the base metal, and then slowly raise it a short
distance. If you raise the electrode too quickly, you
will lose the arc. If you raise it too slowly, the
electrode will freeze or stick to the base metal. If
this happens, you can usually free the electrode by
giving it a quick, sidewise twist. If you cannot free
the electrode in this way, remove the holder from
the electrode or stop the machine. Then chip off
the electrode with a chisel, to free it from the base
metal.
CAUTION
Figure 10-8.--Striking or brushing method of starting the arc.
NEVER REMOVE YOUR
HELMET OR THE SHIELD FROM
To start the arc by the striking or brushing
YOUR EYES AS LONG AS THERE IS
method, bring the end of the electrode down to the
A N Y POSSIBILITY THAT THE
work in a continuous motion that describes the arc
ELECTRODE WILL ARC.
of a circle. In other words, strike your arc in the
same manner that you would strike a wooden
match. As soon as the electrode touches the base
After the arc is struck, particles of metal melt
metal, check the downward motion and raise the
off the end of the electrode and are fed into the
electrode to make the arc. The distance between
molten crater of the base metal. The length of the
the electrode and the base metal should be about
electrode is thus gradually shortened. Unless you
equal to the diameter of the electrode. You can tell
keep moving the electrode closer to the base metal,
when the distance is right by the sharp, cracking
the length of the arc will increase. If the electrode
sound the arc will make. Figure 10-8 shows the
is fed down to the plate and along the surface at a
striking or brushing method of starting the arc.
constant rate, a bead of metal will be deposited or
welded on to the surface of the base metal. Before
To start the arc by the tapping method, hold the
advancing the arc, hold it for a short time at the
electrode at right angles to the work, as shown in
starting point to ensure good fusion and to build up
figure 10-9. To establish the arc, lower the
the bead slightly. Good arc welding depends upon
electrode and tap it or bounce it on the surface of
good control of the motion of the electrode down to
and along the surface of the base metal.
BREAKING THE ARC
There are two correct methods for breaking an
arc. The most commonly used method is to shorten
the arc, and then quickly move the electrode
sidewise out of the crater. The other method is to
hold the electrode stationary until the crater is
filled, and then slowly withdraw the electrode.
REESTABLISHING THE ARC
When it is necessary to reestablish the arc (as
when the length of weld requires the use of more
than one electrode), the crater must be cleaned
before striking the arc. Strike the tip of the new
electrode at the forward (cold) end of the crater.
Figure 10-9.--Tapping method of starting the arc.
10-12