Tweco FP-235DC - Manual (Page 16)

GROUND CLAMP CONNECTION
Be certain you have a solid ground connection. The ground clamp connection is part of the current circuit. A
poor connection at the ground clamp will result in wasted power and heat. Scrape away any dirt, rust, scale, oil
or paint you may find on the workpiece. Make sure the ground clamp directly touches the metal surface.
SELECTING THE ELECTRODE
Welding electrode is a rod or wire of electrically conductive
metal, coated with a layer of flux. When welding, electrical
current flows between the electrode or "rod" and the
grounded metal workpiece. The intense heat of the arc
between the rod and grounded metal melts the wire and the
flux.
The rod wire joins with the base metal of the workpiece to
form the weld bead. Burning Flux forms a gas shield
around the arc, helping to control the flow of the fusing
metals that form the weld bead.
Type and thickness of the metal and the position of the
workpiece determines the electrode type and the amount of
heat needed to weld (see Figure 4). Heavier and thicker
metals require more heat or amperage.
Although there is no hard and fast rule that determines the
exact rod or heat setting required for any given situation,
you can check the rod requirements by referring to the rod
guide on your welder, then experiment on scrap metal.
HIGH VS. LOW VOLTAGE ELECTRODES
Be sure you have the best electrode for the welding job you are doing. Electrode manufacturers make most
standard welding electrodes in two basic types:
1. Designed to run on welders with High Open Circuit Voltage.
2. Designed to run on welders with Low Open Circuit Voltage.
Most welding is done with Low Open Circuit Voltage AC rods such as E-6013 or E07014 general purpose
rods. See Rod Table. Use rods of 1/16", 5/64" or 3/32" diameter.
High Open Circuit Voltage rods such as 6010, 6011, 7018, etc. will not work with most low power welders of
100 Amps or smaller.
Electrode manufacturers have adopted a uniform marking code for rods. Each electrode is marked with a pre-
fix letter and four numbers. Each of the numbers has particular significance. For example, a commonly used
general purpose electrode is marked E-6013. The E signifies the electrode is for electric arc applications.
The first two digits in the number indicate the minimum tensile strength of the deposited metal, in thousands of
pounds per square inch. In this instance, 60 indicates the melting rod will have a minimum tensile strength of
60,000 p.s.i. The third number indicates the welding position for which the rod is intended. A number 1 indi-
cates it is for use in any position.
Number 2 represents an electrode restricted to welding in horizontal and flat positions. Number 3 represents an
electrode intended for use in a flat position only. The fourth digit shows some specific characteristics of the
electrode such as weld quality, type of current or amount of penetration. For all practical purposes, the fourth
position marking will not affect the rod you would normally purchase.
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Figure 4: Shielded Metal Arc Welding