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+ Every bead is a sentence, and the machine writes clean if you hand it a clean page. Most guys chase dials — amps, wire speed, voltage. I'll tell you the same thing I told my apprentice Dan over a structural job last spring: The weld tells you more than the settings ever will. Read the bead and you're reading the truth.
Shut the hood, let it cool to a dull gray, then run a gloved finger down the crown. A good MIG bead has oyster-shell ripples — even, tight, stacked like weathered shingles. Too flat and glassy means you were cold and fast; the toes never tied in. Too gutted — a valley down the middle — and you've got a cold-lap pocket waiting to crack. The ripple is the metal settling as the puddle freezes, and it always tells the truth about travel speed.
-The heat-affected zone reads off in temper colors, exactly like a blacksmith's blade. Around a clean weld you want straw bleeding into light blue — that's a bead that cooled slow and stayed out of trouble. Catch oxide gray or that iridescent rainbow burn and you cooked the joint: grain grew coarse, hardness fell off, and under load that's where it parts. Chromoly and stainless get pickier than mild — one shade past straw and you've burned the corrosion resistance out of the tube.
-The two lines where the weld meets the base metal — the toes — are where every joint lives or dies. Feather the toe into the parent plate, no sharp notch, no undercut. Then tie each pass into the previous one's crown, overlapping about a third. The look you're after is the stacked dime — overlapping caps, even width, no crater at the stop. That crater's a stress raiser; a crater crack will find you at three in the morning after the part goes in.