KCSE 2015 Metal Paper 1 with Marking Scheme

SECTION A (40 marks)
Answer all questions in this section in the spaces provided.

1.    
   1. Name four career training programmes in metalwork. (2 marks)
   2. Define the term “self employment”. (1 mark)
2.    
   1. Name three types of cold chisels and give one use of each. (3 marks)
   2. List six operations that can be performed on a drilling machine. (3 marks)
3.  
   1. Give two reasons in each case why the following should be avoided in the workshop:
      1. long hair;
      2. long nails. (2 marks)
   2. State four factors to consider in order to obtain strong brazed joints. (2 marks)
4.    
   1. State the use of the following instruments:
      1. vernier protractor;
      2. vernier height gauge. (2 marks)
   2. State the function of the following parts of a micrometer screw gauge:
      1. ratchet;
      2. spindle. (1 mark)
5. Define the following properties of metals giving one example of a metal with the property:
   1. malleability;
   2. toughness;
   3. plasticity. (3 marks)
6.    
   1. State three advantages of oxy-acetylene welding over other methods of welding. (3 marks)
   2. Give two reasons for rounding off the tip of a lathe cutting tool bit. (1 mark)
7.    
   1. With the aid of a labelled sketch, illustrate the hollowing process. (4 marks)
   2. State the use of marking agents and name any two. (2 marks)
8.      
   1. List three tempering techniques used in heat treatment.
   2. Define the term “point of recalescence” as used in heat treatment.
9.    
   1. The diameter of a snap head rivet is 4 mm. Determine the projection allowance required to form the head when riveting. (1 mark)
   2. State the defects caused by each of the following in riveting:
      1. failure to use a rivet set;
      2. too much rivet shank projecting. (2 marks)
10.    
    1. Outline the procedure of bluing as a metal finishing process. (2 marks)
    2. Use sketches to illustrate upsetting as a forging process. (3 marks)

SECTION B (60 marks)
Answer question 11 on the A3 paper provided and any other three questions from this section in the spaces provided. Candidates are advised to spend not more than 25 minutes on question 11.

11. Figure 1 shows an isometric drawing of a block.
    
    Draw the following views full size in first angle projection:
    1. front elevation in the direction of arrow F.E;
    2. end elevation in the direction of arrow E.E;
    3. the plan. (15 marks)
12. Figure 2 shows a drawing of a bench drilling machine.
    
    
    1. Name the parts labelled A, B, C, D, E, F and state one function of each. (6 marks)
    2. Outline three safety precautions to observe when using the machine. (3 marks)
    3. Explain the relationship between the following:
       1. speed and feed;
       2. speed and drill diameter;
       3. feed and material. (6 marks)
13. Figure 3 shows a working drawing of a spanner to be made from a mild steel plate 122 x 42 x 4mm.
    
    Outline the procedure of:
    1. marking the size of spanner; (8 marks)
    2. making the spanner; (5 marks)
    3. case hardening the spanner. (2 marks)
14. Figure 4 shows a component to be produced on a lathe machine.
    
    
    1. Identify the details at:
       1. point A;
       2. point B. (1 mark)
    2. Use labelled sketches to show the set up of the workpiece on the lathe machine to produce:
       1. detail A; (7 marks)
       2. detail B. (7 marks)
15.      
    1. With the aid of sketches, distinguish between square and round hollow tongs. (5 marks)
    2. State four uses of a swage block. (2 marks)
    3. With reference to brazing, outline the procedure of:
       1. lighting the blow pipe; (5 marks)
       2. shutting down the equipment. (3 marks)

MARKING SCHEME

SECTION A
Answer ALL the questions in this section.

1.    
   1. Career training programmes in metal work
      • Welding and Fabrication
      • Refrigeration and Air conditioning
      • Mechanical production
      • Mechanical plant Fitting
        (Any 4 x 1 = 2 marks)
   2. "Self employment" is when an individual starts income generating activities and the profits from the sale are utilised by the individual. (1 marks)
2.    
   1. Types of cold chisels
      • Cross-cut chisel - For cutting narrow square, grooves in metals.
      • Diamond - pointed chisel - for cutting v-shaped grooves in metals.
      • Half-round chisel - for cutting circular grooves in metals.
      • Flat chisel for general purpose.
        (3 x 1 = 3 marks)
   2.    
      • Drilling
      • Counter boring
      • Counter sinking
      • Spot facing
      • Reaming
      • Decorating surfaces
        (= 3 marks)
3.    
   1. Reasons for avoiding
      1. Long hair
         • Can be caught by moving machine parts.
         • Tends to obstruct the worker from seeing the work clearly during working operations.
           (2 x 1 = 1 mark)
      2. Long nails
         • can hurt the fingers and others.
         • make it difficult to handle a work piece.
         • can collect dirt which can be transmitted to food i.e unhygienic.
           (Any 2 x 5 = 1 mark)
   2. Factors to consider in order to obtain strong brazed joints:
      • Clean the parts to be joined.
      • Ensure the joint is well fitting.
      • Use the correct filler metal.
      • Apply sufficient heat i.e. heat to the correct temperature.
      • Clean the joint after brazing to remove any excess materials.
        (= 2 marks)
4.    
   1. Vernier protractor - used for measuring and marking angles/checking angles.
      Vernier height gauge - use for measuring and marking parallel heights.
      (4 x 1 = 2 marks)
   2. Functions of:
      • Ratchet - Ensures the correct pressure when measuring.
      • Spindle - Contains very accurately cut threads which provide accuracy when reading.
        (= 1 mark)
5.    
   1. Malleability is the ability of a metal to be hammered or rolled into thin sheets without cracking. Examples are; mild steel, aluminium, copper, brass, tin, gold, dead mild steel, wrought iron.
      Definition
      Example
   2. Toughness is the ability of metal to resist fracture or deformation when subjected to external forces. Examples are; medium carbon steel, alloy steels.
      Definition
      Example
   3. Plasticity is the property that makes a metal remain deformed or retain the new shape after the load has been removed. Examples are; lead, copper, gold, aluminium.
      Definition
      Example
      (3 marks)
6.    
   1. It can be used to join thin metals.
      • It does not cause change in properties of the material.
      • Due to the slow cooling process the joint is left ductile.
      • The equipment is portable therefore can be used in various and confined places.
      • Initial costs and maintenance are low where the gases are available.
        (Any 3 x 1 = 3 marks)
   2. Reasons for rounded tip of a lathe cutting tool.
      1. To produce a smooth finish
      2. To form an internal curve/groove.
      3. To avoid breakage of the tip of the tool.
         (= 1 mark)
7.    
   1. 
      
      Hollowing on a round block using a blocking hammer.
   2. To enable markings on metal appear more clearly. (1 mark)
      • copper sulphate solution
      • Blue vitiriol
      • Chalk
        (Any 2 x 1 = 1 mark)
8.    
   1.    
      • Open flame heating
      • Hot plate tempering
      • Sand box tempering
   2. Point of recalescence” is the point where temperature remain constant while steel is being heated. (1 marks)
9.    
   1. Projection allowance = 1½D=1½ x 4 = ³/₂ x 4 = 6 mm (1 mark)
   2.      
      1. Failure to use rivet set - Rivet expanded between gap. (1 mark)
      2. Too much rivet shank projecting
         • Rivet bends
         • Mis-shaped head.
           (Any 1 x 1 = 1 mark)
10.    
    1.    
       • Polish the article with an abrasive cloth.
       • Heat the article with a clean flame until a blue colour appears on the surface
       • Dip the article in clean light oil,
       • Wipe with a clean cloth after it has cooled.
         (= 2 marks)
    2.   
       
11. 
    
    Correct angle of projection = 1 mark
    F.E 4 faces@1
    E.E 5 faces 1
    Plan 4 faces 1
    Hidden details
    Total =15 marks
12.    
    1.    
       1. Foot (base) table - It supports the machine and is used for mounting
       2. Chuck - used to hold work
       3. Feed handle - used for feeding the drill but into the hole.
       4. Gear selection levels - used for changing speed
       5. Locking handle - used for locking the head.
       6. Column/pillar - It supports the head.
          = 6 marks
    2.    
       • Clamp the work firmly on the base/foot of the machine
       • Wear/use safety goggles to protect the eyes against flying chips.
       • Hold the drill bit firmly in the machine chuck.
       • Never leave the chuck key on the chuck after use.
       • One person should operate the machine at a time.
       • The speeds should never be changed when the machine is running
         Any 3 x 1 = 3 marks
    3. Relationship between:
       1. Speed and feed - when the speed is high the feed should be low and vise versa.
       2. When the diameter of the drill is small, the speed should be high and if the diameter is large then the speed should be low.
       3. The softer the material the higher the feed and vise versa.
          3 x 2 = 6 marks
          Total 15 marks
13. Marking
    1.    
       1. Determine and file the datum edges flat and square.
       2. Mark the centerline.
       3. Centre punch the two centres
       4. Mark the curvatures R10 & R20.
       5. Mart the opening /hexagon
       6. Mark the tangents
       7. Dot punch the profile
       8. Mark and punch for chain drilling the opening.
          8 x 1 = 8 marks
    2. Making
       • Drill Φ 6.
       • Chain drill the mouth/opening.
       • Cut the profile
       • File to shape
       • Deburr & polish
         5 x 1 = 5 marks
    3. Case hardening
       1. Heat the polished work to cherry red
       2. Dip in casemite compund/carbon rich compound/use carburising flame
       3. Re-heat until the compound melts
       4. Quench in water
          (= 2 marks)
          Total = 15 marks)
14.    
    1. Point A - Taper
       Point B - Diamond knurling
       = 1 mark
    2. 
       
       Label
       • Chuck
       • Work piece
       • Toolbit
       • Compound slide
       • Feed direction
         
         Sketched part
       • Chuck
       • Work piece
       • Toolbit
       • Compound slide
         Labels
         Sketched
         Set up
         = 7 marks
         
         Labelling
       • Chuck
       • Work piece
       • Knurling tool
       • Tailstock
       • Knurling
       • Direction of feed
         
         Sketched parts
       • Chuck
       • Work piece
       • Knurling tool
       • Tail stock
         Total = 15 marks
15.    
    1.  
       
    2. Uses of a swage block
       • Punching
       • Drifting
       • Drawing down
       • Flattening
       • Swaging
       • Holding swages and stakes
         = 2 marks
    3.    
       1. Lighting up
          1. Open acetylene cylinder valve turn.
          2. Open oxygen cylinder valve full turn
          3. Ensure you turn off the needle valves at the torch
          4. Open the acetylene needle valve to set the required working pressure
          5. Close the acetylene needle valve
          6. Open the oxygen needle valve to set the required working pressure.
          7. Close the oxygen needle valve
          8. Open the acetylene needle valve and light the torch.
          9. Increase the acetylene gas until the flame is clear off the soot.
          10. Open the oxygen torch valve and set the required flame.
              = 5 marks
       2. Shutting down
          1. Turn off the acetylene valve at the torch.
          2. Turn off the oxygen valve at the torch.
          3. Turn off the regulator valves each at time.
          4. Turn off the cylinder valve each at time .
          5. Open the torch valves to clear the pressure in the line.
          6. Close the torch valve.
             = 3 marks