TEST CODE 01335020 FORM TP 2007107 MAY/JUNE 2007 CARIBBEAN EXAMINATIONS COUNCIL SECONDARY EDUCATION CERTIFICATE EXAMINATION MECHANICAL ENGINEERING TECHNOLOGY Paper 02 - Technical Proficiency 2 -y hours ^ 09 MAY 2007 (a.m.) ^ GENERAL DIRECTIONS: 1. This paper consists of THREE sections. You MUST answer FIVE questions. SECTION A: SECTION B: SECTION C: You must answer the COMPULSORY question from this section. You must answer THREE questions from this section. You must answer ONE question from this section. 2. In addition to the 2 y hours, you are allowed 10 minutes to read through the paper. Writing MAY begin during the 10-minute period. 3. Use sketches when necessary to support your answers. 4. Silent electronic calculators may be used. DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO 01335020/F 2007 Copyright 2006 Caribbean Examinations Council. All rights reserved.
This paper is divided into THREE sections - A, B and C. You MUST answer the question from Section A, THREE questions from Section B and ONE question from Section C. This paper contains metric dimensions only. You should work your answers in the metric system. SECTION A You are allowed to use freehand sketches or rule-assisted sketches to answer this question which is based on Module B8 of the syllabus - Engineering Design. The question is worth 40 marks. You are advised NOT to spend more than 50 minutes on this question, 1. Figure 1 shows the configuration of a drilling jig which is to be used to clamp and guide a drill to make a 5 mm diameter hole in pieces of 25 mm diameter pipe. The frame of the jig is made of two pieces of mild steel bars (vertical and horizontal supports) joined together at right angles. For each operation the piece of pipe must be firmly clamped to the horizontal support by the movable jaw in order to drill the hole. A bushing is to be fixed to the movable jaw to guide the drill and prevent it from drifting off to the side of the pipe. The movable jaw is to be operated by a quick-locking and upward-releasing mechanism to allow the easy loading and removal of the pipe from the jig. A removable stop guide is put in place to locate the position of the hole to be drilled. The jig, when installed, is firmly attached to the base of the drilling machine table. Complete the design of the drilling jig, showing clearly the following: (a) (b) (c) (d) (e) A method of joining the vertical and horizontal supports The locking mechanism used to secure the pipe for drilling A bushing for guiding the drill during the drilling process The mechanism in place for lifting the movable jaw each time the lock is released A method of securing the stop guide to the frame (f) The frame of the jig attached to the machine table Total 40 marks
Figure 1
MOVEMENT OF DRILL
- 4 - SECTION B You MUST answer any THREE questions from this section. EACH question is worth 20 marks. 2. (a) Figure 2 indicates a threaded hole in a component. The hole was threaded using M10 X 1.50 mm taps. While carrying out the threading operation a tap broke in the hole and this had to be removed before the job could be completed. Figure 2 How do you determine the tap drill for the hole? List the steps of procedure to be followed to reduce the risk of tap breakage while threading the hole in the component. (iii) Explain a method of removing the broken tap. (b) With the aid of sketches list TWO types of cold chisels used in the workshop. ( 6 marks) (iii) With the aid of sketches explain the use of EACH type of chisel named in (b) above. List TWO precautions that should be observed while using a chisel in the workshop. 1
Figure 3 shows a template that is to be made from a piece of mild steel 3 mm thick by 130 mm long by 100 mm wide. The material is prepared for marking out. Figure 3 (a) List the steps of procedure for marking out the template. Name the tools to be used in the process at (a) above. ( 9 marks) (b) Outline the procedure for cutting out the slot A. (c) Name the tools to be used in (b) above. ( 3 marks) (d) (e) State TW0 precautions that should be observed while marking out sheet metal to ensure accuracy is maintained. State TWO safety precautions that should be observed while cutting out slot A at (b) above.
Figure 4 shows a component that is to be produced on the centre lathe from a piece of mild steel stock 32 mm diameter by 105 mm long. 2x45 DIA30 2x45 Figure 4 (a) With the aid of sketches, list in sequence the operations for making the component. ( 6 marks) (b) List the tools to be used in the procedure at (a). ( 3 marks) (c) List the steps of procedure required to produce the knurled section of the component in (a). (d) State TWO precautions to be observed while producing the knurl at (c). (e) (f) Calculate the spindle speed that is to be used to produce the section marked A on the figure if the cutting speed of the material is 30 m/min. ( 3 marks) State TWO safety precautions that should be observed while working on the centre lathe.
6 nini GROOVED SEAM 5 mm HEM 6 mm LAP AND SOLDER Figure 5 Figure 5 above shows a funnel to be made from 26 gauge galvanised iron. The top of the funnel has a 5 mm hem. The edges of the funnel are secured by a 6 mm grooved seam while the edges of the spout are joined by a soldered lap joint. (a) Make a well-proportioned labelled sketch of the development of the top of the funnel and the spout to indicate the following allowances: Hem Grooved seam (iii) Lap joint ( 6 marks) (b) List the steps of procedure to sweat solder the spout to the top of the funnel. ( 5 marks) (c) List the steps of procedure for producing the folded and grooved seam. ( 5 marks) (d) How is the size of a tinman s snip determined? ( lmark) State ONE method of producing small holes in tinplate. ( 1 m ark) (e) State TWO safety precautions that should be observed when working with sheet metal.
Figure 6 shows a component with a slot that is to be produced on the vertical milling machine. Figure 6 Sketch and name TWO cutting tools that could be used to produce the slot List the steps of procedure for producing the slot. ( 7 marks) (iii) List FOUR factors that could negatively affect the life of a cutting tool. What is the primary purpose of the dividing head that is used in gear-cutting operations on the milling machine? ( 1 mark ) Calculate simple indexing for the following number of divisions: 31, 25, 64 using the Browne and Sharpe plates having the following hole circles. Plate 1 15, 16, 17, 18, 19, 20 Plate 2 21,22,23,24,25,26 Plate 3 27, 28, 29, 30, 31, 32 ( 3 marks) (iii) State ONE safety precaution to be observed while using the milling machine. ( 1 mark)
SECTION C You MUST answer any ONE question from this section. EACH question is worth 20 marks. EITHER (a) An oxyacetylene torch was lit and a sooty flame was produced. Sketch and name the sooty flame. State the reason for the sooty particles. ( 3 m arks) (b) Copy the table below in your answer booklet and complete the welding and brazing columns to match the factor column. Factors Welding Brazing 1. Filler rod material 2. Type of flame carburizing 3. Fusion of work pieces ( 5 marks) (c) (d) (e) Two pieces of 15 mm diameter steel bars are to be welded end to end using the oxyacetylene process. With the aid of sketches, list the steps of procedure to be followed to ensure strength and dimensional accuracy of the finished product. ( 6 marks) Explain the procedure of lighting the oxyacetylene torch and adjusting it to create an oxidising flame after both valves on the cylinders have been opened. State TWO safety precautions to be observed when using oxyacetylene welding equipment.
-10- OR (a) (b) (c) (d) At the beginning of an electric arc welding operation, there was no arc when the tip of the electrode was scratched on the workpiece. State TWO possible reasons why the arc did not occur. Two pieces of 20 mm diameter steel bars are to be welded end to end using the electric arc process. With the aid of sketches, list the steps of procedure to be followed to ensure strength and dimensional accuracy of the finished product. ( 6 marks) List TWO pieces of safety equipment commonly used in the arc welding process. With the aid of a sketch or sketches, illustrate the set-up to perform an arc welding process using reverse polarity, and identify the position of the following: (iii) Work Ground connection Direction of current (iv) Electrode (e) With the aid of sketches, explain the TWO methods of starting an arc. (f) State TWO functions of the coating on the arc welding electrode.
Figure 7 Figure 7 shows a special form cutter that was machined from high-carbon steel. For this cutter to work effectively it must be hardened and tempered. (a) Give the approximate carbon content of such a steel. State the minimum temperature to which the steel should be heated for hardening. (iii) List the steps of procedure to harden the tool. ( 3 marks) (b) (iv) (iii) State THREE changes that occur to a material when it is tempered. ( 3 marks) Explain the difference between thermoplastics and thermosetting plastics. Name ONE thermoplastic and ONE thermosetting plastic material. State ONE use of any ONE of the plastic materials named in (b) above. ( 5 marks) (c) Figure 8 shows a draw spike that is to be produced from a piece of 8 mm diameter mild steel. With the aid of sketches list the steps of procedure for producing the eye at A drawing down the point at B. ( 7 marks)
Name TWO friction and TWO antifriction bearings. With the aid of sketches show the application of ONE friction and ONE antifriction bearing. B C D Figure 9 (iii) Figure 9 shows the cross-section of a bearing. Name the parts labelled A, B, C, D. With the aid of sketches explain how gears can be used to reduce speed while maintaining the same direction in a mechanism. Indicate the driven gears. Show by sketches how rotary motion can be changed to lateral motion. State TWO properties of lubricants. END OF TEST 6l335020/F 2007