1 5.3.2 5.3.3 5.3.4

FIGURE 1 (4 x 1)

(4) [8] QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND WATER-PIPE SYSTEMS 6.1 Name any FOUR types of sealing materials used in pipeline installations. (4) 6.2 State THREE reasons for the lagging (insulating) of steam-pipelines. (3) [7] QUESTION 7: PUMPS 7.1 Name the THREE categories into which pumps are classified. (3) 7.2 Briefly explain the operation of a centrifugal pump. (3) [6]

(11022032) -5- T640(E)(M30)T


QUESTION 8: COMPRESSORS Name the FIVE compressor components labelled 8.1 – 8.5 in FIGURE 2 below. Write only the name of the component next to the question number (8.1–8.5) in the ANSWER BOOK.

FIGURE 2

[5] QUESTION 9: V-BELT, CHAIN, GEAR DRIVES AND REDUCTION GEARBOXES 9.1 Explain the following terms relating to chain drives: 9.1.1 Chain pitch 9.1.2 Drive sprocket (2 x 1) (2) 9.2 State TWO reasons for the use of a guard on chain drives. (2) 9.3 State THREE precautions to be taken when working on V-belt drives. (3) 9.4 List THREE advantages of gear drives over belt and chain drives. (3) [10]

TOTAL SECTION A: 60

8.1

8.2 8.5

8.4

8.3

(11022032) -6- T640(E)(M30)T


SECTION B Answer only TWO of the questions in this section. QUESTION 10: HYDRAULICS AND PNEUMATICS 10.1 Name the components (10.1.1–10.1.5) associated with the ISO symbols in

FIGURE 3 below. Write only the name of the component next to the question number (10.1.1–10.1.5) in the ANSWER BOOK.

FIGURE 3

(5) 10.2 Describe the main difference between a pneumatic system and a hydraulic

system.

(2) 10.3 List the THREE ways by which directional control valves can be actuated. (3) 10.4 State the function of the following hydraulic components: 10.4.1 Hydraulic motor 10.4.2 Tank/Reservoir 10.4.3 Pressure-relief valve (3 x 1) (3) 10.5 List TWO functions of valves in a hydraulic system. (2) 10.6 Name the components associated with the ISO symbols in FIGURE 4 below.

Write only the name of the component next to the question number (10.6.1–10.6.5) in the ANSWER BOOK.

FIGURE 4

(5) [20]

10.6.4

10.6.2

10.6.5

10.6.3

10.6.1

(11022032) -7- T640(E)(M30)T


QUESTION 11: CENTRE LATHES 11.1 Briefly describe how the following lathe mandrels operate: 11.1.1 Sliding cone mandrel 11.1.2 Expanding mandrel (2 x 2) (4) 11.2 The compound slide is used for taper turning on a centre lathe. 11.2.1 State TWO advantages of the use of the compound slide 11.2.2 State TWO disadvantages of the use of the compound slide (2 x 2) (4) 11.3 State TWO methods of tailstock set-over, as applicable to taper-turning. (2) 11.4 Explain the main difference between the travelling steady and the fixed steady

used on centre lathes

(2) 11.5 A taper of 1 in 40 has to be turned on a workpiece 280 mm long. Calculate

the amount of tailstock set-over required.

(3) 11.6 A round shaft with an outside diameter of 45 mm must be provided with a two-

start thread with a 10 mm pitch. Calculate the helix angle of the thread (θ).

(5) [20] QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 Identify the milling cutter types shown in FIGURE 5 below. Write the answers

next to the question number (12.1.1–12.1.3) in the ANSWER BOOK.

FIGURE 5 (3) 12.2 Name any FOUR components of a dividing head. (4) 12.3 State THREE possible factors which cause the burning of the workpiece when

surface grinding.

(3)

Copyright reserved

12.4 Calculate the cutting speed of the cutter, in metres per minute, when using a

cutter of 40 mm in diameter at a speed of 302 revolutions per minute.

(3) 12.5 Climb milling is one of many milling processes. 12.5.1 Explain climb milling with the aid of a freehand drawing. (5) 12.5.2 State TWO advantages of climb milling. (2) [20]

TOTAL SECTION B: GRAND TOTAL:

40 100

(11022032) T640(E)(M30)T

Copyright reserved


FORMULA SHEET

tf = f T N

π D NS =

60

S = π D n

40

N

N

9

D - d length of workpieceSet-over =

2 length of taper

length of workpieceSet-over = Ratio

2

θ Xtan =

2 L

Leading angle = 90 - (Helix angle + clearance angle)

Foll

owing angle = 90 + (Helix angle - clearance angle)

Lead = No. of starts pitch

PitchMean diameter = OD -

2

Leadtan θ =

Mean circumference



APRIL EXAMINATION


30 MARCH 2016


MARKING GUIDELINE

MARKING GUIDELINE -2- T640(E)(M30)T FITTING AND MACHINING THEORY N2


SECTION A QUESTION 1: OCCUPATIONAL SAFETY 1.1 Must be strong and long lasting

Must not interfere with the operation of the machine

Must be easy to repair

Must be corrosion and fire resistant

Must provide maximum protection

Must not block access to other areas

Must block access to danger zones during operation

Must be free from hazards such as splinters and pinch points

Should be a permanent part of the machine

Effective operation of the machine should not be affected by the guard

(Any 5 x 1) [5] OR 1.2 1.2.1 Area to be sufficiently illuminated so that moving parts can be

clearly seen.

1.2.2 No light or lamp is allowed inside a mine unless the director

general of mines approves it.

1.2.3 Safety valves must be tested regularly to ensure opening at

authorised gauge pressure.

1.2.4 No cables to be placed or suspended in an unprotected manner.

They must be laid in such a way that damage is avoided.

1.2.5 No person is allowed to work in and un-illuminated part of a mine

unless they carry a light.

(5 x 1) [5] QUESTION 2: COUPLINGS

Easier to handle short shafts than long shafts

Easier to transport short shafts than long shafts

Maintenance is easier on short shafts than on long shafts

Cheaper to manufacture short shafts than long shafts

Manpower is reduced during maintenance

Shorts shafts do not bend as much as long shafts

(Any 5 x 1) [5]



QUESTION 3: LIMITS AND FITS 3.1 3.1.1 The hole basis system is used when a shaft is machined within

limits to fit a standard existing hole.

3.1.2 Minimum allowance is the smallest distance between the smallest hole size and the largest shaft size.

Minimum allowance is the smallest allowable distance between two mating components. (Any 1 x 1)

3.1.3 Bilateral tolerance is when the tolerance range is allowed on both sides of the basic size.

3.1.4 Transition fit is a fit in which the shaft may be slightly larger or smaller in diameter than the hole and still remain within limits.

(4 x 1) (4) 3.2 Minimum allowance = smallest hole size – largest shaft size = (30 - 0,015) – (30 - 0,025) = 0,01 mm (3) [7] QUESTION 4: BEARINGS 4.1 The operation is quiet

Low cost

Great rigidity

Can be replaced when worn

Life is not limited by fatigue Easy to manufacture (Any 4 x 1) (4) 4.2 Screw puller

Hydraulic puller

Puller plates

Impact puller

Hydraulic press

Bearing induction heater

Heated oil bath

Heating lamps

Wheel puller (Any 3 x 1) (3)

[7]



QUESTION 5: LUBRICATION AND VALVES 5.1 Ball valve

Gate valve

Globe valve

Diaphragm valve

(Any 2 x 1) (2) 5.2 Normally open valves are designed to be opened when in use whereas a

normally closed valve is closed during normal use

(2) 5.3 5.3.1 Stauffer grease lubricator 5.3.2 Wick-feed lubricator 5.3.3 Hand-operated grease pump 5.3.4 Grease gun (4 x 1) (4) [8] QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND WATER-PIPE SYSTEMS 6.1 Asbestos

Cotton

Nylon

Rubber

Neoprene

Teflon

Graphite

Aluminium

Babbit or white metal

Cork (Any 4 x 1)

(4)

6.2 Prevent heat loss as the pipeline carries steam or hot water from one place

to another.

To prevent condensation or water forming in a steam pipeline

To prevent water hammer in steam pipelines

For more accurate gauge readings

To prevent water entering the machine (Any 3 x 1)

(3) [7]



QUESTION 7: PUMPS 7.1 Centrifugal pump

Reciprocating pump

Rotary pump (3 x 1)

(3) 7.2 As water circulates inside the casing a vortex is created at the centre, which

causes a vacuum. This vacuum allows more water to be drawn into the casing. A centrifugal force causes the water at the outside circumference of the casing to be forced through the delivery outlet.

(3) [6]

QUESTION 8: COMPRESSORS 8.1 Lubricator 8.2 Sheave 8.3 Piston 8.4 Connecting rod 8.5 Cotter [5] QUESTION 9: V-BELT, CHAIN, GEAR DRIVES AND REDUCTION GEARBOXES 9.1 9.1.1 Chain pitch is the distance from the centre of one pin to the centre

of the next pin.

9.1.2 The drive sprocket is the sprocket that is attached to the motor

from which the driving motion is performed.

(2 x 1) (2) 9.2 Protect persons working in close proximity to a chain drive, in case of

chain breakage.

Protect machinery, in case of chain breakage.

Houses the lubrication system. (Any 2 x 1)

(2)

9.3 Always make sure that the V-belt drive has a guard around it

Make sure that the machine is switched off when replacing V-belts

Never adjust the slack of a V-belt while the machine is in motion

Use tensioning pulleys to adjust the slack of the belt

Use the correct size V-belt for the pulley and type of drive

Keep dirt and oil off the drive to prevent slip

Make sure that the pulleys are tightly fitted onto the shafts

Ensure that the pulleys are in line with each other

Always keep spare V-belts so that broken ones can be replaced immediately. (Any 3 x 1)

(3)


Copyright reserved

9.4 Unlike V-belt and chain drives, gear drives are positive drive, that is, no slip is possible

Gear drives can be used in confined spaces whereas V-belt and chain drives are used over longer distances

Gear drives can deal with higher torque than V-belt and chain drives

Gear drives are more durable than V-belt and chain drives (Any 3 x 1)

(3)

[10]

TOTAL SECTION A: 60



SECTION B Candidates must answer only TWO questions in this section. QUESTION 10: HYDRAULICS AND PNEUMATICS 10.1 10.1.1 Air dryer 10.1.2 Filter with manual drain 10.1.3 Filter with automatic drain 10.1.4 Filter or regulator 10.1.5 Single-acting cylinder with spring return (5 x 1) (5) 10.2 In hydraulic systems, oil is the working medium whereas in pneumatics

systems, air is the working medium.

In hydraulic systems, the excess oil is returned to the reservoir whereas in pneumatic systems, the excess air is exhausted to the atmosphere. (Any 1 x 2)

(2)

10.3 Manually

Electrically

By fluid pressure (pilot pressure) (3 x 1)

(3) 10.4 10.4.1 Hydraulic motor is a hydraulic source of rotary power, which drives

components

10.4.2 Tank/Reservoir is a storage container for hydraulic oil which is to

be used in the system and acts as return station.

10.4.3 Pressure-relief valve regulates the system pressure, keeping it at a

fixed pressure for end use.

(3 x 1) (3) 10.5 Controls energy flow

Opens or closes the path of flow

Directs the flow

Regulates the flow (Any 2 x 1)

(2)

10.6 10.6.1 Pump 10.6.2 Single-acting cylinder 10.6.3 Check valve 10.6.4 4/3 way directional control valve 10.6.5 Tank/Reservoir (5 x 1) (5) [20]



QUESTION 11: CENTRE LATHES 11.1 11.1.1 The fixed cone holds the work in position while the sliding cone

can be tightened onto the workpiece by means of a fastening nut on the back end.

11.1.2 A split tapered bush fits over a tapered shaft. By driving the shaft

into the bush, the bush opens up to accommodate workpieces of various hole sizes.

(2 x 2) (4) 11.2 11.2.1 Time saving

Concentricity is guaranteed

Simplicity of operation and calculations

Internal and external tapers can be turned

Short tapers can be turned to any angle (Any 2 x 1)

(2)

11.2.2 The length of the taper is limited to the length of the travel of the

compound slide.

No automatic feed, only by hand

Not very accurate angle (set by eye judgement) (Any 2 x 1)

(2)

11.3 The dial test indicator method

The graduated sleeve method

(2) 11.4 The travelling steady is fitted to the carriage of the lathe and travels along with

the tool whereas the fixed steady is clamped on the slideway of the lathe and does not move with the tool.

(2) 11.5 Lengthof workpiece

Tailstock set -over = × Ratio 2

280 1= ×

2 40

= 3,5 mm

(3)

11.6 Lead=No. of starts × Pitch = 2 × 10 = 20 mm

Pitch 10Mean diameter = OD - = 45 - = 40 mm

2 2

Lead 20tan θ = = = 0,159

Mean Circumference π ×40

-1 θ = tan 0,159 = 9,043°

(5)

[20]


Copyright reserved

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 12.1.1

12.1.2 12.1.3

Ball-nose cutter T-slot cutter Dove-tail cutter

(3 x 1) (3) 12.2 Rapid index plate

Index plate for simple indexing

Angular head with degrees on

Spindle

Crank handle

Single-start worm

Worm wheel

Sector arms (Any 4 x 1)

(4) 12.3 Too slow a speed

Metal clogging the space between abrasive particles/wheel clogged

Wrong wheel/wheel too hard

Insufficient coolant/disruption in coolant supply (Any 3 x 1)

(3)

12.4 S = D N

= 0,04 302

= 37,95 m/min

(3) 12.5 12.5.1

(for drawing) The teeth cuts from top to bottom. The direction of cutter and feed is in the same.

(5)

12.5.2 Deeper cuts can be taken

A finer finish is obtained

(2)

[20]


40 100

(11022032) T650(E)(A17)T


T650(E)(A17)T

APRIL EXAMINATION



(11022032)

17 April 2015 (Y-Paper) 13:00–16:00

Candidates will need drawing instruments.



(11022032) -2- T650(E)(A17)T







INSTRUCTIONS AND INFORMATION 1. 2. 3. 4. 5.

Answer ALL the questions in SECTION A. Note that there is a choice in QUESTION 1 where either QUESTION 1.1 OR 1.2 must be answered. Answer ONLY TWO questions from SECTION B. Read ALL the questions carefully. Number the answers according to the numbering system used in this question paper. Write neatly and legibly.

(11022032) -3- T650(E)(A17)T


SECTION A ANSWER ALL THE QUESTIONS IN SECTION A. NOTE THAT QUESTION 1 HAS A CHOICE.

QUESTION 1: OCCUPATIONAL SAFETY Answer QUESTION 1.1 or QUESTION 1.2 1.1 State FIVE characteristics of an effective machine guard. [5]

OR 1.2 State FIVE regulations associated with First Aid certification for underground

and surface mine workers

[5] QUESTION 2: COUPLINGS FIGURE 1 shows a sketch of a coupling.

FIGURE 1 2.1 Name the type of coupling shown in FIGURE 1. (1) 2.2 Describe the construction of this coupling.

(4) 2.3 Does this coupling fall in the group classification of fixed couplings? Indicate

by writing YES or NO and give a reason for your answer.

(2) [7]

(11022032) -4- T650(E)(A17)T


QUESTION 3: LIMITS AND FITS 3.1 FIGURE 2 below, shows an example of an interference fit between a bush

and shaft. Labels (A–D) represent various terms associated with limits. Identify these terms. Write down the answers next to the letters (A–D) in the ANSWER BOOK.

FIGURE 2 (4) 3.2 A shaft has to be machined according to a fit within the limits – 36 H7 - k6 in

order for the shaft to fit the hole. Use the information in TABLE 1 on page 5.

3.2.1 What type of limit system would apply in this case? (1) 3.2.2 What is the type of fit derived from this dimension? (1) 3.2.3 What is the tolerance of the shaft? (1) 3.2.4 Is this tolerance bi-lateral or unilateral? (1)

[8]

(11022032) T650(E)(A17)T


TABLE 1 OF TABLE OF LIMITS AND FITS / GRENSE EN PASSINGSTABEL

Clearance Fits / Vryloop Passings Transition Fits / Oorgangspassings Interference Fits/ Stuitpassings

H11

Holes/ Gate

H9 H9

H8 n6 p6 s6

H7 H7 H7 k6 H7 H7

0

h6

g6

f7

Shafts/ Asse

c11 e9

d10

Nominal sizes / Nominale mates

(mm)

Tolerance / Toleransie - units of 0.001 mm / Eenhede van 0.001 mm

Over To H11 c11 H9 d10 H9 e9 H8 f7 H7 g6 H7 h6 H7 k6 H7 n6 H7 p6 H7 s6

10 18 +110 -95 +43 -50 +43 -32 +27 -16 +8 -6 +18 -11 +18 +12 +18 +23 +18 +29 +18 +39

0 -205 0 -120 0 -75 0 -34 0 -17 0 -11 0 +1 0 +12 0 +18 0 +28

18 30 +130 -110 +52 -65 +52 -40 +33 -20 +221 -7 +21 -13 +21 +15 +21 +28 +21 +35 +21 +48

0 -240 0 -149 0 -92 0 -41 0 -20 0 0 0 +2 0 +15 0 +22 0 +35

30 40 +160 -120 +62 -80 +62 -50 +39 -25 +25 -9 +25 -16 +25 +18 +25 +33 +25 +42 +25 +59

0 -280 0 -180 0 -112 0 -50 0 -25 0 0 0 +2 0 +17 0 +26 0 +43

40 50 +190 -140 +74 -100 +74 -60 +46 -30 +30 -10 +30 -19 +30 +21 +30 +39 +30 +51 0 +53

0 -330 0 -220 0 -134 0 -60 0 -29 0 0 0 +2 0 +20 0 +32 +30 +78

50 65

+190 -150 +74 -100 +74 -60 +146 -30 +30 -10 +30 -19 +30 +21 +30 +39 +30 +51 0 +59

0

-340 0 -220 0 -134 0 -60 0 -29 0 0 0 +2 0 +20 0 +32 +35 +93

65 80

0 -390 +87 -20 +87 -72 +54 -36 +35 -12 +35 -22 +35 +25 +35 +45 +35 +59 0 +71

+220 -180 0 -260 0 -159 0 -71 0 -34 0 0 0 +3 0 +23 0 +37 +35 +101

0 -450 0 +92


-5-

(11022032) -6- T650(E)(A17)T


QUESTION 4: BEARINGS 4.1 Explain the function of a bearing. (2) 4.2 State one advantage of each of the following anti-friction bearings: 4.2.1 Spherical roller bearing (1) 4.2.2 Needle roller bearing (1) 4.3 Taper plain bearings are used to support rotating shafts or spindles. Shafts or

spindles in turn must be tapered and should have a threaded section with a threaded nut. What is the purpose of the threaded nut on the tapered shaft or spindle?

(1) [5]

QUESTION 5: LUBRICATION AND VALVES 5.1 Explain the meaning of the following lubrication terminology: 5.1.1 Cohesion (1) 5.1.2 Adhesion (1) 5.1.3 Viscosity (1) 5.2 State the TWO main functions of a valve. (2) 5.3 Explain the function of a foot-valve. (1)

[6] QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND WATER PIPE

SYSTEMS

6.1 Explain the function of a stuffing box. (2) 6.2 Name FOUR methods of joining plastic pipe used in water pipe systems. (4) 6.3 State THREE reasons for the failure of flanged joints. (3)

[9]

(11022032) -7- T650(E)(A17)T


QUESTION 7: PUMPS 7.1 State ONE function of a pump (2) 7.2 FIGURE 3 below shows a sketch of a pump.

FIGURE 3 7.2.1 Name the type of pump shown in FIGURE 3. (1) 7.2.2 Name the classification of this type of pump. (1) 7.2.3 Identify the THREE parts of the pump labelled (A–C) in FIGURE 3.

Write the answers next to the letters (A–C) in the ANSWER BOOK.

(3) [7]

QUESTION 8: COMPRESSORS Complete the following sentences/paragraph(s) by filling the missing word(s). Write only the word(s) next to the question number (8.1–8.5) in the ANSWER BOOK.

The (8.1…) stores air at high pressure until it is required for use. It is usually fitted with a/an (8.2…) for monitoring the air pressure. A/An (8.3…) is fitted to the air receiver, usually located at the (8.4…) point, to drain any water that may accumulate as a result of (8.5…)

[5] QUESTION 9: V-BELT, GEAR AND CHAIN DRIVES 9.1 Explain THREE factors to be considered when installing V-belts. (3) 9.2 State THREE applications of gear drives. (3) 9.3 State TWO safety precautions to be considered when working with or around

chain drives.

(2) [8]

TOTAL SECTION A: 60

(11022032) -8- T650(E)(A17)T


SECTION B

ANSWER ONLY TWO QUESTIONS IN SECTION B.

QUESTION 10: HYDRAULICS AND PNEUMATICS 10.1 Hydraulic systems consist of several components. 10.1.1 Name THREE of the basic components used in a hydraulic system. (3) 10.1.2 State ONE functions of each of the components that you have

named in QUESTION 10.1.1.

(3) 10.2 State TWO disadvantages of pneumatic systems. (2) 10.3 Identify the TWO control valves shown in FIGURE 4. Write only the answer

next to the question numbers (10.3.1 and 10.3.2) in the ANSWER BOOK.

10.3.1 10.3.2

(4)

FIGURE 4 10.4 FIGURE 5 shows part of a pneumatic circuit. Identify the parts labelled A and

B in FIGURE 5 below. Write only the answer next to the letters (A and B) in the ANSWER BOOK.

FIGURE 5 (2)

A

B

(11022032) -9- T650(E)(A17)T


10.5 Make a neat, simple, line sketch of a hydraulic power unit (power pack) in a

typical circuit diagram. Clearly show the symbols representing the following hydraulic components:

10.5.1 Pump (1) 10.5.2 Electric motor (1) 10.5.3 Pressure relief valve (1) 10.5.4 Check valve (1) 10.5.5 Reservoir (1) 10.5.6 Filter (1)

[20] QUESTION 11: CENTRE LATHES 11.1 Name THREE advantages of the use of the taper turning attachment method

when taper-turning on a lathe.

(3) 11.2 A spindle is to be turned to the dimensions given in FIGURE 6 below.

FIGURE 6 11.2.1 Calculate the amount of tailstock set-over. (2) 11.2.2 Calculate the included angle of the tapered portion. Write the

answer in degrees and minutes.

(3) 11.3 A carbon steel pin is to receive a finishing cut on a centre lathe. The cutting

speed for carbon steel is 56,55 m/min. Calculate the diameter of the carbon steel pin if the spindle speed setting is 1 800 r/min.

(3)

11.4 A work piece is to be machined on a centre lathe. The length of one cut on the work piece is 250 mm. The lathe feed is set at 0,5 mm/rev. The spindle speed is 199 r/min. Calculate the time taken, in minutes and seconds, to make one longitudinal cut on the work piece.

(3)

250

150

Ø3

0

Ø4

5

(11022032) -10- T650(E)(A17)T


11.5

A two-start square thread of 12 mm pitch has to be machined on a round shaft with an outside diameter of 66 mm. Take the clearance angle as 3°. Calculate:

11.5.1 The helix angle (θ) of the thread (3)

11.5.2 The lead angle of the cutting tool (1)

11.5.3 The following angle of the cutting tool (1)

11.5.4 The axial distance a nut would travel after screwing it on this thread for ONE revolution

(1)

[20]

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 Name FOUR advantages for using milling cutters with coarse teeth. (4)

12.2 Use a Browne and Sharpe index plate, as shown below, to calculate the indexing required for the following:

12.2.1 58 equally spaced gear teeth (3)

12.2.2 An angular-shaped groove of 45° (3)

The Browne and Sharpe Dividing Head

Plate 1 15 16 17 18 19 20

Plate 2 21 23 27 29 31 33

Plate 3 37 39 41 43 47 49

12.3 Describe the following types of grinding terms:

12.3.1 Off-hand grinding (1)

12.3.2 Precision grinding (1)

12.4 A 90 mm milling cutter with 14 teeth operates at a cutting speed of 25 m/min. The feed per tooth is 0,08. Calculate the feed in mm/min.

(5)

12.5 Give THREE reasons for chatter marks on a completed surface-ground work-piece.

(3) [20]


40 100

(11022032) -11- T650(E)(A17)T



FORMULA SHEET

f = ft × T × N

L = f × N × t

S = 60

DN

S = DN

N

40

9

N

Set-over = taper of length

workpieceof length

2

dD

tan L

X

2

Leading angle = 90° – (Helix angle + clearance angle)

Folowing angle = 90° + (Helix angle – clearance angle)

Lead = No of starts × pitch



APRIL EXAMINATION


17 APRIL 2015


√ = ½ mark = 1 mark

MARKING GUIDELINE

MARKING GUIDELINE -2- T630(E)(A17)T FITTING AND MACHINING THEORY N2


SECTION A: ALL QUESTIONS ARE TO BE MARKED IN THIS SECTION. QUESTION 1: OCCUPATIONAL SAFETY NOTE: Candidates need ONLY answer QUESTION 1.1 or QUESTION 1.2. 1.1 Provide maximum positive protection.

Blocks access to danger zones during operations.

Must be corrosion and fire resistant

Easily repairable

Must be free from hazards such as splinters and pinch points

It should be a permanent part of the machine

Efficient operation of the machine should not be affected by the guard (Any 5 x 1)

[5]

OR

1.2 Underground – Every person in charge of more than 300 workmen must

be in possession of a first aid certificate.

Underground – All workers under the age of 50 must have a first aid certificate

Surface – All workers near machinery on the surface must be in possession of a first aid certificate

Every person has a period of one year within which to obtain a first aid certificate

First aid certificates are renewable every three years

[5]

QUESTION 2: COUPLINGS

2.1 Gear coupling (1)

2.2 Each of the two shafts has a sleeve keyed to it. The sleeves have gear teeth on the outer rim. The two sleeves are coupled together by two half couplings with internal gear teeth. The half couplings have flanges which are bolted together.

(4)

2.3 Yes. It does not allow for much misalignment of shafts. (2) [7]

QUESTION 3: LIMITS AND FITS

3.1 A Tolerance B Minimum allowance C Low limit of shaft size D Upper/high limit of shaft size

(4 × 1)

(4)



3.2 3.2.1 Hole basis 3.2.2 Transition fit 3.2.3 0,018

0,00236

3.2.4 Unilateral tolerance (4 × 1)

(4) [8]

QUESTION 4: BEARINGS

4.1 A bearing allows for relative motion between machine components at high speed and under high loading conditions.

A bearing is a device designed to cut down the friction between two machine components

(Any 1 x 2)

(2)

4.2 4.2.1 They are able to accommodate errors of alignment

They can carry very heavy radial and axial loads (Any 1 × 1)

(1)

4.2.2 Overall diameter is very small and can be used in areas where

space is limited

(1)

4.3 The threaded nut on the tapered shaft or spindle is used to take up wear of the bearing by lightly tightening the nut.

(1) [5]

QUESTION 5: LUBRICATION AND VALVES 5.1 5.1.1 Cohesion is the force that holds a substance together, e.g.

grease is more cohesive than oil.

(1) 5.1.2 Adhesion is the ability of a substance to cling to another material,

e.g. oil cling to steel more than water.

(1) 5.1.3 Viscosity is the resistance of flow of a liquid. (1) 5.2 To control the pressure in a liquid

To control direction of flow of a liquid

(2) 5.3 Acts like a non-return valve, preventing water from flowing back into the

sump/reservoir/tank every time the pump is stopped.

The valve allows flow of fluid in one direction only. (Any 1 x 1)

(1) [6]



QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND WATER PIPE

SYSTEMS

6.1 To prevent gas or liquid in a cylinder from escaping past the piston rod. (2) 6.2 Socket fusion

Butt-and-strap joint

Compression jointing for plastic piping

O-ring seals for push fit waste pipes

Fillet welding

Screwed (threaded)

Flanged (Any 4 x 1)

(4) 6.3 The fitting between the flanges is not perfect

Bolts and nuts keeping the flanges together are not properly tightened

The sealing material is damaged

Flanges are cracked or corroded

Poor surface finish on the flanges

Misalignment of flanges

Joints gets damaged due to vibration, expansion or contraction (Any 3 x 1)

(3) [9]

QUESTION 7: PUMPS 7.1 A pump is a mechanical device used to raise a fluid from a lower to a

higher level .

(2)

7.2 7.2.1 Flexible impeller pump (1) 7.2.2 Rotary pump classification (1) 7.2.3

A – Outlet B – Inlet C – Impeller or flexible vane

(3) [7]

QUESTION 8: COMPRESSORS 8.1 Air receiver 8.2 Pressure gauge 8.3 Drain valve 8.4 Lowest 8.5 Moisture / condensation / water

(5 × 1)

[5]



QUESTION 9: V-BELT, GEAR AND CHAIN DRIVES 9.1 The drive and driven pulleys must be correctly aligned to avoid premature

excessive wear.

Take-up allowance – to effectively fit the belt over the two pulleys, the distance between the pulleys must be decreased by loosening the motor mounting bolts and moving the motor closer to the driven pulley.

The belt tension must be correctly adjusted.

(3)

9.2 To transmit high power

To increase or decrease the speed

To increase or decrease the torque

The change the direction of a drive

To be used where space is limited (Any 3 x 1)

(3) 9.3 Do not repair a chain drive while the machine is in motion

Never use a new chain on worn out sprockets

Make sure that the chain drive is lubricated at all times

Check chain elongation and replace links to take up the slack

Covers must be fitted around chain drives

Ensure that shafts and sprockets are aligned to prevent damage (Any 2 x 1)

(2) [8]

TOTAL SECTION A: 60



SECTION B: ONLY TWO OF THE QUESTIONS IN SECTION B NEED TO BE ANSWERED.

QUESTION 10: HYDRAULICS AND PNEUMATICS

10.1 10.1.1 Pump

Reservoir

Actuator

Valves or pressure relief valve or control valve

Piping (Any 3 x 1)

(3)

10.1.2 Pump – produces the movement of hydraulic fluid which is necessary to develop pressure in the fluid

Reservoir – is a storage for hydraulic fluid until it is needed for the operation of the system

Actuator – change the hydraulic pressure into mechanical movement

Valves – used to control the flow of hydraulic fluid in the system

Piping – channels the pressurised hydraulic fluid from the reservoir to actuators

(Any 3 × 1)

(3)

10.2 Power losses occur over long distances

Separates air from oil

Dissipates heat

Supports motor/pump (Any 2 × 1)

(2)

10.3 10.3.1 2/2 way directional control valve (1)

10.3.2 3/2 way directional control valve (1)

10.4 10.4.1 Air receiver (1)

10.4.2 Actuator (1) 10.5

(6)

10.5.1

10.5.5

10.5.4 10.5.3

10.5.2

10.5.6



10.6 10.6.1 Protects the system from excessive pressure (1)

10.6.2 Controls the direction of flow of air (1) [20]

QUESTION 11: CENTRE LATHES 11.1 Auto-feed

Time-saving

Guaranteed smooth finish

Easy to set-up

Long tapers can be turned

External and internal tapers are possible

Large quantities of the same tapers can be turned (Any 3 × 1)

(3)

11.2 11.2.1

2

45 30 250

2 150

12,5

D d lengthof workpieceSet over

lengthof taper

mm

(2)

11.2.2

1

tan2

7,5tan

2 150

tan 0,052

2,862

5,72

5 43'

x

L

(3)

11.3

56,55

1800

10

S DN

SD

N

mm

(3)

√ √

√

√

√

√

√

√

√

√



11.4

250

0,5 199

2 30,7

L f N t

Lt

f N

minutes seconds

(3)

11.5 11.5.1 .

2 12

24

Lead No of starts Pitch

mm

1

2

166 12

2

60

Pitchdiameter OD Pitch

mm

tan

24

60

0,127

Lead

Pitchcircumference

1tan 0,127

7,25

(3)

11.5.2

90

90 7, 256 3

79,744

Leading angle helix angle clearanceangle

mm

(1)

11.5.3

90

90 7,256 3

94,256

Following angle helix angle clearanceangle

mm

(1)

11.5.4 12mm (1)

[20]

√

√

√

√

√

√

√

√

√

√

√



QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 Power consumption is reduced

Chattering is reduced

Much better cutting action

Sharpening/grinding is made easy

(4)

12.2 12.2.1 40

40=

58

20

29

2 20 29

N

UsePlate holes ona holecircle

(3)

12.2.2

9

45=

9

5

5

N

full turns of the crank handle

(3)

12.3 12.3.1 This is done on a bench or pedestal grinder and the work-piece is usually held in the hands.

(1)

12.3.2 This is used to finish hardened parts to accurate sizes of micro-tolerances.

(1)

12.4

25

0,09

88,42 /

S DN

SN

N

r min

0,08 14 88,42

99 /

tf f T N

m min

(5) 12.5 Machine vibration

Wheel spindle vibration

Out-of-balance wheel

Machine not securely mounted (Any 3 × 1)

(3)

[20] TOTAL SECTION B:

GRAND TOTAL: 60

100

√

√


T630(E)(N12)T




(11022032)

12 November 2014 (Y-Paper) 13:00–16:00



(11022032) -2- T630(E)(N12)T






required number of questions will be marked. All work you do not want to be marked, must be clearly crossed out.

INSTRUCTIONS AND INFORMATION 1. 2. 3. 4. 5.

Answer either QUESTION 1.1 or QUESTION 1.2 and ALL other questions in SECTION A. Answer only TWO questions from SECTION B. Read ALL the questions carefully. Number the answers according to the numbering system used in this question paper. Write neatly and legibly.

(11022032) -3- T630(E)(N12)T


SECTION A QUESTION 1: OCCUPATIONAL SAFETY Answer either QUESTION 1.1 or QUESTION 1.2. 1.1 State FIVE rules for the safe handling and storage of compressed gas

cylinders.

[5]

OR

1.2 State FIVE precautions to be taken with regard to fire prevention in mines, according to the Minerals Act.

[5]

QUESTION 2: COUPLINGS FIGURE 1 below, shows a sketch of a coupling.

FIGURE 1 2.1 Name the type of coupling shown in FIGURE 1. (1) 2.2 Describe the conditions under which this coupling may be used. (2) 2.3 Does this coupling fall in the group classification of fixed couplings? Write only

'yes' or 'no' and give a reason for your answer.

(2) [5]

(11022032) -4- T630(E)(N12)T


QUESTION 3: LIMITS AND FITS 3.1 FIGURE 2 below, shows an example of a clearance fit between a bush and

shaft. Labels (A–D) represent various terms associated with limits. Identify these terms. Write down the answers next to the letters (A–D) in the ANSWER BOOK.

FIGURE 2 (4 × 1) (4) 3.2 A precision running fit between shaft and a sliding bearing is given as:

105H7- g6

What is meant by the following symbols represented by this fit? Write only the answer next to the question number (3.2.1–3.2.4) in the ANSWER BOOK.

3.2.1 The capital letter H 3.2.2 The number 7 3.2.3 The small letter g

3.2.4 The number 6

(4 × 1)

(4) [8]

QUESTION 4: BEARINGS 4.1 List FOUR properties of the materials used for plain bearings. (4) 4.2 Give FOUR reasons for the failure of anti-friction bearings. (4)

[8] QUESTION 5: LUBRICATION AND VALVES 5.1 State FIVE factors which must be considered when choosing a lubricant. (5) 5.2 Explain the working principles of a ball valve. (3)

[8]

(11022032) -5- T630(E)(N12)T


QUESTION 6: PACKING, STUFFING BOXES AND JOINTS AND PIPE SYSTEMS 6.1 State FIVE important guidelines to ensure the proper fitting of O-rings and

seals in hydraulic systems, in order to prevent premature failure.

(5)

6.2 Name FOUR common methods of joining steel water pipes. (4) [9]

QUESTION 7: PUMPS 7.1 Explain the function of a pump. (1)

7.2 FIGURE 3, below, shows a sketch of a gear pump where M represents the attachment to the pump motor.

Identify the parts labelled (A–D). Write the answer next the letters (A–D) in the ANSWER BOOK.

FIGURE 3 (4) [5]

QUESTION 8: COMPRESSORS Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (8.1–8.7) in the ANSWER BOOK.

8.1 Pneumatic tools are tools driven by liquid pressure.

8.2 Moisture traps are used on intercoolers and aftercoolers.

8.3 The low pressure cylinder is the second stage at which air is drawn in from the high pressure cylinder before being compressed, cooled and stored.

8.4 The device used to separate moisture from the air to prevent the presence of water in tools and machinery during pneumatic operation, is called the aftercooler.

A

C

B

D M

. .

.

. .

(11022032) -6- T630(E)(N12)T


8.5 Pistons and piston-rings are used in reciprocating compressors. 8.6 Start and stop control is operated on a compressor by a thermostat. 8.7 The air receiver is used for storing compressed air under high pressure until it

is ready for use. (7 × 1)

[7]

QUESTION 9: V-BELT, GEAR AND CHAIN DRIVES 9.1 Explain the principles of the following concepts with regards to gear drives: 9.1.1 Velocity ratio (1)

9.1.2 Mechanical advantage (1)

9.2 State THREE advantages that V-belt drives have over chain drives. (3)

[5] TOTAL SECTION A: 60

(11022032) -7- T630(E)(N12)T


SECTION B Answer only TWO questions from this section. QUESTION 10: PNEUMATICS AND HYDRAULICS 10.1 Give the TWO scientific factors responsible for the force and speed in the

actuator within a pneumatic system.

(2) 10.2 FIGURE 4 shows a hydraulic circuit.

Identify the parts labelled (A–D). Write the answer next the letters (A–D) in the ANSWER BOOK.

FIGURE 4 (4) 10.3 State THREE main functions of oil in a hydraulic flow system. (3) 10.4 State TWO functions of the reservoir. (2) 10.5 Answer the following questions based on the valve as shown in FIGURE 5

below.

FIGURE 5 10.5.1 How many ports are indicated in FIGURE 5 above?

(11022032) -8- T630(E)(N12)T


10.5.2 How many switching positions are indicated? 10.5.3 Is this valve normally open or normally closed? 10.5.4 What is the name of this valve?

(4 × 1)

(4) 10.6 Make neat freehand sketches of the symbols representing the following

pneumatic components:

10.6.1 Pressure source 10.6.2 Compressor 10.6.3 Air receiver 10.6.4 Pneumatic motor (half-rotation) 10.6.5 Dryer (5 × 1) (5)

[20] QUESTION 11: CENTRE LATHE 11.1 Name the THREE basic instructional forms applicable to a CNC lathe. (3) 11.2 A spindle with a taper of 1 in 14 is to be turned to the dimensions given in

FIGURE 6 below.

FIGURE 6 11.2.1 Calculate the amount of tailstock set-over. (2) 11.2.2

Calculate the included angle of the tapered portion in degrees and minutes.

(3)

11.3 A carbon steel pin with a diameter of 10 mm is to receive a finishing cut on a

centre lathe. The cutting speed for carbon steel is 56,55 m/min. Calculate the speed, in revolutions per minute, that you would set as the lathe’s rotational speed.

(3)

(11022032) -9- T630(E)(N12)T


11.4 Steadies are important accessories to a centre lathe. 11.4.1 State TWO uses of lathe steadies (2) 11.4.2 Name the steady, which is mounted to the lathe-bed. (1) 11.4.3 Name the steady, which is mounted to the lathe-saddle. (1) 11.5 A two-start square thread of 10 mm pitch, has to be machined on a round

shaft with an outside diameter of 70 mm. Assume the clearance angle to be 3°. Calculate the following:

11.5.1 The helix angle (θ) of the thread (3) 11.5.2 The lead angle of the cutting tool (1) 11.5.3 The following angle of the cutting tool (1)

[20]

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 Name the THREE types of indexing as performed on a milling machine. (3) 12.2 A work piece must have 13 gear-teeth machined on its circumference. 12.2.1 What type of indexing would you perform on this gearblank? (1) 12.2.2 Give a reason for the answer in QUESTION 12.2.1. (2) 12.2.3 Calculate the required indexing, using a Cincinnati dividing head as

shown in the TABLE below.

The Cincinnati dividing head

Side 1 24 25 28 30 34 37 38 39 41 42 43

Side 2 46 47 49 51 53 54 57 58 59 62 66

TABLE (3) 12.3 Grinding wheels have markings for identification purposes.

List FIVE factors by which you would identify a grinding wheel.

(5)

12.4 State FOUR advantages of using milling cutters with coarse teeth. (4) 12.5 Name TWO types of milling processes. (2)

[20] TOTAL SECTION B:

GRAND TOTAL: 40

100

(11022032) -10- T630(E)(N12)T



FORMULA SHEET

f = ft × T × N

S = 60

DN

S = DN

N

40

9

N

Set-over = taper of length

workpieceof length

2

dD

tan L

X

2

Leading angle = 90° – (Helix angle + clearance angle)

Folowing angle = 90° + (Helix angle – clearance angle)






12 NOVEMBER 2014

This marking guideline consists of 9 pages. √ = ½ mark = 1 mark

MARKING GUIDELINE



SECTION A QUESTION 1 1.1 Do not allow cylinders to slide or come into contact with sharp edges.

They may be rolled but not dragged.

Do not drop cylinders or allow them to come into violent contact with each other or with other hard objects.

Never load or offload cylinders by mean of electromagnetic cranes or chain-slings. A cage or lifting basket, made especially for the task, should be used.

Do not tamper with the safety devices found on the valves.

Do not use cylinders as roller beds for moving heavy articles.

Use a special cylinder trolley or hand truck, where possible.

Mark empty cylinders by using chalk or other marking material to distinguish between them and others which are full.

Always handle cylinders as if they are full.

Remove pressure regulators and equipment and replace valve guards before transporting cylinders.

Use warm, not boiling water, to free frozen valves as the fusible plug on acetylene cylinders melts at boiling point.

(Any 5 × 1)

[5]

OR

1.2 No person should leave any naked light or flame on or near any

combustible material or inflammable substance.

No combustible waste material must be stored in the vicinity of any installed electrical appliance or heating apparatus.

No welding, flame-cutting or flame heating must take place unless fire extinguishers have been provided.

No person is allowed to smoke or carry an open light in any cage, skip or any other conveyance in any shaft.

Calcium carbide is not to be taken underground unless it is in a lamp or water-tight container approved by the manager.

All machinery must be constructed, installed, operated and maintained so as to prevent dangerous heating

(Any 5 × 1)

[5]

QUESTION 2 2.1 Universal coupling (1) 2.2 This coupling connects two shafts whose axes are at an angle, other than

180°, with each other.

(2) 2.3 No. It accommodates self alignment group. (2)

[5]



QUESTION 3 3.1 A – Low limit of shaft

B – Higher/Upper limit of shaft C – Lower limit of bush D – High/Upper Limit of bush (4 × 1)

(4)

3.2 3.2.1

3.2.2 3.2.3 3.2.4

H = tolerance of hole 7 = grade or degree of tolerance on hole g = tolerance of shaft 6 = grade or degree of tolerance on shaft (4 × 1)

(4) [8]

QUESTION 4 4.1 Load Capacity

Corrosion resistance

Thermal conductivity

Fatigue strength

Embedded ability

Compatibility

Conformability

Cost (Any 4 × 1)

(4)

4.2 Insufficient lubrication

Drying-up of grease

Oil-pollution

Insufficient bearing clearance

Flat on rolling element/s

Shaft out of roundness

Over-lubrication

Foaming oil

Rotating journal sleeve

Bearing slips on shaft

Incorrect assembly

Excessive bearing clearance (Any 4 × 1)

(4) [8]



QUESTION 5 5.1 Speed between moving parts

Operating temperature

Load on bearing

Cost of lubricant

Environment

Clearance between the two components (Any 5 × 1)

(5)

5.2 A ball valve consists of a ball with a hole through it. When the opening in

the ball coincides with that of the pipeline, the fluid will flow. If the handle is turned through 90° to the pipeline, no flow will take place.

(3) [8]

QUESTION 6 6.1 Clean all surfaces.

Ensure the correct seal is used.

Ensure no damage while installing seal.

Lubricate the seal before installing.

Use a protective sheath over a threaded section to protect the seal.

Always tighten up lightly in the beginning for squaring up the seal. (Any 5 × 1)

(5) 6.2 Screwed

Welded

Flanged

Bell and spigot

Butt and strap joint

Threaded union (Any 4 × 1)

(4) [9]

QUESTION 7 7.1 A pump is used to transfer fluids or liquids from one place to another.

OR A pump is used to move fluids or liquids from a low level to a higher level.

(1)

7.2 A – Inlet

B – Outlet C – Driven gear D – Driver gear (4 × 1)

(4) [5]



QUESTION 8 8.1 8.2 8.3 8.4 8.5 8.6 8.7

False True False True True False True

(7 × 1)

[7]

QUESTION 9 9.1.1 Velocity ratio is the relationship between the speeds of the drive gear to the

speed of the driven gear OR the number of teeth of the driven gear to the number of teeth on the drive gear.

(1) 9.1.2 Mechanical advantage is the resultant effect between two meshing gears and

can be obtained by varying the velocity ratio between them.

(1) 9.2 Slip will take place when overloaded whereas in chain drives the chain

may break.

No lubrication required in belt drives whereas chain drives require lubrication.

Requires little attention as compared to chain drives.

Cheaper maintenance than chain drives.

Not as costly as chain drives,

Can operate over longer distances. (Any 3 × 1)

(3) [5]

TOTAL SECTION A: 60



SECTION B QUESTION 10 10.1 Pressure

Volume

(2)

10.2 A – Regulator or safety valve

B – Filter C – Pump D – Tank or reservoir (4 × 1)

(4)

10.3 Transmits energy or power

Lubricates

Prevents corrosion

Removes dirt

Cools (Any 3 × 1)

(3)

10.4 Storage of hydraulic fluid

Dissipates heat generated in the system

Separates air from oil

Allows contaminants to settle to the bottom (Any 2 × 1)

(2)

10.5 10.5.1 3 10.5.2 2 10.5.3 Normally closed – return to tank 10.5.4 3/2 Directional control valve

(4 × 1)

(4) 10.6 10.6.1

10.6.2

10.6.4



10.6.4

10.6.5

(5 × 1)

(5) [20]

QUESTION 11 11.1 G – Commands

M – Commands

Positional data

(3)

11.2 11.2.1

2

280 1

2 14

10

lengthof workpieceSet over Ratio

mm

(2)

11.2.2

1

0,5tan

2 14

tan 0,03572

2,0452

4,09

4 5, 4 '

(3)

11.3

56,55

0,01

1800 / min

S DN

SN

D

rev

(3)

11.4 11.4.1 To support long and slender work-pieces between the lathe spindle and tail-stock.

To reduce unnecessary vibration or chatter, thus ensuring a better finish.

To support work-pieces against the pressure of heavy machining.

To maintain concentricity of long work-pieces while machining. (Any 2 × 1)

(2)

√ √

√

√

√

√



11.4.2 Travelling (1)

11.4.3 Fixed (1) 11.5 11.5.1 .

2 10

20


mm

1

2

170 10

2

65


mm

tan

20

65

0,0797

Lead

Pitchcircumference

1tan 0,0797

5,59

(3)

11.5.2 Leading angle = 90° – (helix angle + clearance angle)

= 90° – (5,59 + 3°) = 81,41°

(1)

11.5.3 Following angle = 90° – (helix angle + clearance angle)

= 90° + (5,59 – 3°) = 92,59°

(1) [20]

√

√

√

√

√

√

√

√

√

√



QUESTION 12 12.1 Rapid Indexing

Simple Indexing

Angular Indexing

Differential Indexing (Any 3 × 1)

(3)

12.2 12.2.1 Simple indexing (1) 12.2.2 The number of teeth is easily divisible into 40 with a remainder

divisible into one of the Cincinnati hole circles.

(2) 12.2.3

40 40 1 = 3

13 13

13

13

1 3 3

13 3 39

N

turns and of a turn

Required indexing = 3 turns of crank & 3 holes in a 39 hole circle

(3)

12.3 Abrasive type

Grade of wheel

Bonding material

Grain size

Structure

(5)

12.4 Less power consumption.

Easy to sharpen.

Cheaper to manufacture.

Chattering is reduced.

(4)

12.5 Gang

Straddle

Slab

Slotting

Up-cut

Down-cut

Gear-cutting

Spiral or Helical milling

End-milling (Any 2 x 1)

(2) [20]

TOTAL SECTION B:

GRAND TOTAL: 40

100

√

√


T630(E)(J22)T

AUGUST EXAMINATION



(11022032)

22 July 2014 (Y-Paper) 13:00–16:00



(11022032) -2- T630(E)(J22)T








Answer ALL the questions in SECTION A Answer ONLY TWO questions in SECTION B Answer either QUESTION 1.1 OR 1.2 of QUESTION 1 Read ALL the questions carefully. Number the answers according to the numbering system used in this question paper. Write neatly and legibly.

(11022032) -3- T630(E)(J22)T


SECTION A ANSWER ALL THE QUESTIONS IN SECTION A. QUESTION 1: OCCUPATIONAL SAFETY Answer QUESTION 1.1 or QUESTION 1.2 1.1 Indicate whether the following statements are TRUE or FALSE with regard to

safety in the workplace. Choose the answer and write only 'true' or 'false' next to the question number (1.1.1–1.1.5) in the ANSWER BOOK.

1.1.1 Overhead transmission belts must be provided with guards 1.1.2 When using a ladder, never secure the top part by means of a

rope.

1.1.3 Fixed guards only move with each operation of the machine. 1.1.4 The manufacturer's information on a pressure vessel includes the

date of export.

1.1.5 A machine must be stopped immediately, if it becomes a danger to

those working in the area. (5 x 1)

(5)

OR 1.2 Indicate whether the following statements are TRUE or FALSE with regard to

safety in the workplace. Choose the answer and write only 'true' or 'false' next to the question number (1.2.1–1.2.5) in the ANSWER BOOK.

1.2.1 After a heating task is performed in a mine, a competent person

must inspect the area to ensure there is no possibility of a fire breaking out.

1.2.2 Naked lights are allowed BUT may not be left close to flammable

material that may cause a fire or an explosion.

1.2.3 Smoking is ONLY allowed in the lifting cage. 1.2.4 No welding, flame-cutting or flame heating is to take place in a

mine, unless fire extinguishers have been provided.

1.2.5 Calcium carbide is not to be taken underground unless it is in a

water tight container approved by the manager. (5 x 1)

(5) [5]

(11022032) -4- T630(E)(J22)T


QUESTION 2: COUPLINGS 2.1 Name FIVE different types of RIGID couplings. (5) 2.2 Give TWO reasons why it is necessary to ensure the correct alignment of a

fixed coupling.

(2) [7]

QUESTION 3: LIMITS AND FITS A shaft is to be fitted into a bush. The sizes given for the bush and shaft are:

BUSH SHAFT

0,08

0,0345

mm 0,02

0,0045

mm

3.1 Determine the following: 3.1.1 The minimum allowance of the fitted parts 3.1.2 The maximum allowance of the fitted parts 3.1.3 The tolerance on the shaft 3.1.4 The tolerance of the hole (4 x 1) (4) 3.2 What is the classification of this type of fit?

(1)

[5] QUESTION 4: BEARINGS 4.1 State one property of each of the following bearing materials: 4.1.1 White metal 4.1.2 Cast iron 4.1.3 Bronze 4.1.4 Nylon 4.1.5 Teflon

(5 x 1)

(5) 4.2 Name the THREE types of rolling elements used in the manufacture of anti-

friction design.

(3) [8]

(11022032) -5- T630(E)(J22)T


QUESTION 5: LUBRICATION AND VALVES FIGURE 1 represents a method of lubrication.

5.1 Name this type of lubrication. (1) 5.2 Briefly describe this lubrication method. (4) 5.3 State TWO functions of valves in fluid power systems. (2) 5.4 Differentiate between a normally open and a normally closed valve.

(2)

[9] QUESTION 6: PACKING, STUFFING BOXES, JOINTS AND WATER PIPE SYSTEMS 6.1 FIGURE 2 shows FOUR types of joints that allow for expansion and

contraction in pipelines. Name these FOUR types of joints. Write only the answer next to the question number (6.1.1 – 6.1.4) in the ANSWER BOOK.

(4)

FIGURE 2 6.2 List FOUR important guidelines to ensure the proper fitting of o-rings and

seals in hydraulic systems.

(4) [8]

FIGURE 1

(11022032) -6- T630(E)(J22)T


QUESTION 7: PUMPS 7.1 State TWO methods of neutralising water hammer in plunger pumps. (2) 7.2 Refer to FIGURE 3 and describe the operation of a double-acting plunger

pump by inserting the correct letters for the various valves. Write only the answer next to the question number (7.2.1 – 7.2.4) in the ANSWER BOOK. Stroke 1: As the plunger moves upwards, water enters the chamber through the inlet valve (7.2.1), and delivers water past the outlet valve (7.2.2). Stroke 2 As the plunger moves downwards, the water enters the chamber through the inlet valve (7.2.3), and delivers it past the outlet valve (7.2.4).

(4 x 1)

(4) [6]

FIGURE 3 QUESTION 8: COMPRESSORS Explain the function of each of the following compressor components: 8.1 Filter 8.2 Drain Valve 8.3 Intercooler 8.4 After cooler 8.5 Pressure regulator switch

(5 x 1)

[5]

C

A

B

D

(11022032) -7- T630(E)(J22)T


QUESTION 9: V-BELT, CHAIN, GEAR DRIVES AND REDUCTION GEARBOXES 9.1 State TWO advantages of chain drives when compared to gear drives. (2) 9.2 State TWO reasons for the need to eliminate excessive sag on chain drives. (2) 9.3 Name THREE different types of sprockets associated with chain drives. (3)

[7] TOTAL SECTION A: 60 SECTION B ANSWER ONLY TWO OF THE QUESTIONS IN SECTION B QUESTION 10: PNEUMATICS AND HYDRAULICS 10.1 Explain the function of a pressure relief valve in a hydraulic system. (1) 10.2 State FIVE factors which influence the choice of pneumatics over hydraulics

for transmitting power to machines.

(5) 10.3 Identify the FIVE hydraulic components shown in FIGURE 4. Write only the

answer next to the question number (10.3.1 – 10.3.5) in the ANSWER BOOK.

(5)

FIGURE 4 10.4 State FIVE basic aspects of inspection in the routine maintenance of a

hydraulic circuit.

(5) 10.5 Name the FOUR components which make up a pneumatic service unit. (4)

[20] QUESTION 11: CENTRE LATHE 11.1 State FOUR advantages of the use of mandrels for the machinist. (4) 11.2 Name the TWO methods for setting over the tailstock in preparation for taper-

turning on the centre lathe.

(2) 11.3 A taper of included angle 6° (SIX DEGREES) has to be turned on a work-

piece 280 mm long. Calculate the amount of tailstock set-over required.

(3) 11.4 A round shaft with a pitch diameter of 100mm must be provided with a two-

start square thread with a 5 mm pitch. The clearance angle is 3º.

(11022032) -8- T630(E)(J22)T


Calculate:

11.4.1 the helix angle of the thread (3) 11.4.2 the leading angle of the cutting tool (1) 11.4.3 the following angle of the cutting tool (1) 11.5 Explain the following terms applicable to CNC machining 11.5.1 Incremental programming (1) 11.5.2 Absolute programming (1) 11.6 List FOUR items of information required by the parts programmer when

writing a CNC machining programme.

(4) [20]

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 Name the FOUR types of milling cutters shown in FIGURE 5. Write only the

answer next to the question number (12.1.1 – 12.1.4) in the ANSWER BOOK.

(4)

FIGURE 5 12.2 A work-piece must have 13 gear-teeth machined on its circumference. 12.2.1 What type of indexing would you perform on this gear blank? (1) 12.2.2 Calculate the required indexing, using a Cincinnati dividing head as

shown below

(11022032) -9- T630(E)(J22)T


The Cincinnati Dividing Head Side

1 24 25 28 30 34 37 38 39 41 42 43

Side 2

46 47 49 51 53 54 57 58 59 62 66

(4) 12.3 State TWO advantages of the down cut milling process (2) 12.4 State TWO disadvantages of the down cut milling process (2) 12.5 State FOUR factors related to the workpiece, which will help you to select the

correct grinding wheel.

(4) 12.6 Name THREE types of bonding materials which holds the abrasive particles

in grinding wheels together.

(3) [20]

TOTAL SECTION B:

GRAND TOTAL: 40

100

(11022032) -10- T630(E)(J22)T



FORMULA SHEET

f = ft × T × N

S = 60

DN

S = DN

N

40

9

N

Set- over = taper of length

workpieceof length

2

dD

tan L

X

2

Leading angle = 90° - (Helix angle + clearance angle)

Following angle =90° + (Helix angle - clearance angle)




AUGUST EXAMINATION


22 JULY 2014


√ = ½ mark = 1 mark

MARKING GUIDELINE

MARKING GUIDELINE -2- T630(E)(J22)T FITTING AND MACHINING THEORY N2


QUESTION 1: OCCUPATIONAL SAFETY 1.1 1.1.1 True 1.1.2 False 1.1.3 False 1.1.4 False 1.1.5 True

(5 x 1)

(5)

OR 1.2 1.2.1 True 1.2.2 False 1.2.3 False 1.2.4 True 1.2.5 True

(5 x 1)

(5) [5]

QUESTION 2: COUPLINGS 2.1 Flange

Gear

Marine

Chain

Fluid

(5)

2.2 Efficient operation of machinery

Cost savings of the maintenance materials

Lengthens the life-span of components

Minimize downtime and the need for overtime (Any 2 x 1)

(2) [7]



QUESTION 3: LIMITS AND FITS 3.1.1 0,01 mm 3.1.2 0,08 mm 3.1.3 0,02 mm 3.1.4 0,05 mm (4 x 1) (4) 3.2 Clearance fit

(1)

[5] QUESTION 4: BEARINGS 4.1 4.1.1 Embeddability

Compatibility (Any 1)

4.1.2 High load carrying ability 4.1.3 Embedability

Resistance to seizure Corrosion resistant (Any 1)

4.1.4 Low coefficient of friction

Heat resistant No lubrication required (Any 1)

4.1.5 Low coefficient of friction

Self-lubricating Corrosion resistant High operating temperatures (Any 1)

(5 x 1)

(5) 4.2 Ball

Roller

Spherical roller

Needle roller (Any 3 x 1)

(3) [8]

QUESTION 5: LUBRICATION AND VALVES 5.1 Oil ring lubrication or splash feed lubrication (1) 5.2 The ring is in rolling contact with the shaft and the lower part is dipped in

the oil. As the shaft rotates the oil is brought up by the ring and is distributed along the shaft. Gradually, the oil drips back into the sump due to gravity.

(4)



5.3 A valve is used to control the direction of flow.

A valve is used to control pressure.

(2)

5.4 Normally open valves are designed to be opened when in use whereas a

normally closed valve is closed during normal use.

(2) [9]

QUESTION 6: PACKING, STUFFING BOXES, JOINTS AND WATER PIPE SYSTEMS 6.1 6.1.1

6.1.2 6.1.3 6.1.4

Corrugated expansion Expansion U-Joint / Expansion bend Full Loop Horseshoe

(4) 6.2 Clean all surfaces thoroughly

Ensure no damage to the oil ring or the surfaces

Use the correct seal

Lubricate the seal before fitting

Protective sheath to be used when fitting a ring seal or o-ring over a sharp ridge or threaded section

Tighten up lightly ensuring that the ring seal fits squarely (Any 4 x 1)

(4) [8]

QUESTION 7: PUMPS 7.1 open and close valves gradually

use an air chamber in the delivery line

(2)

7.2 7.2.1

7.2.2 7.2.3 7.2.4

C B A D

(4) [6]

QUESTION 8: COMPRESSORS 8.1 Ensure the intake of clean air, free of dirt and other foreign matter. 8.2 Used for draining water or moisture, which accumulates inside the air

receiver.

8.3 Cools air between the low pressure and high pressure stages before entering

the high-pressure cylinder.

8.4 Cools air after the high-pressure stage of compression before being stored in

the air receiver.

8.5 Allows the compressor to be switched off electrically, after the prescribed

pressure has been reached. (5 x 1)

[5]



QUESTION 9: V-BELT, CHAIN, GEAR DRIVES AND REDUCTION GEARBOXES 9.1 Transmits motion over long distances

Transmits motion to more than one drive at a time

Easier to maintain

Relative cheap (Any 2 x 1)

(2)

9.2 Destructive to the chain (shorter life span)

Detrimental to smooth running (low efficiency)

Causes whipping and vibration (chain could come off the sprocket)

Could ruin the sprockets (cause unnecessary wear) (Any 2 x 1)

(2)

9.3 Solid sprocket

Solid sprocket with spokes

Split sprocket with spokes

(3) [7]

TOTAL SECTION A: 60 SECTION B QUESTION 10: PNEUMATICS AND HYDRAULICS 10.1 Ensures that the normal working pressure is not exceeded by relieving excess

fluid pressure in the tank.

(1) 10.2 Noise factor

Cost factor

Power to weight ratio required

Cleanliness factor

Speed factor

Rigidity factor (Any 5 x 1)

(5) 10.3 10.3.1 – 2/2 Way Directional Control Valve

10.3.2 - 4/3 Way Directional Control Valve 10.3.3 - 5/2 Way Directional Control Valve 10.3.4 - 3/2 Way Directional Control Valve 10.3.5 - 4/2 Way Directional Control Valve

(5) 10.4 Hose fittings and pipes are not loose

Hoses and fittings must seat correctly

Oil and air filters are clean

Hoses and pipings are clean prior to installation

Release system pressure to tool before disconnecting

All guards to be fitted

Before start check that persons are clear of danger (Any 5 x 1)

(5)



10.5 Lubricator

Water trap

Drain valve

Filter

Pressure regulator (Any 4 x 1)

(4) [20]

QUESTION 11: CENTRE LATHE 11.1 Setting up time is reduced

Concentricity is guaranteed

Batch production of large amounts is possible

Mandrels can be modified to suit a large range of work

Setting up can be delegated to unskilled operators (Any 4 x 1)

(4)

11.2 Graduated sleeve method

Dial test indicator method

(2)

11.3

tan 2

6tan

2

280 0,0524

14,67

X

L

X L

mm

(3)

11.4 11.4.1 .

2 5

10


mm

1

2

1100 5

2

97,5


mm

tan

10

97,5

0,033

Lead

Pitchcircumference

1tan 0.033

1,87

(3)

√

√

√

√

√

√



11.4.2 Leading angle = 90° – (Helix + clearance angle) = 90° – (1,87 + 3) = 85,13°

(1) 11.4.3 Following angle = 90° + (helix – clearance angle)

= 90° + (1,87° – 3°)

= 88,87°

(1)

11.5 11.5.1 Incremental – each tool movement refers to the previous/ last tool

position

(1) 11.5.2 Absolute – each tool movement refers to a fixed point or origin

(zero point)

(1) 11.6 Material type

Stock length

Information from a drawing

Operating sequence

Tooling required

Dwell time

Coolant application

Sizes according to dimensioning position

Cutting speed (Any 4 x 1)

(4) [20]

QUESTION 12: MILLING MACHINES AND SURFACE GRINDERS 12.1 12.1.1

12.1.2 12.1.3 12.1.4

Square milling T-Slot milling Ball milling cutter End milling cutter

(4) 12.2 12.2.1 Simple indexing (1)

12.2.2

40 40 1 = 3

13 13

13

13

1 3 3

13 3 39

N

turns and of a turn

Required indexing = 3 turns of crank & 3 holes in a 39 hole circle.

(4)

√ √

√

√



12.3 Deeper cuts can be made as the force of the cutter is downwards.

A finer finish is obtained

(2)

12.4 Vibration in the arbor is unavoidable

A finer feed is to be used

Material with hard scales could cause damage to the cutter teeth (Any 2 x 1)

(2) 12.5 Amount of material to be ground

Hardness of the material

Wet or dry grinding

Wheel speed

Surface area (Any 4 x 1)

(4)

12.6 V: Vitrified

B: Resinoin or synthetic R: Rubber bonding E: Shellac S: Silicates

(Any 3 x 1)

(3) [20]

TOTAL SECTION B:

GRAND TOTAL: 40

100

Documents

Email: [email protected] questions & machining ... · 11.7 One method of cutting a taper on a centre lathe is the compound slide method. 11.7.1 State ONE advantage of using