Page 173 - CITS - Fitter Trade Pactical - Volume - 2

FITTER - CITS

Striking and maintaining an arc
Scratching method (Fig 2)

Fig 2

Hold the electrode about 25mm above the job-piece at one end, perpendicular to the surface.
Bring the welding screen in front of your eyes.
Ensure safety apparel is worn.
Table 1
Plate Electrode Current

Thickness Size mm Range
in mm (approx.) (amperes)
1.6 1.6 40-60
2.5 2.5 50-80
4.0 3.2 90-130
6.0 4.0 120-170
8.0 5.0 180-270
25.0 6.0 300-400
Strike the arc by dragging the electrode quickly and softly across the welding job, using wrist movement only.

Withdraw the electrode approximately 6mm from the surface for a few seconds, and then lower it to (approx) 4mm
distance.
If the arc has been properly struck, a burst of light with a steady sharp crackling sound will be
produced.
Tapping method (Fig 3)
Strike the arc by moving the electrode down to touch the job surface lightly.

Move the electrode slowly up, approximately 6mm for a few seconds, and then lower it to approx. 4mm from the
surface.
The tapping method is generally recommended as it does not produce pit marks on the job surface.

Fig 3

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CITS : C G & M - Fitter - Exercise 50