Mechanical Technology Grade 12 NSC June 2024 Memo (English)

SENIOR CERTIFICATE EXAMINATIONS/ NATIONAL SENIOR CERTIFICATE EXAMINATIONS MECHANICAL TECHNOLOGY: FITTING AND MACHINING MAY/JUNE 2024 MARKING GUIDELINES MARKS: 200 These marking guidelines consist of 22 pages. Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 2 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC) 1.1 A ✓ (1) 1.2 B ✓ (1) 1.3 A ✓ (1) 1.4 D ✓ (1) 1.5 C ✓ (1) 1.6 C ✓ (1) [6] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 3 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 2: SAFETY (GENERIC) 2.1 First aid: • When illness occurs. ✓ • When an injury is sustained. ✓ • When an accident occurs. ✓ (Any 2 x 1) (2) 2.2 Bench grinder: A. A fire extinguisher should be readily available. ✓ B. Safety glasses must be worn. ✓ C. Maximum grinding wheel speed. ✓ D. Maximum distance between tool rest and grinding wheel. ✓ (4) 2.3 Drill press: • Never try to stop/hold the work piece by hand when the drill bit get stuck during drilling. ✓ • Don’t force a drill bit into the work piece. ✓ • Keep loose clothing and hair away from revolving parts. ✓ • Never leave the machine running if it is unattended. ✓ • Use a brush or wooden rod to remove chips from the drill. ✓ • Do not put hands near moving parts. ✓ • Never clean or adjust the machine while it is in motion. ✓ • Never try to stop the drill/chuck by hand. ✓ (Any 2 x 1) (2) 2.4 Surface grinder: • Never clean or adjust the machine while it is in motion. ✓ • Know how to stop the machine in an emergency. ✓ • Do not use excessive force when grinding the work piece. ✓ • Immediately report any dangerous defects of the machine. ✓ • Stop using defective machinery until it has been repaired by a qualified person. ✓ • Ensure that the grinding wheel is not submerged in coolant. ✓ • Never leave the machine running if it is unattended. ✓ • Do not put hands near moving parts. ✓ (Any 2 x 1) (2) [10] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 4 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 3: MATERIALS (GENERIC) 3.1 Critical temperature: 3.1.1 Hardening: Above ✓ (1) 3.1.2 Tempering: Below ✓ (1) 3.1.3 Normalising: Above ✓ (1) 3.2 Machining test: • The chips heating colour ✓ • The chips curl ✓ (2) 3.3 Material tests: • Sound test ✓ • Bending test ✓ • Filing test ✓ • Hardness test ✓ • Density test ✓ • Weight measurement ✓ • Magnetic test ✓ • Visual inspection/observation ✓ • Scratch test ✓ (Any 3 x 1) (3) 3.4 Quenching methods: • Carburising ✓ • Nitriding ✓ • Cyaniding ✓ (Any 2 x 1) (2) 3.5 Heat treatment temperature: • Pyrometer ✓ • Crayons ✓ • Visually ✓ • Magnet ✓ (Any 1 x 1) (1) 3.6 Heat-treatment steps: • Heat the metal. ✓ • Soak the metal. ✓ • Cool the metal. ✓ (3) [14] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 5 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC) 4.1 B✓ (1) 4.2 C✓ (1) 4.3 B✓ (1) 4.4 C✓ (1) 4.5 D✓ (1) 4.6 D✓ (1) 4.7 C✓ (1) 4.8 A✓ (1) 4.9 B✓ (1) 4.10 A✓ (1) 4.11 B✓ (1) 4.12 A✓ (1) 4.13 A✓ (1) 4.14 D✓ (1) [14] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 6 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 5: TERMINOLOGY (LATHE AND MILLING MACHINE) (SPECIFIC) 5.1 Advantages of tailstock set-over method: • The automatic feed of the machine can be used. ✓ • Good finish. ✓ • Long tapers can be cut. ✓ • Accurate tapers can be cut. ✓ • Experience less operator fatigue. ✓ (Any 2 x 1) (2) 5.2 Taper calculations: 5.2.1 Tool: Boring bar. ✓ (1) 5.2.2 Diameter of taper: x θ D -d tan3,5 = tan = 155  2 2l x = tan3,5  155   7 46 − d ✓ tan = = 9,46 mm  2 2  155  OR ✓ d = 46 − 2 x  310 tan3, 5 = 46 ✓ −d d =46 − 18, 96 = 46 − 2(9,46 )  d =27, 04 mm ✓ = 27,04 mm  (6) 5.3 Calculation of parallel key: 5.3.1 D Width = 4 82 ✓ = 4 = 20, 50 mm ✓ (2) 5.3.2 D Thickness = 6 82 ✓ = 6 = 13, 67 mm ✓ (2) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 7 DBE/May/June 2024 SC/NSC – Marking Guidelines 5.3.3 Lenght = 1,5  diameter of shaft = 1,5  82 ✓ = 123 mm ✓ (2) 5.4 Advantages of gang milling: • Several surfaces can be milled simultaneously. ✓ • Saving time. ✓ • Makes production more effective. ✓ • Fewer cutters need to be changed. ✓ (Any 3 x 1) (3) [18] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 8 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 6: TERMINOLOGY (INDEXING) (SPECIFIC) 6.1 Gear calculations: 6.1.1 Number of teeth: PCD Module = T PCD ✓ T= m 156 = ✓ 3 = 52 teeth ✓ (3) 6.1.2 Dedendum: Dedendum = 1,157 (m) = 1, 25 ( m) = 1,157  3 ✓ OR = 1, 25  3 ✓ = 3, 47 mm ✓ = 3, 75 mm ✓ (2) 6.1.3 Outside diameter: OD = PCD + 2 ( m) = m ( T + 2) = 156 + 2 ( 3 ) ✓ OR = 3 ( 52 + 2 ) ✓ = 162 mm ✓ = 162 mm ✓ (2) 6.1.4 Circular pitch: CP = m π = 3π ✓ = 9, 42mm ✓ (2) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 9 DBE/May/June 2024 SC/NSC – Marking Guidelines 6.2 Dove tail calculations: W = 145 + 2(DE) m = W - 2 (AC) - 2 (R) or m = W - 2 ( AC +R) 6.2.1 Maximum width of dove tail (W): Calculate DE: AD tanθ = ✓ DE ✓ DE tan = AD AD tan60  = ✓ DE = AD tan ✓ OR DE = 32 tan30 32 DE = = 18, 48 mm ✓ tan60  = 18,48 mm ✓ W = 145 + 2 ( DE ) ✓ = 145 + 2 (18, 48 ) ✓ = 145 + 36, 96 = 181,96 mm ✓ (6) 6.2.2 Distance between the rollers (m): Calculate AC: BC tan α = ✓ AC AC BC tan θ = ✓ AC = ✓ BC tan  OR AC = BC tan60  ✓ 12 = 12 tan60  = tan30 = 20,78 mm ✓ = 20, 78mm ✓ m = W − 2 ( AC ) − 2 (R ) ✓ m = W − 2 (AC + R ) ✓ = 181, 96 − 2 ( 20, 78 ) − 2 (12 ) ✓ = 181,96 − 2 (20,78 + 12) ✓ OR = 181, 96 − 41, 56 − 24 = 181,96 − 65,56 = 116, 40 mm ✓ = 116,40 mm ✓ (6) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 10 DBE/May/June 2024 SC/NSC – Marking Guidelines 6.3 Milling of spur gear: 6.3.1 Indexing: 40 Indexing = n 40 Indexing = A 40 = 160 ✓ 1 6 =  4 6 6 = 24 ✓ Approximate indexing: No full turns and 6 holes on a 24-hole circle ✓ OR No full turns and 7 holes on a 28-hole circle ✓ (3) 6.3.2 Change gears: D DR 40 = (A − n)  D DN A D DR 40 = (160 − 163 )  ✓ D DN 160 40 =−3  160 − 120 = 160 3 8 =  ✓ 4 8 D DR 24 ✓ = D DN 32 ✓ (4) [28] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 11 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 7: TOOLS AND EQUIPMENT (SPECIFIC) 7.1 Define hardness: Hardness is a material’s ability to resist deformation, ✓ usually by indentation/penetration/scratching. ✓ (2) 7.2 Hardness testers: • Brinell hardness tester ✓ • Rockwell hardness tester ✓ • Vickers hardness tester ✓ (Any 2 x 1) (2) 7.3 Microscope: To measure ✓ the diameter/depth of the indentation ✓ left in the test material. (2) 7.4 Tester: 7.4.1 Tensile tester ✓ (1) 7.4.2 Hand wheel ✓ (1) 7.5 Hardness tester: Rockwell hardness tester ✓ (1) 7.6 Moment and Force: Test the reaction ✓ on either side of simply loaded beam. ✓ (2) 7.7 Reading: ✓ ✓ 2,00 + 0,40 + 0,5 = 2, 90 mm (2) [13] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 12 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 8: FORCES (SPECIFIC) 8.1 Forces: 8.1.1 Horizontal components:  HC = 75cos35 − 15cos45 − 5cos0 − 45cos60 ✓ ✓ ✓ ✓  HC = 61,44 − 10,61 − 5 − 22,5  HC = 23,33 N ✓ (5) 8.1.2 Vertical components:  VC = 75sin35 + 15sin45 − 5sin0 − 45sin60 ✓ ✓ ✓  VC = 43,02 + 10,61 − 0 − 38,97  VC = 14,66 N ✓ (4) OR Force θ 8.1.1 ∑HC/x = Fcosθ 8.1.2 ∑VC/y = Fsinθ 25 N 90º HC = 75cos35° 61,44 N ✓ VC = 75sin35° 43,02 N ✓ 40 N 0º HC = 15cos135° 10,61 N ✓ VC = 15sin135° 10,61 N ✓ 55 N 290º HC = 5cos180° -5 N ✓ VC = 5sin180° 0N 120 N 210º HC = 45cos240° -22,5 N ✓ VC = 45sin240° -38,97 N ✓ Total 23,33 N ✓ 14,66 N ✓ (9) 8.1.3 Resultant: R 2 = VC 2 + HC 2 R= (14,66 )2 + (23,33 )2 ✓ R = 759,20 R = 27,55N ✓ (2) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 13 DBE/May/June 2024 SC/NSC – Marking Guidelines 8.1.4 Angle and direction of resultant: Angle: VC HC tanθ = tanθ = HC VC  14,66  ✓  23,33  ✓ θ = tan−1   OR θ = tan−1    23,33   14,66  θ = tan−1 (0,63 ) θ = tan−1 (1,59 ) θ = 32,14 ✓ θ = 57,86 ✓ Direction: N R R = 27,55 N 32,14  North of East ✓ θ E OR R = 27,55 N 57,86  East from North (3) 8.2 UDL Beam: 8.2.1 Distributed load: Uniform distributed load: UDL = 15  6 ✓ = 90 N ✓ (2) 8.2.2 Reaction in support A: Take moments about B: ✓ ✓ ✓ (160  2,5 ) + (90  7) + (55  14) = (A  14) 400 + 630 + 770 = 14A 1800 A= 14 A = 128,57N ✓ Reaction in support B: Take moments about A: ✓ ✓ (B  14) = (55  0) + (90  7) + (160  11,5 ) 14B = 0 + 630 + 1840 2470 B= 14 B = 176,43 N ✓ (7) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 14 DBE/May/June 2024 SC/NSC – Marking Guidelines 8.3.1 Diameter: F π  d2 σ= A= A 4 F ✓ A = ✓ 4A σ d= ✓ π A = 3,19  10 −4 OR 4 ( 3,19  10 −4 ) ✓ d= π πd2 = 3,19  10 −4 ✓ 4 = 0, 02015 m π  d2 = 1,28  10 −3 = 20,15 mm ✓ d2 = 4,06  10 −4 ✓ d = 0,02015 m d = 20,15 mm ✓ (4) 8.3.2 Change in length: σ E = ε σ ε= E ✓ 56,5  10 6 ε= ✓ 90  10 9 ε = 6,28  10 − 4 ✓ ΔL ε= oL ΔL = ε  oL ✓ ΔL = 6,28  10 −4  0,275 ✓ ΔL = 1,73  10 −4 m ( ) ΔL = 1,73  10 −4  1000 ΔL = 0,17 mm ✓ (6) [33] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 15 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 9: MAINTENANCE (SPECIFIC) 9.1 Preventative maintenance: • Checking for wear and tear on belt. ✓ • Checking belt alignment. ✓ • Checking the tensioning devices. ✓ • Checking the tensioning setting. ✓ • Make sure all guards are in place. ✓ • Checking for dirt on belt and pulleys. ✓ (Any 4 x 1) (4) 9.2 High power drives: • Gear drive ✓ • Multiple belt drives ✓ • Tooth belt drives ✓ • Chain drives ✓ (Any 2 x 1) (2) 9.3 Bonding methods: • Plastic welding (heat) ✓ • Adhesive/PVC-Weld ✓ (2) 9.4 Uses of the materials: 9.4.1 Nylon: • Pulleys ✓ • Ropes ✓ • Bushes ✓ • Gears ✓ • Wear pads ✓ • Wheels ✓ • Rollers ✓ • Gaskets ✓ • Seals ✓ • Machinery parts ✓ (Any 2 x 1) (2) 9.4.2 Fibreglass: • Machine covers ✓ • Roof covering ✓ • Woven cloth ✓ (Any 2 x 1) (2) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 16 DBE/May/June 2024 SC/NSC – Marking Guidelines 9.4.3 Bakelite uses: • Circuit boards ✓ • Electrical components ✓ • Electrical insulators ✓ • Kitchenware ✓ • Jewellery ✓ • Pipe stems ✓ • Toys ✓ • Distributor rotor ✓ • Distributor cap ✓ • Aircraft components ✓ • Bearings ✓ • Clutch linings ✓ • Brake linings ✓ • Laminated materials ✓ (Any 2 x 1) (2) 9.5 Thermo-hardened/Thermosetting or Thermoplastic composite: 9.5.1 Thermoplastic ✓ (1) 9.5.2 Thermo-hardened / Thermosetting ✓ (1) 9.5.3 Thermo-hardened / Thermosetting ✓ (1) 9.5.4 Thermoplastic ✓ (1) [18] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 17 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 10: JOINING METHODS (SPECIFIC) 10.1 Uses of multiple threads: • Fire hydrants ✓ • Valves ✓ • Aircraft landing gear ✓ • Industrial machines ✓ • Lids of containers/jars ✓ • Fly press ✓ (Any 3 x 1) (3) 10.2 Multiple screw threads: • They provide more bearing surface. ✓ • Do not strip easily. ✓ • To provide faster linear movement. ✓ • They are more efficient. ✓ • They lose less power to friction. ✓ (Any 3 x 1) (3) 10.3 Square Thread: 10.3.1 Pitch: Lead Pitch = Number of starts 46 = 2 ✓ = 23 mm ✓ (2) 10.3.2 Pitch diameter: P Dm = OD − 2 23 ✓ = 80 − 2 = 68, 50 mm  (2) 10.3.3 Helix angle of the thread: Lead tan θ = π  DM 46 = ✓ π  68,50 ✓ θ =✓tan −1 (0,213755544 ) = 12,07 or 124' ✓ (4) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 18 DBE/May/June 2024 SC/NSC – Marking Guidelines 10.3.4 Leading tool angle: Leading tool angle = 90 − (helix + clearance angle ) = 90 − (12,07 + 3) ✓ = 74,93 or 7455' ✓ (2) 10.3.5 Following tool angle: Following tool angle = 90 + (helix − clearance angle ) = 90 + (12,07 − 3) ✓ = 99,07 or 994' ✓ (2) [18] Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 19 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 11: SYSTEMS AND CONTROL (DRIVE SYSTEMS) (SPECIFIC) 11.1 Hydraulic calculations: 11.1.1 The fluid pressure in the hydraulic system in MPa: π d2 A (Plunger ) = 4 π(0,03) 2 A = ✓ 4 A = 0,71  10 −3 m2 ✓ F P= A 900 ✓ P= 0,71  10 ✓ -3 P = 1,27  106 Pa ✓ P = 1,27 MPa (5) 11.1.2 Mass in kg: FA F = B A A AB FA  A B FB = ✓ AA 900  31, 42  10 -3 ✓ FB = 0, 71  10-3 ✓ FB = 39828,17 N Mass = 3982, 82 kg OR 4059, 96 kg ✓ (4) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 20 DBE/May/June 2024 SC/NSC – Marking Guidelines 11.2 Function of hydraulic components: 11.2.1 Motor Drives the hydraulic pump. ✓ (1) 11.2.2 One-way-valve To prevent backflow of hydraulic fluid. ✓ (1) 11.2.3 Reservoir Contains the hydraulic fluid. ✓ (1) 11.3 Belt drive: 11.3.1 The rotational frequency in r/sec: NDR  DDR = NDN  DDN NDR  DDR = NDN  DDN NDN  DDN NDN  DDN NDR = ✓ NDR = ✓ DDR DDR 5,83  0,5 OR 350  500 NDR = ✓ NDR = ✓ 0,09 90 2,92 1944,44 r/min NDR = NDR = 0,09 60 NDR = 32,39 r/sec ✓ NDR = 32,41 r/sec ✓ (3) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 21 DBE/May/June 2024 SC/NSC – Marking Guidelines 11.3.2 Power transmitted in Watt: Ρ= ( T1 − T2 ) π D N 60 ✓ ✓ ✓ Ρ = (1900 − 450 ) π  0, 09  32, 39 P = 13279,18 W ✓ OR Ρ= ( T1 − T2 ) π D N 60 ✓ ✓ ✓ Ρ = (1900 − 450 ) π  0, 5  5, 83 P = 13278, 73 W ✓ OR Ρ= ( T1 − T2 ) π D N 60 ✓ ✓ ✓ Ρ = (1900 − 450 ) π  0, 5  350 P = 13286, 32 W ✓ (4) 11.4 Avoid slipping: • Adding a belt tensioning device. ✓ • Not subjected to sudden loads. ✓ • Do not overload the drive. ✓ • Cover the drives to guard against dust and fluids. ✓ • Increase the contact area of the belts. ✓ • Use toothed belts and pulleys. ✓ (2) (Any 2 x 1) Copyright reserved Please turn over

Mechanical Technology: Fitting and Machining 22 DBE/May/June 2024 SC/NSC – Marking Guidelines 11.5 Gear drive: 11.5.1 Number of teeth: Ninput Product of teethon driven gears = Noutput Product of teethon driver gears NA T  TD = B ND T A  TC N  T A  TC TD = A ✓ ND  TB 3500  33  25 TD = ✓ 1050  55 TD = 50 teeth ✓ (3) 11.5.2 Torque: 2 π NT P = 2 π NT P= 60 P T= T= P  60 2π N ✓ 2π N ✓ OR (737,4  103 ) T = (737,4  10 )  60 2  π  17,5 ✓ 3 T = ✓ 2  π  1050 T = 6706,33 Nm ✓ T = 6706,33 Nm ✓ (3) [28] TOTAL: 200 Copyright reserved