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The GMAW flat (S-class) is your first qualifying position—and one of the most commonly failed because it seems “easy.” In this video, Kevin Roy shows exactly how to pass it: control your arc and travel speed, manage starts/stops, and—most importantly—ride the wave, not the puddle to get penetration.

What you’ll learn

• Test plan & setup: Two starts/stops; square side → bevel side workflow
• “Ride the wave” principle: Stay ahead of the puddle to ensure penetration
• Backer bar advantage: Use the entire bar to preheat, stabilize, and avoid low ends
• Root technique:
  • Small, hot first pass; move quickly; don’t encroach on the bevel side
  • On the second root pass, start way back, use the material to heat the backer & coupon
• Edge control: Watch the edge melt away, then move—no dwelling
• Restart strategy for cold starts (MIG):
  • Do not start at the crater and go backward
  • Start behind the stop where the puddle solidified, let the arc settle, tie in, small pause, go
• Interpass cleaning: Wire-wheel between passes to remove silica/dirt
• Capping & profile: Keep edges maintained, avoid excessive width/height; fix undercut/underfill with an extra pass if needed