Finally got gas and solid wire instead of flux core wire for my welder, as several people on here recommended. The difference is amazing. Thanks, very much, to all the remote welding coaches (there are no local welding coaches here) -- starting with those in this old but still very helpful thread: Got a welding coach
I was able to make a welding mistake that I'd never been able to do before -- weld a "ropey" bead on sheet metal. Now I know pro and experienced welders wouldn't consider poor penetration to be anything to get excited about, but _always_ before I have blown so many holes in sheet metal that it looked like it was infested with worms. All the advice received here, including dumping the flux core wire for thin stuff, made it possible for me to get to the other side of this problem that has plagued me for years. Thanks!
Attached is a photo of a holey weld from the time of the welding coach thread and a photo of the latest rope.
Here's a tip for anyone who has the Harbor Freight "Dual MiG 151" welder. The manual doesn't tell you, but you have to reverse the wire feed wheel to use wire smaller than the "0.9 mm" flux core that comes with the welder. Just take out the 2 philips head screws near the bottom of the attached photo, slide the cover off the wheel (there's a bushing in that plastic cover), pull the wheel off the drive axel and reverse it, screw the cover back on.
The attached photo shows a close-up of the wheel with its twin grooves. After I switched from the flux core wire to some solid .024" wire, it wouldn't feed. I fiddled with the feed tension for a while and then finally looked at the wheel with a magnifying glass and saw the two different sized grooves.
[Edited to add:]
Almost forgot, that welder can take the bigger spools of wire in spite of the manual saying its capacity is 4" spools. Just use an empty small spool for a bushing. Cut one of the flanges of the small spool down to the size of the hole through the large spool and put 'em together. See attached photo.