A root pass is a fairly common weld that is often used on stick welding exams. According to the AWS D1.1 welding code book, a standard qualification test is 3/8" plate beveled 22 1/2" gap 1/4" with 1/4" thick backing strap. Multiple stick welding passes must be made in order to achieve sufficient penetration and thickness in a gap like this.
How you make those multiple passes will determine whether you can pass a welding test or produce a sufficiently strong weld.
There are two ways to weld a root pass: weaving and stringers. Stringers are straight passes that are stacked alongside each other when the weld joint is particularly wide. The most important thing to remember is to leave gaps wide enough for your electrode. Failing to do that will prevent you from getting sufficient penetration into the weld joint.
While some welding tests will require stringers, Welding Tips and Tricks recommends weaving instead of stringers. Though some welders stand by their stringers, here’s what he has to say, “Weaving allows for a hotter puddle, and is less likely to give you trapped slag, inclusions, cold lap, porosity, etc.”
Weaving requires moving back and forth across the joint and then laying each weld on top of the previous one. This saves you from having to plan ahead for your gaps.
You can learn more about these two stick welding techniques by watching related videos at Welding Tips and Tricks.
Learn More About Stick Welding: Stick Welding Overview and Tips