The Twin-Carbon Arc Torch - Craftsman 113.201892 Owner's Manual

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THUMB KNOB
CONNECTTO
GROUND AND
SCREWS ]ELECTRODE
CABL.£SOF
EL,1ECTRODE TIPS A.C. W)E.LD[R
Figure !
Work ordinarily done with a gas welding torch is possible
with the twin-carbon arc torch connected to an A.C, welder.
The carbon-arc flame is similar to the flame of a gas weld;
ing torch in that it provides heat by radiation, rather than
by direct arc between work and electrode. This flame heat
greatly widens the scope of Work possible with the arc
weldei" for brazing, soldering, wetding of non-ferrous metals
and localized heating for bending; forging and hardening.
The arc torch (fig.: 1)Consists of an insulated handle with
two projecting carbon eiectr0de holders, one of which is ad-
justable to permit striking and breaking an arc at the carbon
tips. A thumb knob on the handle performs the adjustment
and operates a shut-off switch bui|t into the handle; There
are nO valves or gauges that:, require fine adjustment as
with an 0xyacetylene t0rch. The same proteCtiveequipment
used for Ordinary arc welding is used: when Operating the
carbon'.arc:torch; ........
A wide selection Of flame heats may be had by varying
the current and size of the carbon electrodes. Although the
actua| temperature of the arc remains :the Same for any
current setting, the vo|ume of transferable heat increases
with an increase in amperage. However; amperages in
excess of thosegiven below will only Causeshort carbon llfe.
1/4-in. Carbons................ 30
tO
40 amperes
5/16-in. carbonsL ........ ...40 to 65 amperes
3/8-1n. carbonS. ........... 65 to 90 amperes
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i Figure 2
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RC TORCH
To pre|0are the torch for use, connect its two cables to the
ground and electrode cables of the welding machine.
Grounding of the work is not necessary as the operation of
the arc flame is entirely independent. With the thumb knob
or_the handle in the "off" posltion, insert two 3tS-inch car-
bon electrodes in the holders and damp in place at approxi-
mately one-half their length (fig. 2). Do not clamp them
on or near the ends opposite from the arc as this will cause
overheating of the carbons. When tightening the clamping
screws, be careful not to apply too much pressure on the
carbons, as they are very brittle and break easily. Use only
enough pressure to hold them firmly in place, tf the tips
of the carbons do not line up with each other, an adiustment
may be made by turning the longest of the electrode holders
sllghfly; too much turning will loosen it, and make it neces-
sary to disassemble the torch to again tighten it properly.
Do not make any turning adjustments with the sliding holder
as this would spoil the contact tension in the switch.
To strike the arc, turn on the welding machine and set it for
approximately 70 amperes. Lower the welding helmet and
hold the torch up to silhouette it against the light of a win-
dow. Slowly move the thumb knob forward until contact
is made between the tips of the carbons, This will start the
arc. Then immediately move the knob back to increase the
gap between the carbons. The actua} distance can be deter-
minect with a little practice. When the carbon s are too close
the arc flame will have a sharp crackling noise. As the
distance between the carbons is increased, the crackling
will change to a soft purring sound which indicates the best
arc flame. There are two heat zones and the small inner
zone is by far the hottest, having an estimated temperature
of 9000 degrees Fahrenheit (fig. 3).
The shape of the flame greatly influences the way in which
it must be used. Forexample: on beveled work the torch
should be held parallel to the groove so the flame will reach
the bottom (fig. 4). If held at right angles to the groove, the
flame straddles the groove and the heat will not reach the
bottom (fig. 5). Filler rods, as for gas welding, must be used
on joints of this type.
The soft, bushy flame is pressureless and has no tendency
to blow the molten metal. This is a distinct advantage when
welding thin sheet metal. Joints on light material should be
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CORRECT FLAME POSITION
Figure 4
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INCORRECT FLAME POSITION
Figure 5
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