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Step 1
Observe the relationship between electrode size and metal thickness. A thicker base metal will require more penetration for an effective weld and a thicker electrode.
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Step 2
Set the amperage to the recommended setting for your specific application. Most new welding machines have a chart permanently attached to them showing amperage settings for common combinations of electrodes and base metal thicknesses.
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Step 3
Estimate the initial amperage selection upon electrode size. Once the electrode has been selected, the correct amperage may be estimated at one amp per thousandth of an inch of the electrode's diameter. Thus, an electrode ¼ inch thick would require 250 amps (¼ = 250/1000).
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Step 4
Use one pass for a thin base metal. The average welder at home should have a welding machine in the standard 225 to 300 amp range that will allow metal of up to ¼ inch thickness to be welded in a single pass.
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Step 5
Make multiple passes for a thicker base metal. In practice, even professionals use multiple passes for metal thicker than ¼ inch rather than using more than 300 amps. This is primarily because a welding torch will be able to weld continuously below a certain amperage but will need to cool off periodically at higher amperage.
