Page 172 - CITS - Fitter Trade Pactical - Volume - 2

FITTER - CITS

EXERCISE 50 : Setting of arc welding machine for
welding

Objectives

At the end of this exercise you shall be able to
• set the arc-welding plant
• set the current according to the size of electrode
• strike and maintain the arc by the scratching and tapping method.

Striking an arc is a basic operation in arc welding. It will occur every time the welding is to be started.
It is an essential basic skill to learn in arc welding.

Setting of arc-welding plant (Fig 1)

Fig 1

Check the working of power source for the welding machine.
Remember electricity is a good servant but a bad master.
Call an electrician for solving any electrical problems.
Connect the welding cables with the welding machines.

Ensure that the cable connections are clean, dry, tight and are attached to the proper terminals of
the machine.
Attach tightly the earth cable with the welding table at the proper place.

Keep the electrode-holder at a safe place.
If the machine is on DC power, connect the cables in correct POLARITY.
Setting a welding current
Set the welding current as per the diameter of the electrode to be used. (Table 1)

Select the electrode as per the thickness of the metal to be welded or as recommended. (Table 1)
Use alternative electrodes of nearest size in the case of non availability of the exact size of electrodes.
The electrodes diameter should not be more than the thickness of the metal to be welded.

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