Lincoln Electric SP-135T, Operator'S Manual

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B-7
LEARNING TO WELD
B-7
LEARNING TO WELD
No one can learn to weld simply by reading about it.
Skill comes only with practice. The following pages
will help the inexperienced operator to understand
welding and develop this skill. For more detailed infor-
mation, order a copy of
“
New Lessons in Arc Welding
”
listed at the end of this manual.
THE ARC-WELDING CIRCUIT
The operator
’
s knowledge of arc welding must go
beyond the arc itself. The operator must know how to
control the arc, and this requires a knowledge of the
welding circuit and the equipment that provides the
electric current used in the arc. Figure B.7 illustrates
the welding circuit for a typical welding machine. The
circuit begins where the gun cable is attached to the
welding machine. Current flows through the gun
cable, gun, and contact tip, to the wire and across the
arc. On the work side of the arc, current flows through
the base metal to the work cable and back to the
welding machine. This circuit must be complete for the
current to flow.
This machine
’
s welding circuit has a voltage output of
32 volts DC maximum. This voltage is quite low and is
only present when the gun triggers depressed.
To weld, the work clamp must be tightly connected to
clean base metal. Remove paint, rust, dirt or oil as
necessary and connect the work clamp as close as
possible to the area you wish to weld. This helps pre-
vent current from going through an unwanted path.
Avoid allowing the welding circuit to pass through
hinges, bearings, electronic components, or similar
devices that can be damaged. See Figure B.8. Always
disconnect electrical devices before welding upon
them.
FIGURE B.8
Fumes and slag generated from
Innershield type electrodes recom-
mended for use with this welding
machine can be toxic.
• Avoid contact with eyes and skin.
• Do not take internally.
• Keep out of reach of children.
• Follow all safety precautions
found in this operating manual.
The gun and cable assembly is held by the operator
who guides the automatically fed wire along the joint,
maintaining a contact tip to work distance of about 3/8
to 1/2 inch (10
–
12 mm) This is called electrical stick-
out. This electrical stickout (ESO) must be properly
maintained by the operator. The electric arc is made
in the gap between the work and the tip end of a small
diameter wire. When the power source is properly set,
the arc gap is maintained automatically.
Arc welding is a manual skill requiring a steady hand,
good physical condition, and good eyesight. The oper-
ator controls the welding arc, and, therefore, the quali-
ty of the weld made.
THE SELF-SHIELDED FCAW WELDING
ARC
Figure B.9 illustrates the action taking place in the self
shielded FCAW (Innershield) welding arc. It closely
resembles what is actually seen while welding.
FIGURE B.9
SP-135T
Electronic Components
Hinges
Bearings
WARNING
Burning of core materials
inside wire electrode
results in shield of gas.
Arc Stream
Cored Wire
Protective Slag
Weld Metal