NATIONAL CERTIFICATE (VOCATIONAL)
NOVEMBER EXAMINATION
FITTING AND TURNING
NQF LEVEL 4
QUESTION 1
1.1
|
1.1.1
1.1.2
1.1.3
1.1.4
1.1.5
1.1.6
1.1.7
1.1.8
1.1.9
1.1.10
|
B
C
D
B
B
A
C
A
B
B
(10 × 1)
|
(10)
|
1.2
|
1.2.1
|
Minor repairs
Repairs that can be done online and take a short period to complete
Major repairs
Large scale repairs that take longer time to accomplish.
(2 × 1)
|
(2)
|
1.2.2
|
Any ONE of the following:
Minor repairs - replacing a v-belt on a belt drive.
- repacking the stuffing box.
- replacing gaskets, seals or O rings.
Major repairs - replacing bearings.
- replacing a burnt-out electric motor.
- replacing a worn-out drive shaft.
(2 × 1)
|
(2)
|
1.3
|
Standby units ensure that the plant continues to run during the breakdown
of primary equipment.
|
(2)
|
1.4
|
· Time is not lost in having to order spares
· Money is saved by the company
(2 × 1)
|
(2)
|
1.5
|
Any TWO of the following:
· The machines may be operated to safe standards
· Allows a good standard to be maintained in operational procedure of the
equipment and machines
· Allows for efficiency with the repair and maintenance of equipment and
machines
|
(2)
| |
[20]
|
QUESTION 2
2.1
|
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
2.1.6
2.1.7
2.1.8
2.1.9
2.1.10
|
False
True
False
False
True
True
True
False
False
True
(10 × 1)
|
(10)
|
2.2
|
2.2.1
|
· Lubricator
· Pressure reducing valve
· Filter with water trap
|
(3)
|
2.2.2
|
Lubricator:
Provides oil to the compressed air to lubricate machine parts.
Pressure reducing valve:
Regulates the pressure of incoming compressed air.
Filter with water trap
Prevents dirt from entering machine and it drains water from
compressed air. (3 × 1)
|
(3)
|
2.3
|
Hydraulic fluid under pressure can have sufficient force to penetrate
the skin, causing serious injury or it may also cause damage to equipment.
|
(2)
|
2.4
|
2.4.1
|
Installation costs
Pneumatic systems are much cheaper to install than hydraulic systems.
|
2.4.2
|
Medium used
Pneumatic systems use compressed air while hydraulic systems use
pressurised oil/fluid.
(2 x 1)
|
(2)
| ||
[20]
|
QUESTION 3
3.1
|
3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3.1.6
3.1.7
3.1.8
3.1.9
3.1.10
|
D
F
E
G
H
A
B
I
J
C
(10 × 1)
|
(10)
|
3.2
|
3.2.1
|
The lathe is cutting the shaft at a taper, which means the headstock and
the tailstock are out of alignment.
|
(2)
|
3.2.2
|
Check the alignment of the headstock and the tailstock and reset accordingly.
|
(2)
|
3.3
|
S = p ´ D ´N
N = S
p ´ D
N = 25
 p´ 0,04
N = 198,94 r/minÖ
|
(1)
|
Also: L = f ´ N ´ t
t = L
f ´ N
t = 250 mm
0,5 ´ 198,94 Ö
t = 2,513 minutesÖ
|
(2)
|
3.4
|
The chuck key can be thrown out with great force and could kill or injure
the operator or someone else in the workshop.
|
(1)
|
3.5
|
· Poorly adjusted sideways
· Spindle speed too fast
· Feed rate too slow
· Incorrect tool height
· Worn spindle bearings.
(Any 2 × 1)
|
(2)
| ||
[20]
| ||||
QUESTION 4
4.1
|
4.1.1
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6
4.1.7
4.1.8
4.1.9
4.1.10
|
table
arbour
slot
slitting/slotting
convex
diameter (D)
machine
glasses/goggles
t-slot
differential
(10 × 1)
|
(10)
|
4.2
|
· The spindle speed
· The number of teeth on the cutter
· The feed per tooth of the cutter
· The material to be machined
· The type of cutter
· Quality of the finish required
· Size and rigidity of the workpiece (Any 3 × 1)
|
(3)
|
4.3
|
· The shape and size of the workpiece
· The force exerted by the cutter
· The distortion which may be caused by the clamping
· The allowable clamping pressure (Any 3 × 1)
|
(3)
|
4.4
|
√= 1 mark
INDEXING = 0/9
= 55/9
= 6 1/9 √
i.e. 6 full turns of crank handle and 1-hole on a 9 hole circle
Find number of holes on whole circle:
= 1/9 x 6/6
= 6/54
Answer: 6 full turns of crank handle and 6 holes in a 54-hole circle.√
|
(2)
|
4.5
|
· Rotational speed of cutter too high
· Feed rate of table too great.
· Cutter blunt
· Wrong grade of cutter used.
· Material too hard
· Insufficient coolant
· Lack of coolant (Any 2 × 1)
|
(2)
| |
[20]
|
QUESTION 5
5.1
|
Truing
Corrects the out-of-round condition of a grinding wheel.
Dressing
Restores the sharpness of the grinding wheel’s face.
or
Improves or alters the grinding wheel’s cutting action. (2 × 1)
|
(2)
|
5.2
|
· The material to be ground and its hardness
· The amount of material to be removed
· The grinding wheel speed
· The area of grinding contact
· The severity of the grinding operation
· The finish required
· Whether the grinding is to be wet or dry. (Any 3 × 1)
|
(3)
|
5.3
|
5.3.1
|
Burning of the work piece
|
(1)
|
5.3.2
|
· The grinding wheel is too hard
· Not enough coolant/coolant supply has been disrupted
· The grinding wheel is loaded/clogged (Any 2 x 1)
|
(2)
|
5.3.3
|
· Softer wheel should be used
· Increase the table feed
· Dress wheel more frequently
· Take lighter cuts (Any 1 x 1)
|
(2)
[10]
|
QUESTION 6
6.1
|
Computerised Numerical Control
|
(2)
|
6.2
|
· tool breakage
· Optimise cutting conditions
· Prolong life of expensive hardware
· Allow for increased workshop safety (Any 2 x 1)
|
(2)
|
6.3
|
Incremental dimensioning
The distance from one point to another is made with reference to the
last tool position.
Absolute dimensioning
All points are taken from a common reference point.
|
(2)
|
6.4
|
Specialised machines have their own specific dangers and risks.
|
(1)
|
6.5
|
√ = 1 MARKS
√ √ √
N 10 G90 X60.0 Y170.0 Z70.0
|
(3) [10]
|
TOTAL:
|
100
|
