Metalwork Paper 1 Questions and Answers - KCSE 2021 Past Papers

1. Gains for studying metal work:
   
   1. Acquisition of knowledge.
   2. Acquisition of skills in the area, which acts as the foundation for further practices or training in metal work.                                                                                          (2 x 1) 
2. Two types of prices:
   1. Retail prices - price which the consumer is charged for every item bought.
   2. Wholesale price - price charged for items bought in large quantities.
                    Accept others like buying price and selling                                            (2 x 1) 

(2marks) 

(2marks)

1. Importance of following the correct procedure;
   
   • To avoid accidents.
   • To ensure the work is done correctly
   • Time management
   • Organization of                                                                                             (1 x 1)
2. Precautions taken when lifting:
   
   • Bending the knees while keeping the back straight.                                    (2 x 1)

(1 mark)

(2 marks)

1.  Use of marking agents.
   • During marking, there is need for the marks made on the metals to be clear in order to enable cutting to the correct and accurate size. Marking agents are therefor used to make the lines and marks on metals to be more clear.
     Accept others like the period when the marks should remain visible (2 x 1)
2. Examples of marking agents.
   
   1. Copper sulphate solution.
   2. Chalk.                                                                                                   (Any 2 x 1⁄2)

(2 marks)

 (1 mark)

1.  Procedure of checking flatness:
   • Wipe off any dirt, or oil from the surfaces of both the straight edge to be used and the surface to be tested.
   • Test the surface diagonally, lengthwise and widthwise.
   • Check for any gaps against a source of light.                                       (3 x 1) 
2.  
   1. Datum is a fixed point, line, edge or surface from which measurements are made.
   2. To minimize the parallax error.
      • The tip of the scriber must be properly sharpened.
      • The scriber should be fitted at an angle (preferably 60°) so that its tip gets into contact with the edge of the rule.
      • The edge used in scribing should be held firmly.
      • Avoid excessive pressure on the scriber                                         (3 x 1)

(3 marks)

(3 marks)

 Reasons for blade breakage.

1. Excessive tensioning.
2. Insufficient tensioning.
3. Stroke out of cutting line.
4. Blade jamming in the cut slot.
5. Broken teeth.
6. Excessive speed                                                                                          Any 3 x 1) 

1.  A creasing iron:
   
   
   
2. Uses of a creasing iron.
   
   1. Making angular bends.
   2. Supports the curved surface when closing the edge.                                       (2 x 1⁄2)
3. To separate countersunk rivet.
   
   • Centre punch the counter sunk head.
   • Drill out the head.
   • Punch out the rivet.                                                                                            (3 x 1) 

(2 marks)

(1 mark)

(3 marks)

1. Reason for:
   
   1. Cooling brazed joint in air rather than water:
      
      • Stress in the joint can cause cracks if the cooling is done using water.
      • The joint losses ductility
   2. Packing the work with firebrick.
      
      • To avoid heat loss/insulating heat.                                                    (2 x 1) 
2.  
   1. Reason for manipulating the torch:
      • To give the required fusion of both edges being welded.
   2. Reason for 'cracking' the equipment:
      
      • To clear any dust or other foreign matters in the valve nozzle.
   3. Reason for using flux:
      For cleaning the joint. (Accept any other correct response)                     (3 x 1) 

(2 marks)

(3 marks)

(4 marks)

Explanation of terms.

1. Lower critical point - is the temperature at which steel starts to change its molecular build up, making it possible to alter the final property.
2. Upper critical point - is the point where the molecular change in steel ends. It is the point at which the critical boundaries of steel start breaking down
3. Critical range -  temperature between the two critical points.
                                                                                                                                 (3 x 1)

(3 marks)

1. Two reasons for upsetting a bar prior to bending:
   • Stops the metal from cracking around the bend.
   • The shape of the cross-section is maintained.
   • The structural strength of the material is maintained.                                    (2 x 1½)

(3 marks)

1.  
   1. Advantages of parallel shank drills.
      
      • Cheaper than taper shank drills.
      • Can be used in a wide range of drilling machine, hand and power operated. (2 x 1)
   2. Advantages of taper shank drills.
      
      • Positive drive is given by the shank, no drill slipping.
      • More accurate than a chuck fitting.
      • Quicker to assemble than a parallel shank drill.                 Any (2 x 1)
2.  
         
   Drift is used when removing the chuck to fit a shank drill, sleeve or socket. 
   Sketch      (2 x 1) 
   Any two labels   (2 x 1) 
   Use        (1 x 1) 
3.  
   

2 marks

2 marks

5 marks

4 marks
2 marks

1. SOLUTION
     
                                                                                                                                 2x2
2.  
   
                                                                                                                         Rod - 1
                                                                                                                         Movement - 1
                                                                                                                         Workpiece - 1
3.  
   1. Reasons for testing a welded joint.
      
      • To determine the strength of the joint.
      • To determine the quality of the joint (skill of the worker).
      • To determine the properties of the parent metal.                             (Any 2 x 1) 
   2. Three methods of testing a welded joint.                                   
      • Visual inspection - Remove the slag and inspect for correct fusion, penetration and lack of porosity.
      • Fluid penetrant → clean the surface with a file until it is dead smooth. Apply the fluid. Clean the excess fluid. If there is a flaw, the dye will show.
      • Application of load→ apply the testing load and note how the joint behaves.
                                                                            Accept any other point (3 x 2) 

4 marks

(3 marks)

(2 marks)

(6 marks)

1. The piping effect:
   
2.   
   1. To eliminate piping effect.
      
      • Hammer the bar to form square shape.
      • Hammar to form an octagonal shape.
      • Continue hammering to obtain round shape.
      • Continue hammering to form the taper                                                      (4 x 1)
   2. Difference in the use of a cold chisel and a hot chisel.
      
                                                                                                                             (3 x 2) 
3. Required length.
   лd = 3.14 x mean diam.                                  - 1 mark
   Mean diam:                                                     - 1 mark
   12+ (18 -12) = 12 + 3 = 5
                2
   :. Required length = 3.142 x 15 = 47.1 mm    - 1 mark

(2 marks)

(4 marks)

(6 marks)

(3 marks)

1. Beaded edges are used for:
   
   1. Stiffening the rims of metal articles.
   2. Making the article safe to use.
   3. For aesthetics (For the article to look nice)                                                      (3 x 1) 
2. Procedure for making the beaded edge
   1. Mark out the allowance - 2½D - where D is the diameter of the wire tobe used in folding).
   2. Bend the allowance art right angles along the marked line using folding bars 
      
      
      
3.  
   
   
   
4. How to solder a seam joint:
   
   1. Clean the area to be soldered 
   2. Clean, heat and tin the soldering iron.
   3. Apply drops of solder along the edge of the seam.
   4. Return to the starting point and solder to the far end. Clean the joint.

(3 marks)

(2½marks)
(2½marks)

(3 marks)

(4 marks)