work without first releasing the trigger
of the brake support by moving the screw in the
to break the arc. Failure to observe this
slotted hole until just enough pressure is applied to
precaution may result in: (1) Loss of
the wire spool to prevent the wire from uncoiling.
the gas shield before the weld pool
(4) Welding set-up. The following data is
intended as a starting point in arriving at the proper
freezes, causing porosity; (2) Too much
wire will extend from the nozzle at the
adjustment of the system for welding an aluminum
j o i n t . It is important to understand that final
end of the weld requiring a clipping
operation before the next weld; (3)
adjustment for a particular joint may vary con-
Extremely high transiet voltages can
siderably from this data depending on the weld
develop which may damage the motor.
position, fit up material thickness, fillet size, etc.
(a) Set the voltage control on the welder to
(5) Welding techniques. After the operator
20 volts.
has found the desired current, voltage, and elec-
t r o d e feed speed settings for a particular ap-
NOTE
plication, it is still necessary to observe some
The open circuit voltage is usually about one to
elementary principles of technique.
two volts higher per 100 amperes of welding
(a) Nozzle spacing. In general, the gas
current than the arc voltage.
nozzle should be held as close to the work as is
(b) L o o s e n t h e p r e s s u r e s c r e w ( 4 ) a n d
practical. In most cases, a distance of
inch to
release the swing arm ( 5 ) to move the idler roll out
inch is satisfactory.
of position. Taking care not to touch the worn piece
(b) Gun angle. T'he best cleaning action is
with the wire, squeeze and hold the weld trigger; at
obtained, and excellent porosity-free welds are
the same time, adjust the gas regulator to give the
made by using a forehand technique. For example,
required gas flow. As a starting point, adjust the gas
a horizontal fillet is best made by the welding gun
flow to 35 cubic feet/hour. An increase or
at an angle of 40 to 50 to the horizontal and
decrease may be required after welding conditions
using a forehand angle of 20 to 25 . A right-
have been established. Reclose the swing arm and
handed operator would then weld from right to left
readjust the pressure screw.
on a horizontal weld.
(c) Cleanness of material. It is essential
(c) Adjust the position of wire so that the
free end protrudes inch to inch beyond the
t h a t aluminum be absolutely clean when it is
end of the nozzle.
welded. To ensure porosity-free welds, a cleaning
operation should immediately precede the welding
(d) Turn the electrode feed speed control to
operation.
Use solvent Fed Spec O-T-634
the maximum setting.
(e) With the electrode near the work, but
(Trichloroethylene, Technical) and then wire brush
not touching, lower the head shield, squeeze the
area to be welded with stainless steel brush. Final
trigger, and bring the electrode into contact with
clean with acetone and let dry.
the work piece to strike an arc.
(d) Wire cleanness. Wire should be clean
and free from oxide, grease, and other foreign
(f) Reduce the electrode feed speed control
material. Do not try to use wire that is not clean.
setting
until the stabbing
ceases
and
the
Wire which is not in use should be kept in a con-
"crackling" sound of the arc just disappears. When
t a i n e r which will protect it from all forms of
the setting of the electrode feed speed control is
reduced, the weld current is reduced.
e. Welding With Stick Electrode. Refer to TM
(g) T O stop the weld, release the trigger and
5-3431-221-15 for instructions on welding with
draw the welding gun away from the work.
stick electrode.
CAUTION
Do not whip the gun away from the
Section Il. OPERATION OF AUXILIARY MATERIAL USED IN
CONJUNCTION WITH THE WELDING SHOP
2-3. Fire Extinguisher
the left front tool box, mounted to the under side of
the cover.
a. Description. The fire extinguisher is the dry
b. Operation.
c h e m i c a l type c h a r g e d w i t h e n e r t g a s u n d e r
(1) Open clamp securing fire extinguisher in
pressure. It is useful for all classes of fires and is
bracket.
safe to use on electrical fires. The chemical is non-
toxic to humans and when used on a fire, emits no
(2) Remove extinguisher from bracket and lift
bottom lever, breaking the parer seal.
toxic by-product. The fire extinguisher is located in
