FITTING AND TURNING
NQF LEVEL 4
NOVEMBER EXAMINATION
This question paper consists of 10 pages.
TIME: 3 HOURS
MARKS: 100
INSTRUCTIONS AND INFORMATION
1. Answer ALL the questions.
2. Read ALL the questions carefully.
3. Number the answers according to the numbering system used in this question paper.
4. Write neatly and legibly.
QUESTION 1
1.1 Various options are given as possible answers to the following questions. Choose the answer and write only the letter (A–D) next to the question number (1.1.1–1.1.10) in the ANSWER BOOK.
1.1.1 What safety measures must a maintenance electrician follow prior to working on electrical equipment?
A Remove all the fuses from the equipment.
B Lock out and tag all electrical switches on the relevant distribution board.
C Check the belt tension.
D Instruct all fellow workers not to turn on the switch.
1.1.2 The most important method of ensuring operator safety is by …
A encouraging all the workers to dress neatly.
B providing the workers with the company rules and disciplinary procedures.
C conducting mandatory safety training on a regular basis and alerting the
workers to unsafe acts and conditions.
D ensuring that all ablution facilities are kept clean with sufficient tissue paper.
1.1.3 What is the main purpose of a preventative maintenance programme?
A To ensure that the spare parts kept in the stores may be timeously utilised
B To keep the engineering maintenance team occupied
C To test the readiness of the standby equipment
D To ensure that plants and equipment continue running as efficiently as possible
1.1.4 How should we dispose of chemical waste?
A It should be flushed down the storm drainage systems.
B In accordance with health and safety regulations.
C In a dump yard and covered with sand or sawdust.
D Into the nearest dam or river.
1.1.5 What is the main cause of accidents in a workshop?
A Machining of hard materials
B Human error
C Insufficient sunlight
D Staff being dissatisfied with their salaries
1.1.6 An efficient machine guard should …
A restrict access to the danger zone.
B allow workers to clean the machine while it is in operation.
C permit the maintenance team to open it while the machine is in operation.
D provide minimum protection to the operator of the machine.
1.1.7 With respect to the validity rule, readings are …
A taken at the top and bottom points of a shaft.
B taken at three different points.
C taken at all four cardinal points.
D recorded at every second cardinal point.
1.1.8 The soft foot condition that occurs on machines can be described as …
A distortion of the frame of the machine.
B misalignment of the pulleys of a machine.
C a condition caused by wet floors.
D leakage of oil from the machine gearbox.
1.1.9 For repairs to be done accurately and to eliminate malfunctioning of components:
A Provide workers with the correct safety equipment
B Implement correct reporting and preventative procedures
C Allow incompetent and unqualified staff to repair machines
D Ignore the manufacturer’s specifications and schedules
1.1.10 The used oil in a factory must be …
A stored in large sealed drums and dumped into the sea.
B kept in suitable containers or reservoirs for the oil recycling companies to collect.
C disposed of into the water drains.
D treated as hazardous waste and released into the sewer system.
(10 × 1) (10)
1.2 Minor and major repairs are categories for maintaining equipment in a manufacturing environment.
1.2.1 Distinguish between major repairs and minor repairs. (2 × 1) (2)
1.2.2 Give ONE example of a minor repair and ONE example of a major repair that could be carried out on a centrifugal pump. (2 × 1) (2)
1.3 Why is standby equipment necessary in a plant? (2)
1.4 The procurement of the correct spares before a plant is shut down is an important feature in the planning department in factories.
Indicate TWO advantages of this process. (2 × 1) (2)
1.5 Give TWO reasons why all equipment and machinery are accompanied by a manual that contains the manufacturer’s specifications. (2 × 1) (2)
[20]
QUESTION 2
2.1 Indicate whether the following statements are TRUE or FALSE. Choose the answer and write only 'true' or 'false' next to the question number (2.1.1–2.1.10) in the ANSWER BOOK.
2.1.1 The pressure relief valve regulates the flow of oil in a hydraulic system.
2.1.2 Hydraulic energy is stored in the accumulator of a hydraulic system.
2.1.3 The pump in a hydraulic system compresses the oil, thus increasing the pressure in the system.
2.1.4 Pneumatic systems are not suitable for use in fire risk areas.
2.1.5 Hydraulic systems operate under much higher pressures than pneumatic systems.
2.1.6 Pneumatic systems are much faster than hydraulic systems.
2.1.7 Linear actuators are used on hydraulic and pneumatic systems.
2.1.8 Pneumatic systems are not suitable for applications under high temperatures.
2.1.9 Pneumatic systems are self-lubricating.
2.1.10 The landing gear of aircraft is activated by hydraulic systems.
(10 × 1) (10)
2.2 The service unit is an essential device that is installed on pneumatic lines.
2.2.1 List the THREE components of a service unit. (3)
2.2.2 Briefly describe the function of each component. (3 × 1) (3)
2.3 Why would you consider it essential to relieve the pressure in a hydraulic system before installing or servicing a hydraulic valve? (2)
2.4 Though hydraulic and pneumatic systems share many characteristics in common, there are some key differences. Compare a hydraulic system with a pneumatic system with reference to the following criteria:
2.4.1 Installation costs
2.4.2 The medium used in each system (2 x 1) (2)
[20]
QUESTION 3
3.1 Choose a description from COLUMN B that matches an item in COLUMN A. Write only the letter (A–J) next to the question number (3.1.1–3.1.10) in the ANSWER BOOK.
COLUMN A COLUMN B
3.1.1 The left-hand knife tool A is used to support the work piece when the t
ailstock is set over for taper turning
3.1.2 The parting tool B is available to fit most standard size holes
3.1.3 Gang mandrels C is used so that a work piece can be faced up
to the centre hole
3.1.4 The right-hand knife tool D is used when machining a work piece from
right to left
3.1.5 The round-nosed tool E are parallel and are used for holding a number
of similar work pieces at the same time
3.1.6 A ball centre F is used for cutting off work pieces on the
centre lathe
3.1.7 The plain mandrel G is used when machining a work piece from
left to right
3.1.8 Lathe steadies H is used to machine round grooves in a work piece
3.1.9 A driving plate I support long slender shafts and prevent them
from bending during the machining process
3.1.10 A half centre J fits onto the spindle nose and drives the
carrier when turning work between centres (10)
3.2 A long slender shaft is being turned in the lathe. After the first cut, the shaft was measured with an outside micrometre and it was discovered that the diameter at the right end of the shaft was smaller than the diameter at the left end of the shaft. The cutting tool was found to be in a good condition and the work piece was secure between centres.
3.2.1 Examine the above situation carefully and give a reason for this fault. (2)
3.2.2 Briefly explain how this machining fault can be rectified. (2)
3.3 The cutting speed for cast iron is given as 25 m/min. The diameter of the cast iron rod is 40 mm. Calculate the time it would take to make one cut over the length of 250 mm on the cast iron rod, if the automatic feed of the cutting tool is 0,5 mm/revolution. (3)
Use the formulae: S = Pi X D X N and
L = f X N X t
3.4 Leaving the chuck key in the chuck of the centre lathe is a common habit amongst students in the machine shop. Why would you regard leaving the chuck key in the chuck an unsafe act? (1)
3.5 Sipho was machining the outside diameter of a 65 mm shaft and realised that the work piece was chattering. The work piece was securely gripped in a four-jaw chuck.
On inspection, the cutting tool was found to be in good condition and appropriately sharpened. Identify TWO other reasons that could cause chattering on a work piece. (2x1) (2)
[20]
QUESTION 4
4.1 Complete the following sentences by filling in the missing word. Write only the word next to the question number (4.1.1–4.1.10) in the ANSWER BOOK.
4.1.1 The … trips, trip the automatic feed at pre-set positions.
4.1.2 The … drives and holds the cutters on a universal milling machine.
4.1.3 A … drill is used to machine slots and grooves on a work piece.
4.1.4 A … cutter is used for milling screw head slots or narrow grooves.
4.1.5 A … cutter is used for machining concave grooves or slots in a work piece.
4.1.6 When determining the cutting speed on the milling machine, the operator needs to know the … and the RPM of the cutter.
4.1.7 A … vice may be used to securely clamp a work piece on the milling machine table.
4.1.8 The milling machine operator must always use safety … to protect his/her eyes from flying chips.
4.1.9 A … cutter is used for machining the bottom of T-slots for machine tables.
4.1.10 When the number of divisions to be machined on a work piece cannot be obtained by using the simple indexing method … indexing can be used.
(10 × 1) (10)
4.2 State THREE factors that must be taken into consideration when the feed rate of the table feed for a milling operation has to be determined. (3)
4.3 The clamping of a work piece on the milling machine table is a necessary and important procedure.
State THREE factors that you will take into consideration before deciding on what clamping device to use. (3 × 1) (3)
4.4 Calculate the indexing required for an angle of 55° using a Cincinnati dividing head.
CINCINNATI DIVIDING HEAD
Side 1 25 30 34 37 41 42 43 45
Side 2 47 53 54 57 59 62 66 68
INDEXING = (2)
4.5 Lwandle is working on the milling machine and the cutter gets burnt.
State TWO possible factors that could lead to the cutter getting burnt. (2 × 1) (2)
[20]
QUESTION 5
5.1 Truing and dressing of grinding wheels are necessary procedures to be carried out while performing grinding operations. Differentiate between the terms truing and dressing as applied to grinding wheels. (2 × 1) (2)
5.2 The selection of the correct grinding wheel for a specific workpiece is dependent on a number of factors. State THREE important factors that you would consider before selecting a grinding wheel. (3 × 1) (3)
5.3 Nelisiwe is a turner machinist at a general engineering company and is performing a grinding operation on a block of steel on a horizontal surface grinding machine. She notices that the workpiece is getting discoloured and turning brownish in colour.
Answer the following questions regarding Nelisiwe’s workpiece:
5.3.1 Identify the grinding fault that has occurred. (1)
5.3.2 Give TWO probable causes of this grinding fault. (2)
5.3.3 What remedial action should Nelisiwe take to solve this problem? (2)
[10]
QUESTION 6
6.1 The CNC lathe is a precision machine that is designed for mass production of simple and complex components. What does the abbreviation CNC stand for? (2)
6.2 Once a machining cycle has been worked out, the controller must first check the program by simulation before conducting a trial run on the CNC machine.
State TWO reasons why the controller should first simulate the program. (2)
6.3 Differentiate between incremental dimensioning and absolute dimensioning as applicable to programming on a CNC machine. (2)
6.4 It is important that a CNC operator works safely and pays attention to the Health and Safety Act as well as the manufacturer’s manual.
Why it is important to study the manufacturer’s manual before working on certain specialised CNC machines? (1)
[10]
TOTAL: 100
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