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Metalwork Report

19.0 METAL WORK (445)

The 2010 KCSE examinations for Metalwork consisted of two papers namely Paper 1 (theory) and Paper 2
(Practical Project). The theory was worth 60% while practical was worth 40% of the final mark.

19.1 CANDIDATES GENERAL PERFORMANCE

The table below shows candidates overall performance for the period 2005, 2008, 2009 and 2010.
 

Year Paper Candidature Maximum
Score
Mean Score
 
Standard
Deviation
2005 1
2
Overall
311
 
60
40
100
23.40
34.90
57.74
9.60
3.24
12.00
2008 1
2
Overall
89
 
60
40
100
23.62
35.62
59.24
6.96
4.57
9.38
2009 1
2
Overall
231
 
60
40
100
25.38
35.34
58.74
9.09
3.38
13.32
2010 1
2
Overall
222
 
60
40
100
22.60
15.25
37.70
9.09
4.32
12.58


From the above table, the following observations can be made.
19.1.1 The mean score for the year 2010 Is the lowest compared to the means for the other years shown on the table. This is an indication that the paper was poorly performed in 2010 compared to previous years.
19.1.2 The number of candidates taking metal work decreased in 2010 compared to other years except 2008 when the number was 89.

19.2 PAPER 1 (445/1)

The questions which were reported to have been poorly responded to will be analysed with a view to pointing out candidates weaknesses and propose suggestions on some remedial measures that would be taken in order to improve performance in future. The questions for discussions include 1,4,5, 10. ll&15 in Paper 1(445/1).

Question 1
(a) State four safety precautions to be observed when using a feller gauge
(b) Distinguish between:
(i) gross pay and net pay
(ii) change and balance

Weaknesses

Many candidates saw the two transactions as similar.

Comment
The item of concern here is lb (ii) which required the candidates to distinguish between the commonly used terminologies of change and balance.

Expected Responses

(a) SAFETY PROCEDURES

Wipe the blade clean before use.

Oil the blades fold into case after use

Don't force blades into gaps.

Avoid over tightening locking screw.

Don't expose to heat or corrosive substances

Do not detach blade from set.

(b) (i) Gross pay is all payment due before any deductions while net pay is
payment due after all deductions.
(ii) Change is transaction involving exchange of different denominations of equal amount while
balance is the amount due after purchase of good or payment of services.
Change is transaction involving exchange of different denominations of equal amounts, while balance is due after payment of goods or services.

Advice
Practical demonstration of the two concepts would help in comprehension. The terms change and balance are
used in everyday life, but incorrectly.

Question 4
Use labeled sketch a to show the:
(a) Length of an outside caliper
(b) Setting of an inside caliper using a rule.

Weaknesses

Whereas sketching the two measuring instruments is not a challenge, labeling of its features was key weakness.
Expected Responses
OUTSIDE CALIPERS


Advice

In teaching of these instruments, emphasis should be put on identifying and naming their key features.

Practical use through designed projects would enhance mastery of these key features.

Question 5
Explain the effect of clearance angle when chipping with a chisel.

Weaknesses

Candidates did not understand what clearance angle is, consequently explaining its effect proved challenging.

Expected Responses

(a) CHIPPING ANGLE
Too large clearance angle makes tool point to ‘dig' into the work while too small clearance angle tend to cut thin material or slapping.

(b) TWIST DRILL WITH UNEQUAL LIPS

Excessive wear

Rough hole and out of round

Overheating

Breakage of drill

Oversize hole

Advice
Concept of various tool angles need to be illustrated and practically demonstrated.

Question 10
Figure 2 shows an isometric drawing of a block.
Sketch in third angle projection, the orthographic views of the block. (5½ marks)

Weaknesses

Perception of the three orthographic views of a multi-shaped block is an area of concern.

Interpretation of l angle and 3 angle projection is of concern too.

Expected Responses

In addition to clearly illustrating the connections of 1 angle and 3 projection, it is essential that students are regularly taken through drawing of orthographic views of a block from isometric or oblique and also from orthographic to pictorial (isometric or oblique). Use of physical shaped blocks would help. Proportionality of the drawings should be emphasized.
 

Advice

Question 11
On the isometric grid paper, provided, thaw the isometric view of the block taking X as the lowest end.

Weaknesses

Interpreting concept of lowest point, in this case point X, was ignored.

Despite being a compulsory question, majority of the candidates did not attempt the question.

Converting multishaped orthographic views to pictorial view is a key weakness.

Expected Responses

Advice

Though only two views are given in this item, students should be encouraged to visualize or consider constructing the missing view taking into account the stated angle of projection.

With all the three orthographic views in perspective, construction of the pictorial block would be cross- checked and ascertained.

Special emphasis should be put on lowest point, while use of grid paper would ensure proportionality is obtained.

Teaching of construction of isometric circles is necessary.

Question 15
(a) With aid of sketches, show and name two types of soldering bits.
(b) Outline the procedure of:
(i) Marking opener
(ii) Shaping opener
(iii) Making opener resistant to wear.
(iv) Finishing opener by oil blocking
Comment
Concern here is on questions 15(b).

Weaknesses

Candidates had a challenge of conceptualizing the sequential task of making the opener. The item itself has four key steps of making the opener, but candidates did not realize that each point stated has key details. Indeed this was the task.
 

 


Expected Responses

(a) SOLDERING BITS
The hatchet type soldering bit
Cable


The electric soldering bit
(b) (i) MARKING
Curved end:

OUT THE OPENER
Establish the datum edge
Mark the round end
Mark R II and dot punch
Slot:
Mouth:
Mark the two centres and dot punch
Mark and scribe curved ends
Joint the tangents and dot punch
Mark centre and punch
Mark the mouth strip width (5 mm)
Curvatures:

(ii) SHAPING
Curved end:
Prepare template Align, mark and dot punch.
Drill 0 10 holit
Cut and remove excess mobrals
File to shape the curved end.
Slot:
Mouth:
Drill 0 10 hols on both ends
Chain drill
Chise out
File to size and shape
Drill 012 holej
Cut out
File strip to width and shape
Curvatures: Make relief cuts Chise/cut
File to shape

(iii) RESISTANT TO WEAR
Heat to cherry red and dip in carbon rich solution Quench in water/oil
The straight soldering bit

(iv) OIL BLACKING
Clean to obtain smooth surface
Heat to red hot
Coat with clean oil
Heat and let cool
Wipe to clean

Advice to Teachers

In all project work, students should be encouraged to write step by step procedure of performing a task.

Broadly each project involves marking, shaping and finishing. Each of these tasks would have detailed steps which need to be stated in point form and in a logical sequence.


 

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