Mechanical Technology Grade 12 NSC June 2023 QP (Eng)

Downloaded from hlayiso.com SENIOR CERTIFICATE EXAMINATIONS/ NATIONAL SENIOR CERTIFICATE EXAMINATIONS MECHANICAL TECHNOLOGY: FITTING AND MACHINING 2023 MARKS: 200 TIME: 3 hours This question paper consists of 19 pages and a 6-page formula sheet. Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 2 DBE/2023 SC/NSC INSTRUCTIONS AND INFORMATION 1. Write your centre number and examination number in the spaces provided on the ANSWER BOOK. 2. Read ALL the questions carefully. 3. Answer ALL the questions. 4. Number the answers correctly according to the numbering system used in this question paper. 5. Start EACH question on a NEW page. 6. Show ALL calculations and units. Round off final answers to TWO decimal places. 7. Candidates may use non-programmable scientific calculators and drawing instruments. 8. The value of gravitational acceleration should be taken as 10 m/s 2. 9. All dimensions are in millimetres, unless stated otherwise in the question. 10. Write neatly and legibly. 11. A formula sheet is attached at the end of the question paper. 12. Use the criteria below to assist you in managing your time. TIME QUESTION CONTENT MARKS IN MINUTES GENERIC 1 Multiple-choice Questions 6 6 2 Safety 10 10 3 Materials 14 14 SPECIFIC 4 Multiple-choice Questions 14 10 5 Terminology (Lathe and Milling Machine) 18 20 6 Terminology (Indexing) 28 25 7 Tools and Equipment 13 10 8 Forces 33 33 9 Maintenance 18 12 10 Joining Methods 18 12 11 Systems and Control (Drive Systems) 28 28 TOTAL 200 180 Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 3 DBE/2023 SC/NSC QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC) Various options are provided as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question numbers (1.1 to 1.6) in the ANSWER BOOK, e.g. 1.7 E. 1.1 Which ONE of the following safety precautions is applicable to the bench grinder? A Oil the surface of the machine. B Remove all guards when grinding. C Wear safety goggles when grinding. D Ensure that the machine is on. (1) 1.2 What does the Occupational Health and Safety Act state regarding HIV/Aids awareness? A All employers must make sure that the workplace is safe, and that employees are not at risk of contracting HIV. B It does not contain common guidelines on how employers, employees and trade unions should respond to persons with HIV in the workplace. C Employers may demote or promote an employee based on his/her HIV status. D Employers can simply dismiss a person who has HIV. (1) 1.3 Which ONE of the following procedures is applicable when applying basic medical treatment? A Examine the injured person. B Remove the object from the wound. C Use an oily substance or lotion on a burn. D Phone the insurance company. (1) 1.4 Why is steel heated slowly to a certain temperature during heat treatments? To ensure that … A high heat is obtained. B the room temperature is correct. C a uniform temperature is obtained. D the safety process is correct. (1) 1.5 Which ONE of the following is an example of case-hardening? A Frying pans B Gears C Wheel rims D Chisels (1) 1.6 What does the term quenching rate during heat treatment mean? A Cooling rate B Heating rate C Tempering rate D Hardening rate (1) [6] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 4 DBE/2023 SC/NSC QUESTION 2: SAFETY (GENERIC) 2.1 Which safety precaution must be adhered to after the work on any machine is completed? (1) 2.2 Give TWO reasons why the space between the tool rest and the grinding wheel on a bench grinder must not exceed 3 mm. (2) 2.3 Identify the workshop layouts shown in FIGURES 2.3.1 and 2.3.2 below. 2.3.1 FIGURE 2.3.1 (1) 2.3.2 FIGURE 2.3.2 (1) 2.4 State ONE type of personal protective equipment that must be worn when working on a hydraulic press machine. (1) 2.5 State ONE function of the safety guard on a portable angle grinder. (1) 2.6 State ONE safety precaution, other than environmental safety, that must be observed when using a shearing machine/guillotine. (1) 2.7 State TWO safety precautions that must be adhered to when storing gas cylinders. (2) [10] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 5 DBE/2023 SC/NSC QUESTION 3: MATERIALS (GENERIC) 3.1 Why is tempering of steel done after hardening? (2) 3.2 Give ONE reason for EACH of the following heat-treatment processes on steel: 3.2.1 Case hardening (2) 3.2.2 Annealing (2) 3.3 Explain how to conduct a spark test to identify the type of steel. (2) 3.4 Explain how you will conduct the following tests: 3.4.1 Filing test (2) 3.4.2 Bend test (2) 3.5 What sound do the following materials make when performing a sound test? 3.5.1 Low-carbon steel (1) 3.5.2 High-carbon steel (1) [14] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 6 DBE/2023 SC/NSC QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC) Various options are provided as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question numbers (4.1 to 4.14) in the ANSWER BOOK, e.g. 4.15 E. 4.1 What is the use of the centre lathe machine component in FIGURE 4.1 below? It supports … FIGURE 4.1 A centre drilling. B the work piece on the lathe. C setting up a centre gauge. D the dead centre. (1) 4.2 Which ONE of the following milling cutters can be used to cut a keyway a certain distance from the shaft end? A Helical cutter B Flute mill C Shell mill D Rotation mill (1) 4.3 The size of the centrifugal force depends on the ... A mass of the rotating element. B extent to which the mass is on centre. C amount of braking power applied to the work piece. D specific machine that is used. (1) 4.4 What does the abbreviation CNC stand for? A Computer naming control B Computer negative control C Computer neutral control D Computer numerical control (1) 4.5 Identify the precision tool that is used to measure the length of a cylinder: A Outside micrometer B Inside micrometer C Depth micrometer D Screw-thread micrometer (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 7 DBE/2023 SC/NSC 4.6 Identify the type of hardness tester in FIGURE 4.6 below. FIGURE 4.6 A Pascal hardness tester B Tensile hardness tester C Brinell hardness tester D Moment hardness tester (1) 4.7 What is the definition of equilibrant? A An equilibrant has the same magnitude as a resultant and acts in the same line of action, but in the opposite direction. B An equilibrant has a different magnitude than a resultant and acts in a different line of action, but in the opposite direction. C An equilibrant has the same magnitude as a resultant and acts in a different line of action, but in the same direction. D An equilibrant has a different magnitude than a resultant and acts in the same line of action, but in the opposite direction. (1) 4.8 How is Young's modulus defined? A It is the ratio between the hardness and strain on the surface of a metal, providing that the limit of elasticity is not exceeded. B It is the ratio between the stress and strain in a metal, providing that the limit of elasticity is not exceeded. C It is the ratio between the stress and load on a metal, providing that the limit of elasticity is exceeded. D It is the ratio between the force and strain outside a metal, providing that the limit of elasticity is not exceeded. (1) 4.9 Which ONE of the following is an application of Vesconite? A Artificial leather B Bearings and bushes C Window panels D Roof panels (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 8 DBE/2023 SC/NSC 4.10 How is polyvinyl chloride (PVC) joined? A Arc welding B Air blower C Brazing D Adhesive 4.11 Why are the crest and the root of metric V-screw threads rounded? A For safety reasons B To strengthen the screw thread C Allow for smoother movement D Prevent screw thread from stripping (1) 4.12 What is the included angle of a metric V-screw thread? A 60° B 30° C 55° D 29° (1) 4.13 How can torque be described? It is the ... effect of a force. A turning B compressive C tensile D pressing (1) 4.14 Identify the hydraulic symbol in FIGURE 4.14 below. FIGURE 4.14 A Hydraulic pump B Hydraulic filter C Hydraulic motor D Hydraulic reservoir (1) [14] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 9 DBE/2023 SC/NSC QUESTION 5: TERMINOLOGY (LATHE AND MILLING MACHINE) (SPECIFIC) 5.1 FIGURE 5.1 below shows a screw-cutting dial found on a lathe machine. Label parts A–C. B A C FIGURE 5.1 (3) 5.2 FIGURE 5.2 below shows a diagram of a taper with an included angle of 11°, which should be machined between two centres. 11° 45 65 L FIGURE 5.2 Calculate the following: 5.2.1 The length of the taper (4) 5.2.2 The set-over of the tailstock required to cut the taper (3) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 10 DBE/2023 SC/NSC 5.3 A parallel key suitable for a 70 mm diameter shaft is needed in a forklift gearbox. Calculate the following key dimensions: 5.3.1 Width (2) 5.3.2 Thickness (2) 5.3.3 Length (2) 5.4 Calculate the mean diameter for a two-start square thread that has an outside diameter of 38 mm and a pitch of 4 mm. (2) [18] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 11 DBE/2023 SC/NSC QUESTION 6: TERMINOLOGY (INDEXING) (SPECIFIC) 6.1 Willy is a machinist and is tasked to cut a spur gear with a pitch-circle diameter of 120 mm and a module of 3. Calculate the following: 6.1.1 Number of teeth (3) 6.1.2 Dedendum (2) 6.1.3 Outside diameter (2) 6.1.4 Circular pitch (2) 6.2 FIGURE 6.2 below shows an external dovetail that must be manufactured for a compound slide on a lathe machine. y w y D E h = 32 θ B θ 10 .2. 4 12 10 A C x 10 112,32 10 x 166,96 FIGURE 6.2 Calculate the following: 6.2.1 The angle θ (6) 6.2.2 Minimum width (w) distance of the dovetail (6) 6.3 Dinnesh is required to mill a spur gear with 137 teeth for an engineering client. The dividing head he is using has a ratio of 40 : 1. HINT: Use A = 140 divisions for the simple indexing. Calculate the following: 6.3.1 The indexing that is needed (3) 6.3.2 The change gears that are required (4) [28] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 12 DBE/2023 SC/NSC QUESTION 7: TOOLS AND EQUIPMENT (SPECIFIC) 7.1 Name the different types of indenters used in the following hardness testers: 7.1.1 Rockwell hardness tester (1) 7.1.2 Brinell hardness tester (1) 7.2 FIGURE 7.2 below shows a Rockwell hardness tester. Label A–D. A B D C FIGURE 7.2 (4) 7.3 What is represented by the following in an M10 x 1,25 screw thread? 7.3.1 M (1) 7.3.2 10 (1) 7.3.3 1,25 (1) 7.4 FIGURE 7.4 below shows a screw thread micrometer. Label A–D. A B C D FIGURE 7.4 (4) [13] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 13 DBE/2023 SC/NSC QUESTION 8: FORCES (SPECIFIC) 8.1 FIGURE 8.1 below shows a system of forces with three tensile forces and one compressive force acting onto the same point. 40 N 25 N 70º 55 N 60º 120 N FIGURE 8.1 HINT: To assist you, draw and complete the force diagram shown in FIGURE 8.1. Show ALL the horizontal (HC) and vertical components (VC) before you do the calculations. Calculate the following: 8.1.1 The sum of the horizontal components (4) 8.1.2 The sum of the vertical components (4) 8.1.3 The magnitude of the resultant (2) 8.1.4 The angle of the resultant (2) 8.1.5 The direction of the resultant (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 14 DBE/2023 SC/NSC 8.2 FIGURE 8.2 below shows a uniform beam that is supported by two vertical supports, A and B. Two vertical point loads and one uniformly distributed load (UDL) are exerted onto the beam. 75 N 60 N 10 N/m (UDL) 3m 9m A B FIGURE 8.2 Calculate the following: 8.2.1 The point load representing the uniformly distributed load (UDL) (1) 8.2.2 The magnitude of the reaction force at A (4) 8.2.3 The magnitude of the reaction force at B (5) 8.3 A load of 45 kN causes a compressive stress of 9 MPa in a square brass bar. The change in length caused by the load on the square bar is 0,15 mm and Young's modulus for brass is 90 GPa. Calculate the following: 8.3.1 The side length of the resistance surface in mm (4) 8.3.2 The strain (3) 8.3.3 The original length in mm (3) [33] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 15 DBE/2023 SC/NSC QUESTION 9: MAINTENANCE (SPECIFIC) 9.1 Why is it necessary to conduct maintenance on an operating system? (2) 9.2 Name THREE different types of belts used in belt-drive systems. (3) 9.3 State THREE preventative maintenance procedures to ensure that chain drives work properly. (3) 9.4 State TWO properties of EACH of the following composites: 9.4.1 Nylon (2) 9.4.2 Fibreglass (2) 9.4.3 PVC (2) 9.5 State ONE use of EACH of the following composites: 9.5.1 Bakelite (1) 9.5.2 Carbon fibre (1) 9.5.3 Nylon (1) 9.6 Is Vesconite reliable when used as a bush in a drive system? (1) [18] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 16 DBE/2023 SC/NSC QUESTION 10: JOINING METHODS (SPECIFIC) 10.1 Bianca needs to manufacture a two-start square threaded bar. The lead of the square thread is 46 mm and the crest diameter is 85 mm. The clearance angle on the cutting tool must be 3°. Calculate the following: 10.1.1 Pitch diameter (5) 10.1.2 Helix angle (3) 10.1.3 Leading tool angle (2) 10.1.4 Following tool angle (2) 10.2 FIGURE 10.2 below shows a square screw thread. Label A–D. C A B Cutting Tool D FIGURE 10.2 (4) 10.3 Explain how the sides of cutting tools must be ground in order to cut a square thread. (2) [18] Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 17 DBE/2023 SC/NSC QUESTION 11: SYSTEMS AND CONTROL (DRIVE SYSTEMS) (SPECIFIC) 11.1 FIGURE 11.1 below shows a hydraulic press. A force of 85 N acts on the plunger that moves 90 mm. The area of the plunger is 0,25 m² and the area of the ram is 2,1 m². 85 N F=? PLUNGER 90 mm L=? RAM 'A' 'B' FLUID FIGURE 11.1 Calculate the following: 11.1.1 The fluid pressure in the hydraulic system in Pa (2) 11.1.2 The displacement of the ram in mm (L) (3) 11.1.3 The force exerted by the ram (3) 11.2 Name TWO types of hydraulic pumps. (2) 11.3 Identify the type of hydraulic valve in FIGURE 11.3 below. FIGURE 11.3 (1) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 18 DBE/2023 SC/NSC 11.4 FIGURE 11.4 below shows a V-belt drive system of a compressor. The driver pulley of the belt drive system rotates at 2 700 r/min and has a diameter of 210 mm. The compressor shaft must rotate at 1 000 r/min. NDN = 1 000 r/min DDN = ? mm NDR = 2 700 r/min DDR = 210 mm Compressor Motor FIGURE 11.4 Calculate the following: 11.4.1 The diameter of the driven/compressor pulley in mm (3) 11.4.2 The power transmitted, in kW, if the effective force in the belt is 400 N (4) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 19 DBE/2023 SC/NSC 11.5 FIGURE 11.5 below shows a gear drive system on the shaft of an electric motor. NA =? r/min TA = 40 TC = 18 ND = 800 r/min Output shaft Electric motor Counter shaft TB = 22 TD = 40 FIGURE 11.5 Calculate the following: 11.5.1 The rotation frequency of the electric motor in r/s if the output shaft rotates at 800 r/min (4) 11.5.2 The speed ratio (3) 11.6 An output shaft of a chain drive rotates at 5 r/s. Calculate the torque if the drive transmits 11 kW of power. (3) [28] TOTAL: 200 Copyright reserved

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 1 DBE/2023 SC/NSC FORMULA SHEET FOR MECHANICAL TECHNOLOGY: FITTING AND MACHINING 1. BELT DRIVES πDN 1.1 Belt speed = 60 π D  t   N 1.2 Belt speed = (t = belt thickness) 60 1.3 Belt mass = Area × Length × Density (A = thickness × width) Diameter of driven pulley 1.4 Speed ratio = Diameter of driver pulley 1.5 Belt length (flat) = [(D + d) × 1,57] + ( 2 × centre distance) π D  d  D  d  2 1.6 Open belt length =   2c 2 4c π D  d  D  d  2 1.7 Crossed belt length =   2c 2 4c 1.8 Power (P) = T1  T2  π D N 60 Where: T1 = force in the tight side T2 = force in the slack side T1 – T2 = effective tensile force (Te) T1 1.9 Ratio between tight side and slack side = T2 T1 1.10 Width = Permissible tensile force 1.11 NDR × DDR = NDN × DDN Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 2 DBE/2023 SC/NSC 2. STRESS AND STRAIN Ashaft = π d 2 2.1 4 Apipe = π D  d  2 2 2.2 4 Maximum stress/Break stress 2.3 Safety factor = Safe working stress Force F 2.4 Stress = OR σ Area A Change in length ΔL 2.5 Strain = OR ε Original length OL Stress σ 2.6 Young’s modulus = OR E Strain ε 3. HYDRAULICS Force F 3.1 Pressure = OR P Area A 3.2 Volume = Area × Stroke length (l or s) 3.3 Work done = Force × distance 3.4 PA = PB FA FB 3.5  AA AB 4. GEAR DRIVES 2π NT 4.1 Power (P) = 60 Product of teeth on driven gear Ninput 4.2 Gear Ratio = OR Speed ratio = Product of teeth on driver gear Noutput Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 3 DBE/2023 SC/NSC Ninput Product of teeth on driven gear 4.3 = Noutput Product of teeth on driver gear 4.4 NA × TA = NB × TB 4.5 Torque = Force × Radius 4.6 Torque transmitted = Gear ratio × Input torque Pitch-circle diameter PCD 4.7 Module = OR m= Number of teeth T Circular pitch × Number of teeth 4.8 Pitch-circle diameter = π OR CPT PCD =  4.9 Outside diameter (OD) = PCD + 2(m) 4.10 Addendum = Module OR a=m 4.11 Dedendum (b) = 1,157 × m OR Dedendum (b) = 1,25 × m 4.12 Cutting depth (h) = 2,157 × m OR Cutting depth (h) = 2,25 × m 4.13 Clearance (c) = 0,157 × m OR Clearance (c) = 0,25 × m 4.14 Circular pitch (CP) = m × π 4.15 Working depth (WD) = 2 × m OR Working depth (WD) = 2 × a 5. PULLEYS 5.1 NDR × DDR = NDN × DDN 2π NT 5.2 Power (P) = 60 Diameter of driven pulley 5.3 Velocity ratio = Diameter of driver pulley Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 4 DBE/2023 SC/NSC 6. KEYWAYS D 6.1 Width (W) = 4 D 6.2 Thickness (T) = 6 6.3 Length (L) = 1,5 × D Where: D = Diameter of shaft 6.4 Standard taper for taper key: 1 in 100 or 1 : 100 7. CINCINNATI DIVIDING HEAD TABLE FOR MILLING MACHINE Hole circles 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 Change gears Gears 24 × 2 28 32 40 44 48 56 64 72 86 100 40 7.1 Indexing = (n = number of divisions) n Dr A  n 40   A  n  Dr 40 7.2   OR Dn A 1 Dn A Where: A = chosen number of divisions n = real number of divisions 8. DOVETAILS Where: R = Radius of precision roller y = Distance from top edge of dovetail in relation to bottom corner of dovetail x = Distance from middle of precision roller to bottom corner of dovetail θ = Dovetail included angle (normally 60°) h = Height of dovetail w = Minimum width of dovetail W = Maximum width of dovetail m = Distance between rollers M = Distance over rollers Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 5 DBE/2023 SC/NSC 9. TAPERS θ D-d 9.1 tan = (l = Taper length) 2 2l LD - d  9.2 Tailstock setover = (L = Distance between centres) 2l 10. SCREW THREADS P 10.1 Mean diameter = Outside diameter – (½ × Pitch) OR Dm = OD ‒ 2 10.2 Effective diameter (Deff) = Pitch diameter (Dp) = Mean diameter (Dm) 10.3 Lead = Pitch × Number of starts 10.4 Height of screw thread = 0,866 × Pitch (P) 10.5 Depth of screw thread = 0,613 × Pitch (P) Lead 10.6 Helix angle: Tan θ = π  Dm 10.7 Leading angle = 90° ‒ (Helix angle + Clearance angle) 10.8 Following angle = 90° + (Helix angle ‒ Clearance angle) 10.9 DP = DN – (0,866 x P) Copyright reserved Please turn over

Downloaded from hlayiso.com Mechanical Technology: Fitting and Machining 6 DBE/2023 SC/NSC 11. PYTHAGORAS' THEOREM AND TRIGONOMETRY r y ϴ x y 11.1 Sin θ  r x 11.2 Cos θ  r y 11.3 Tan θ  x 11.4 r 2  x2  y2 Copyright reserved