Spent my day off practicing welds on an old kitchen cart and finally get what those little coin-shaped beads are

That click of realizing the ripple is just frozen metal makes so much sense once you see it happen. I had the same moment a few years back when my dad and I fixed up an old trailer gate with his little stick machine. I figured the neat dime-sized ripples on the original factory welds meant the guy was some kind of artist, and my own beads looked like bird droppings for the first two weekends. What finally helped me was slowing way down and watching the puddle instead of the arc. Once I coud see the molten spot travel and solidify behind the rod, the stack-of-dimes look started showing up on its own. I never got it consistent on vertical joints though, gravity fights you the whole way up. The comparison to timing a busy kitchen line rings true too. My wife bakes for the farmers market and she said the same thing when she tried a bead once, that it is all about reading what the material is doing and adjusting instead of forcing a plan on it. These days I can lay down a bead I am not embarrassed by, but I still knock the slag off and look underneath to judge if it actually held. Pretty on top, ugly underneath has fooled me before.

I'll offer a slightly diffrent take on judging those cart welds. I spent a few years doing maintenace at a machine shop, and my boss always said the prettiest bead means nothing if it's cold rolled onto the surface. He'd hand me a 2 lb ball peen and tell me to tap a suspect weld and listen. A good one rings sharp, a junk one sounds dull. Not scientific, but it caught more than one bad repair on our carts and stands before they failed in service.

Your cart has been getting shoved into ovens, soaked in degreaser, and loaded with sheet pans for who knows how long. If those corner welds have survived all that without cracking at the ends, that tells you more than any stack of dimes ever will. Failures in stuff like that almost always start at a crater where the welder stopped, or a tie-in where one bead meets the next.

I also learned the hard way that heat control in my garage MIG work had nothing to do with cooking instincts. My wife is the cook in the house, and when I tried to explain it as 'like keeping a roux moving' she just laughed at my bird poop beads. Took me a whole spool of .030 wire before my ears stopped ringing after every practice session and my beads stopped sounding dull when I tapped them.

That kitchen line comparison hits home from the other side. I cooked for about six years before I ever struck an arc, and the first time a buddy let me run beads on his shop table I said the exact same thing. You alredy know how it feels when a pan is at temp and you stop second guessing it. Welding was the same for me, my beads got decent the day I quit jabbing at the puddle and just let it ride. One thing I'd add for your scrap practice, grind that mill scale off the angle iron first. My practice beads went from lumpy to smooth the same afternoon I finally hit clean metal.

I'd push back on the tap test advice. I've done that listening trick on welds I knew were good and welds I knew were garbage, and half the time I couldn't tell them apart by sound. The bracket thickness, how it's clamped in, even paint on the joint changes the tone. A dull ring on a chunky weld can just mean the metal is thick and stiff. If you actually want to check somthing, grind a test coupon from the same stock, weld it the same way, and break it in a vise. Ugly bead that tears out the parent metal beats a pretty one that peels off clean every time.

One thing about that cart, it's probaly been through worse than any test you'd give it. Kitchen carts get rammed into stuff, loaded heavy, hosed down every night. If those corner welds have held togehter for years of that, they're fine for what the cart needs. My garage shelf brackets have ugly beads on them and they've carried cast iron pans for a decade. Also your brother-in-law's machine, is it stick or wire feed? That changes what your practice beads should look like, took me a while to figure that out when I started.

Update: tried the tap test on my practice beads from the weekend, the ones I knew were lousy still rang about the same as the decent ones, so I get what the last poster said about tone being unreliable. Grabbed the cart though and one corner weld sounded noticeably duller than the others. Is that a red flag on a commercial cart, or just how it sits in the frame?