WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
The arc is established by lowering the electrode, tapping or
bouncing it on the work surface, then slowly raising it a short
distance, approximately the diameter of the electrode. When the
proper length of arc is obtained, a sharp crackling sound can be
heard.
(4) If the electrode is withdrawn too slowly, with either arc
starting method described above, it will stick or freeze to the
plate or base metal.
If this occurs, the electrode can usually
be freed by a quick sideways wrist motion to snap the end of the
electrode from the plate.
When this method fails, remove the
electrode holder from the electrode or stop the welding machine
and free the electrode with a light chisel blow.
WARNING
If the electrode becomes frozen to the base metal
during the process of starting the arc, all work to
free the electrode when the current is on should be
done with the face shield pulled down over the eyes.
(5) Some electrodes, known as contact electrodes, are normally
struck by holding them in contact with the work.
These
electrodes are used mostly by private industry rather by the Army
in the field.
(6) Two procedures, described in the following subparagraphs,
are used to break the arc.
(a) In manual welding, when the electrode is changed and the
weld is to be continued from the crater, the arc is shortened and
the electrode moved quickly sideways out of the crater. When the
arc is re-established it is started at the forward or cold end of
the crater, moved backward over the crater, then forward again to
continue the weld. The crater is also filled by this procedure.
(b) In semiautomatic welding, where filling or partial filling
of the crater is required, the electrode is held stationary for a
time sufficient to fill the crater and then is gradually
withdrawn until the arc breaks.
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