MARKING GUIDELINES

QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC)
1.1 B (1)
1.2 A (1)
1.3 D (1)
1.4 A / C (1)
1.5 A (1)
1.6 C (1)  [6] 

QUESTION 2: SAFETY (GENERIC)
2.1 First-aid applications to an open wound:

• Use surgical gloves.
• Do not remove anything that is stuck to the wound.
• Never use sticky plaster on the wound.
• Cover the wound with a clean, lint-free cloth.
• Avoid using any oily substances or lotions on wounds.
• If necessary, cool wounds with cold water.
• Apply pressure to prevent blood loss if necessary.
• Avoid contact with blood from patient.
• If the wound is on your arm, raise the arm above your head to stop the bleeding.
  (Any 2 x 1) (2)

2.2 Surface grinder: (Already switched on)

• Never leave the grinder unattended.
• Switch off the machine when leaving.
• Don’t try to stop revolving emery wheel with your hand.
• Don’t adjust the machine while working.
• Don’t open any guard while the machine is on.
• Do not force the grinding wheel on to the work piece.
• Approach the work piece slowly and evenly.
• Don’t clean the machine while working.
• Do not put hands near the work piece when grinder is in motion.
• Don’t clean or adjust the machine while working.
• Check for oil on the floor while working (spilling of cutting fluid on floor while working)
• Check that the grinding wheel is running evenly.
  (Any 2 x 1) (2)

2.3 Gauges calibrated:

• To ensure accurate readings.
• To prevent overloading.
  (Any 1 x 1) (1)

2.4 Finger protectors’ hazards on power driven guillotines:

• The finger protector prevents the hazards of getting the fingers cut by the blades.
• To be crushed by the hold-downs. (2)

2.5 Welding or flame cutting operation safety:

• An operator has been instructed on how to use the equipment safely.
• A workplace is effectively partitioned off.
• An operator uses protective equipment.
• Ensure that all equipment is in safe working condition.
• Ensure that here are no flammable materials around the welding area.
• Weld area must be well ventilated.
• Fire extinguisher must be in close proximity.
  (Any 2 x 1) (2)

2.6 Workshop layout:

• Product layout. (1)

[10]

QUESTION 3: MATERIALS (GENERIC)
3.1 File test:
3.1.1 Difficult (1)
3.1.2 Easy (1)
3.1.3 Difficult (1)

3.2 Heat treatment:

• A. – Grain growth.
• B. – Recrystallisation.
• C. – Recovery. (3)

3.3 Bending test:

• Bend the test piece through a specific angle or around a mandrel or bar, having a defined radius, until a rupture in the metal occurs.
• Place the material in a vice and bend it then observe the ductility of the material.
  (Any 1 x 3) (3)

3.4 Purpose of case hardening:

• Creates a hard surface with a tough core. (2)

3.5 Quenching media for hardening:

• Water
• Brine (saltwater)
• Oil
• Soluble oil and water
• Nitrogen air-infused air
  (Any 3 x 1) (3)

[14]

QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC)
4.1 B (1)
4.2 B (1)
4.3 D (1)
4.4 C (1)
4.5 D (1)
4.6 A (1)
4.7 A (1)
4.8 B (1)
4.9 C (1)
4.10 B (1)
4.11 C (1)
4.12 B (1)
4.13 A (1)
4.14 D (1)
[14]

QUESTION 5: TERMINOLOGY (TEMPLATES) (SPECIFIC)
5.1 Dimensions of the material:
5.1.1

• Mean Ø = Outside Ø = Plate Thickness
  = 960 - 60 ?
  = 900 mm ? (2)

5.1.2

• \Mean circumference = π x Mean Ø
  = π x 900 ?
  = 2827,43 mm ?
  Round off to 2827 mm ? (3)

5.2 Welding symbols:
5.2.1 - 5.2.5

Each @ (2)
5.3 Templates:
5.3.1 Flange template (1)
5.3.2 Strip template (1)
5.3.3 Web template (1)

5.4 Hand tools: (Due to the large number of alternatives, marker discretion must be used - discuss with IM).

• Hand saws
• Chisels
• Plane
• Handdrill and drill bits
• Steel measuring tape
• Straight edge
• Compass
• Trammel pins
• Carpenter’s square
• Protractor
• Chalk line
• Steel rule
• Hammers
• Centre punch
• Callipers
• Scribe
• Combination square
• Spirit level
• Trammel
  (Any 3 x 1) (3)

5.5 Template loft machines: (Due to the large number of alternatives, marker discretion must be used - discuss with IM).

• Circular saw
• Planer
• Drilling machine
• Jig saw
• Sanding machine
• Shears for cutting cardboard
• Welding machine
• Angle grinder
• Bench grinder
• Guillotine
• Cut–off power saw
  (Any 2 x 1) (2)

[23]

QUESTION 6: TOOLS AND EQUIPMENT (SPECIFIC)
6.1 Operating principles of a resistance welding machine:

• Current flows through a resistance to fuse plates together. ?
• Two copper electrodes are pressed against the plates. ?
• Heavy current is passed between the electrodes. ?
• High resistance causes intense heat at the point. ?
• The two plates melt and fuse together, forming a weld nugget or spot weld. ? (5)

6.2 Arc welding:
6.2.1

• A. Arc welding machine / Power source / invertor. ?
• B. Earth clamp / “skelm” ?
• C. Electrode / Rod / welding rod ?
• D. Electrode holder (4)

6.2.2

• Holds the electrode.
• Insulate the person welding
• Provide current to the electrode
• Used with electrode to weld
  (Any 1 x 1) (1)

6.3 Cutting of threads:

• Secure the die in die wrench/stock and set die square to the shaft to be cut.
• Rotate the die through half a turn in a clockwise direction to cut the thread and then turn back a quarter of a turn to break off waste.
• Continue process until the die has reached the required length of thread and adjust the centre and side screws until desired thread fit is achieved. (6)

6.4 Advantages of using a punch machine:

• Can punch holes faster.
• Punch various hole profiles
• Less effort is needed 
  (Any 1 x 1) (1)

6.5 Pyramid rollers

• Rolling sheet metal.
• Used to roll round bars
  (Any 1 x 1) (1)

[18]

QUESTION 7: FORCES (SPECIFIC)
7.1 Beams:
7.1.1 Calculating reactions:
Taking moments about RL:

• RRx10 = (80?x 3 ) + (60x 5) + (100x 7)
  = 240 + 300 + 700
  RR = 1240/10
  = 124 N ?

Taking moments about RR:

• RLx10 = (100 ?x3 ) + (60x5 ) + (80 x 7 )
  = 300 + 300 + 560
  RL = 1160/10
  =116 N ? (8)

7.1.2 Calculating bending moments: Bending moments at B, C and D:

• BM_B =(116 x 3 )
  = 348Nm ?
  BM_C =(116 x 5 ) - (80 x 2 )
  = 420Nm ?
  BM_D = (116 x 7 ) - (80 x 4 ) - (60 x 2 )
  = 372Nm ? (3)

7.1. 3 Bending moment diagram:

(7)
NOTE: Draw the bending moment diagram to scale for marking purposes.
7.2 Stress and Strain:
7.2.1 Diameter of a bar:

(6)
7.2.2 Strain:

(2)
7.2.3 Change in length:

(3)
7.3 Stress and strain diagram:

• A: Limit of proportionality ?
• B: Elastic limit ?
• C: Yield point ?
• D: Maximum stress ?
• E: Break stress ? (5)

7.4 Simple frame:
7.4.1 Vector/Force diagram:

(5)

7.4.2 Magnitude and nature of force:

(6)
[45]

QUESTION 8: JOINING METHODS (INSPECTION OF WELDS) (SPECIFIC)
8.1 Arc welding aspects:

• Rate of rod burning and the progress of the weld
• Amount of penetration and fusion.
• Observe for welding defects while welding
• The sound of the arc indicating correct current and voltage for the particular weld.
• Angle of electrode.
• Arc length.
• Size of molten pool while welding
  (Any 3 x 1) (3)

8.2 Centreline cracks:

• Aiming at width to depth ratio of 1:1.
• Decreasing the current to prevent excess penetration.
• Decreasing welding voltage
• Slowing travel speed to achieve a flat to convex weld surface.
• Use clamping device.
• Pre – Heating
• Use of correct electrode
  (Any 2 x 1) (2)

8.3 Welding defects:
8.3.1 Lack of fusion:

• Travel speed is too slow.
• Wide weld joint.
• Weld current too low.
• Too big weaving action.
• Included angle not correct.
• Contaminated parent metal surface
• Weld metal not permitted to roll in front of arc.
• Arc not kept on leading edge of molten pool.
• Travel speed too fast.
• Excessive mill scale (iron oxide)
  (Any 2 x 1) (2)

8.3.2 Porosity:

• Contaminated weld surface.
• Wet or dirty electrodes.
• Shielding gas supply is interrupted.
• Welding in windy conditions.
  (Any 2 x 1) (2)

8.3.3 Incomplete penetration:

• Welding current too low.
• Welding speed too fast.
• Incorrect electrode angle.
• Poor joint preparation.
• Insufficient root gap.
• Electrode too big.
• Too long arc
• Contaminated weld surface.
  (Any 2 x 1) (2)

8.4 Setting oxy-acetylene torch flame to a neutral flame:

• Open acetylene torch valve ¼ turns or less and ignite.
• Adjust the acetylene torch valve further until the black smoke disappears.
• Open oxygen torch valve until the flame is no longer burning yellow.
• Inner cone of the flame must be rounded.
  (Any 3 x 1) (3)

8.5 Guided bend test:

• Specimen is placed across the supports of the die.
• Apply force to the specimen to bend into shape of the die.
• Determine the percentage of elongation of the weld metal. (3)

8.6 Free bend test:

• Determine the ductility of the weld.
• Determine the ductility of the heat – affected area adjacent to the weld.
• Determine the percentage of elongation
  (Any 2 x 1) (2)

8.7 Types of dye:

• Type A: Fluorescent that emits visible light when viewed using a Black light.
• Type B: Brightly coloured liquid dyes that can be inspected in regular light. (2)

8.8 Nick-break test:

• Determines internal quality of the weld metal.
• Reveals internal defects such as slag inclusions, porosity and lack of fusion.
  (Any 1 x 2) (2)

[23]

QUESTION 9: JOINING METHODS (STRESS AND DISTORTION) (SPECIFIC)
9.1 Causes of residual stress in welds:

• Heat present in the weld.
• Qualities of parent metal, filler rod or electrode.
• Shape and size of weld.
• Number of successive weld runs.
• Comparative weight of weld and parent metal.
• Type of welding joint used.
• Welding method used to mitigate stress and distortion.
• Type of structure of neighbouring joints.
• Freeness of joint to be able to expand and contract.
• Rate of cooling.
• Stresses already present in the parent metal.
  (Any 2 x 1) (2)

9.2 Factors of cooling rate:

• Size of work piece.
• Weld thickness.
• Thermal conductive properties of parent metal.
  (Any 3 x 1) (3)

9.3 Effect of cold working:

• The effect of cold working is to break down the crystal structure elongating the grains.
• An elongated and distorted crystal structure of this kind gives the metal greater hardness and tensile strength.
• Reduces ductility.
• Referred to as work hardening. (4)

9.4 Effects of welding speed on distortion:

• Increase in welding speed increases distortion due to larger flame in oxy-acetylene welding.
• Larger diameter electrode requires increased current causing more localised heat.
• Causing more residual stress.
• Causing more distortion.
  (Any 3 x 1) (3)

9.5 Quenching media:

• Water
• Oil
• Brine
• Liquid salts
• Sand
• Air
• Ash
• Lime
• Molten lead
• Nitrogen air-infused air
  (Any 3 x 1) (3)

9.6 Reducing welding distortion:

• Do not over-weld.
• Intermittent welding.
• Place welds near the neutral axis.
• Use a few passes as possible.
• Use back step welding.
• Anticipate the shrinkage forces.
• Use clamps, jigs and fixtures.
• Use strongbacks.
• Heating metal before welding. (pre- heating)
• Slowing the cooling rate
  (Any 3 x 1) (3)

[18]

QUESTION 10: MAINTENANCE (SPECIFIC)
10.1 Locking out of machine:

• Isolation switches must be switched off. ?
• The only key to the lock is in possession of the person carrying out the maintenance / Each maintenance person must have own lock. ? (2)

10.2 Tagging plates:

• More than one technician can lock out machine simultaneously. ? (1)

10.3 Minor service for a power-driven guillotine:

• The minor service is designed to minimise ? major mechanical and electrical failures. ? (2)

10.4 Cutting fluid:

• Keep the blade cool.?
• Keep the work piece cool ?
• Prolong the life span of the blade ?
• Washes cuttings away ?
• Improves cutting efficiency ?
• Reduces friction during cutting process. ?
• Better finish given to workpiece. ?
• Also prevents further corrosion. ?
  (Any 2 x 1) (2)

10.5 Overloading a rolling machine:

• Limit the life span of components ?
• Can result in costly damage ?
• Damage to bearings/bushes ?
• Damage to gearbox ?
• Damage to motor ?
  (Any 1 x 1) (1)

[8]

QUESTION 11: TERMINOLOGY (DEVELOPMENTS) (SPECIFIC)
11.1 True length of AC:

• AC² =  AB² + BC²
  but BC = 90 - 50
                     2
  = 40/2
  = 20 mm
  AC² = AB² + BC²
  = 50² + 20²
  AC =√ 2500 +  400
  = 53,85mm
  = 54mm (6)

11.2 Development:

• Square/rectangle ? to round ? transformer / transition piece / on centre. ? (3)

11.3 Square to rectangle on centre hopper:
11.3.1 True length of A-1:

• A - 1 = √200² + 130² + 500²
  = √40000 + 16900 + 250000
  = √306900
  = 553,99
  = 554 mm (4)

11.3.2 True length of C-2:

• C - 2 = √470² + 200² + 500²
  = √220900 + 40000 + 250000
  =  √510900
  = 714,77
  = 715 mm (4)

11.4 Hoppers:
11.4.1 Square to rectangle ? hopper off centre ? (2)
11.4.2 Square to square ? hopper on centre ? (2)
[21]

TOTAL: 200