Figure 8-14.Torch position at the end of the swing when the
Figure 8-15.Forming a molten puddle with a GTA torch.
rapidly swing the electrode end of the torch down to
within 1/8 of an inch of the work surface. The high-fre-
quency arc will then jump the gap between the electrode
and the plate, establishing the arc. Figure 8-14 shows
the torch position at the time the arc strikes.
If you are using a dc machine, hold the torch in the
same position, but touch the plate to start the arc. When
the arc is struck withdraw the electrode so it is about
1/8 of an inch above the plate.
To stop the arc, quickly swing the electrode back to
the horizontal position. If the machine has a foot pedal,
gradually decrease the current before stopping the arc.
In the following paragraphs the different types of
joints and the procedures used to weld them is discussed.
BUTT JOINTS. After you strike the arc, hold the
torch at a 90-degree angle to the workpiece surface, and
Figure 8-16.Addition of filler metal in the flat position.
with small circular motions, as shown in figure 8-15,
form a molten puddle. After you form the molten puddle,
hold the torch at a 75-degree angle to the work surface
and move it slowly and steadily along the joint at a speed
that produces a bead of uniform width. Move the torch
slowly enough to keep the puddle bright and fluid. No
oscillating or other movement of the torch is necessary
except the steady forward movement.
When you must use a filler metal, form the molten
puddle as described previously. When the puddle be-
comes bright and fluid, you should move the arc to the
rear of the puddle and add the filler metal by quickly
touching the rod to the front edge of the puddle. Hold
the rod at about a 15-degree angle from the work.
Because the electrode is pointing toward the filler metal
or pushing it, it is known as the push angle. Remove the