KCSE 2011 Metalwork Paper 1 Questions with Marking Scheme

METAL WORK (445) 

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

1.        
   1. State four causes of accidents when using a cold chisel.(2 marks)
   2. State the minimum entry requirement for each of the following courses:
      1. artisan;
      2. diploma;
      3. craft.
         (1 ¹/₂ marks)
2.            
   1. Outline the procedure of reading a micrometer.(2 marks)
   2. State four uses of a scribing block.(2 marks)
3.                
   1. Use sketches to show the length of each of the following rivets:
      1. countersunk head;
      2. round head;
      3. raised countersunk.(3 marks)
   2. Use labelled sketches to show two uses of a template.(3 marks)
4. Name a suitable material and state the property that makes it appropriate for making each of the following:
   1. twist drill bit;
   2. livet;
   3. head of ball pein hammer;
   4. kitchen knife blade.(4 marks)
5.                 
   1. With reference to filing explain:
      1. the term pinning;
      2. how pinning is prevented;
      3. how pinning is treated.(3 marks)
   2.            
      1. Use a labelled sketch to show the safe edge of a file.
      2. State the function of the safe edge of a file.(2 marks)
6.               
   1. State two advantages of a leg vice over engineer's vice.(2 marks)
   2. Outline the procedure of locating the centre of a round bar using the centre head and the rule of a combination set. (2 marks)
7.           
   1. State two forms in which filler metal for brazing is manufactured.(1 mark)
   2. Give one reason for manufacturing filler metals in different forms.(1 mark)
8.          
   1. Explain the term welding.(1 mark)
   2. State two advantages of rightward welding over leftward welding.(2 marks)
9. Describe the process of oil blacking as applied to metal finishing.(3 marks)
10. Figure 1 shows an oblique drawing of a block.
    
    Sketch in third angle projection the three orthographic views of the block. (5 ¹/₂ marks)

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

11. Figure 2 shows orthographic views of a machined block drawn in third angle projection,
    
    On the grid paper provided, draw the isometric view of the block taking X as the lowest point. Show three leading dimensions.(15 marks)
12.      
    1. Figure 3 shows a link to be made of 6 mm thick mild steel. Outline the procedure of making the link naming all the tools required in each step.(6 marks)
        
    2.    
       1. Sketch a pop rivet and label its parts.
       2. List three steps involved in preparing work pieces for pop riveting.
       3. With the aid of sketches, outline the procedure of pop riveting.(9 marks)
13.             
    1. Sketch an anvil and label three parts.(3 ¹/₂ marks)
    2. Figure 4 shows a portion of an arm bar made from a 6.0 mm square mild steel rod.
       
       
       1. Determine the length of the material required to form the bend labelled l.
       2. With the aid of sketches, outline the procedure of making the arm bar (11¹/₂ marks)
14.               
    1. Use sketches to show the difference between a lap joint and a flush lap joint.(2 marks)
    2. Outline the procedure of sweating as applied to soft soldering and name all the tools and materials required in each step.(8 marks)
    3. Give four safety precautions to be observed when soldering.(2 marks)
    4. State three reasons why copper is preferred in making head of a soldering iron.(3 marks)
15.             
    1. Sketch a gas welding torch and:
       1. label five parts;
       2. state three precautions to be observed when handling it.(7 ¹/₂ marks)
    2.            
       1. Use labelled sketches to show the three types of gas welding flames.
       2. Explain how each of the flames is obtained.(7 ¹/₂ marks)

MARKING SCHEME

1.      
   1. CAUSES OF ACCIDENTS
      1. Failure to hold chisel firmly
      2. Failure to use goggles
      3. Using chisel with mushroomed head
      4. Using blunt chisel
      5. Failure to hold work piece firmly
      6. Grieared chisel
         Any 4 x ¹/₂ = 2 marks
   2. ENTRY REQUIREMENT
      1. ARTISAN KCPE
      2. DIPLOMA KCSE (C Plain) or Craft certificate
      3. CRAFT KCSE (D Plain) of Artisan
         3 x ¹/₂=1 ¹/₂marks
2.          
   1. READING MICROMETER
      1. Read the whole number on barrel/sleeve
      2. Read complete subdivision on barrel
      3. Read number on thimble before datum line
      4. Read extra divisions coinciding with datum line
      5. Finding the centre of the round bar.
         4 x ¹/₂= 2 marks
   2. SCRIBING BLOCK
      1. Marking out
      2. Testing parallelism
      3. Testing alignment
      4. Testing roundness/concentricity
         4 x ¹/₂= 2 marks
3.              
   1.    
      1.      
         
      2.    
         
      3.    
          
         3x 1 = 3 marks
   2. Marking + appropriate sketch
      Checking + sketch
      Guiding + sketch
      Any 3 x 1= 2 marks
4.           
   1. Twist drill    -     HSS/HCS   -   Hardness and wear resistance
   2. Rivet   -    MS, Alminium, Brass, Copper   -   Malleability ductility
   3. Hammer head    -   Medium Carbon Steel    -   Toughness/hardness
   4. Knife blade   -   Stainless steel   -   Non-corrosive/hardness/easy to cold work
      8 x ¹/₂ = 4 marks
5.             
   1.           
      1. Clogging of a file by metal chips
      2. Applying chalk on the surface
      3. Cleaning using a file card or wire brush
         3 x 1= 3 marks
   2.            
        
      Allows filing one surface of a shoulder or inner corner
6.           
   1. LEG VICE
      1. Enhanced rigidity hence withstands heavy blows
      2. Capable of opening more hence holds wider work piece
      3. Withstands very high temperatures
         Any 2 x 1= 2 marks
   2.          
      1. Slide the rule through the slot in the centre head and lock. Hold the centre head against the end of the bar
      2. Scribe a line across the end of the bar
      3. Rotate the bar and scribe another line to obtain a centre of intersection/bar
         4 x ¹/₂= 2 marks.
7.         
   1. Forms:
      1. Rod, wire, strip, powder
         Any 2 x ¹/₂= 1 mark
   2. REASON:
      To cater for
      1. thickness of material being brazed
      2. the design of the joint
      3. method of heating the metal
         Any 1 x 1= 1 mark
8.           
   1. WELDING
      The process of joining metals by heating them to melt and fusing together.
   2. RIGHTWARD WELDING
      1. Deeper penetration and faster
      2. Rate of cooling is reduced hence better results
      3. Less gas is used
      4. No berel is required for steels up to 8.0 mm thus less filler metal required/used..
         Any 2 x 1= 2 marks
9. OIL BLACKING
   1. Clean the surface
   2. Heat to red hot
   3. Dip in clean thick oil
   4. Heat again to burn excess oil
   5. Allow to cool
   6. Clean the surface
      6 x ¹/₂= 3 marks
10. SOLUTION
    
    9 faces x 1/2= 4 1/2
    Hidden details = 1/2
    3rd angle projection = 1/2
    Total= 5 ¹/₂ marks
11.     
    
12.            
    1.           
       1. Scribe the centre line using a scriber
       2. Step off the 75mm hole centres using dividers
       3. Dot punch hole centres using hammer and punch
       4. Scribe 18mm radius using dividers and rule
       5. Scribe 25mm radius using rule and dividers
       6. Join 18mm and 25mm radii tangentially using rule and scriber
       7. Drills holes Ø 18 and Ø 25 using a drill bit.
       8. Cut along the outline using a hacksaw
       9. File the outline smooth using a file.
          6 x 1= 6 marks
       10. POP-RIVET
           
       11. STEPS
           • Mark and drill the plates
           • Debur the plates
           • Align the holes
             3 x ¹/₂= 2 ¹/₂ marks
       12. Insert the rivets into the work piece and grip the pin with the rivet gun.
           Press the gun to pull the pin causing the head to expand the body.
           Continue pressing the gun until the pin breaks off.
           3 x 1= 3 marks
           Any 2 sketches x 1=2 marks
13.          
    1. ANVIL
       
    2.          
       1. LENGTH OF MATERIAL
          Inner radius   18
          Outer radius 18 + 918 + 3
          Mean radius ⁴²/₂ = 21
          Length of curvature = ^2Πr/₄
          (2 x ²²/₇ x 21) x ¹/₄
          =33mm
       2. RADIUSED BEND
          • Obtain a suitable template/jig for Ø 36 or R18
          • Mark the area to be bent
          • Heat the area to be bent
          • Clamp work piece against the jig
          • Bend to shape.
            5 x ¹/₂= 2 ¹/₂ marks
            
            
            TWISTING
          • Heat the area to be twisted
          • Grip firmly in the vice one end of area to be twisted
          • Hold the other end with tongs or wrench
          • Twist the bar 90° or 180°
            4 x ¹/₂=2 marks
            
            Total = 3
            
            BENDING
          • Mark section to be bent
          • Heat the section to be bent
          • Hold in the vice
          • Bend at 90°
            
14.           
    1.     
       
    2. PROCEDURE:
       1. Clean the surface to be soldered, with abrasive cloth
       2. Clean the soldering bit with a file
       3. Tin the soldering bit.
          • heat the soldering bit until it is brown
          • apply flux to the point
          • add solder to the point
       4. Tin the surfaces separately i.e. apply flux
          • heat
          •  apply solder
       5. Put the surfaces to be joined together and press firmly.
       6. Heat the joint using any suitable heat source e.g. soldering iron,
       7. Gas torch or blow lamp etc; until the solder melts.
       8. Let the joint cool while still applying pressure
       9. Clean the joint to remove any excess flux.
          8 x 1= 8 marks
    3. SAFETY RULES
       1. Keep the hot iron away from the body.
       2. Do not put the hot soldering iron on a wooden bench.
       3. Liquid flux is corrosive and must be kept away from eyes.
       4. Do not touch a newly soldered joint - The joint may still be hot
          4 x ¹/₂ = 2 marks
    4.         
       1. Copper conducts heat very well. 
       2. Copper retains heat for a long time.
       3. Copper picks up solder very easily.
          3 x 1- 3 marks
15.              
    1. WELDING TORCH
       
       SAFETY PRECAUTIONS
       • Ensure that the nozzle seat and threads are free from any foreign materials.
       • Nozzle should only be cleaned with tip cleaner
       • Never use nozzle to hold or push the work piece
       • Avoid knocking nozzle against hard surfaces
         Any 3 x 1= 3 marks
    2. GAS WELDING FLAMES
       
       1.      
               
       2.         
          • Neutral Flame has equal quantities of oxygen and acetylene
          • Carburising flame has more acetylene gas than oxygen
          • Oxiding flame has more oxygen than acetylene gas