So since some of you guys are trying to weld some pretty thin sheet metal -- here's something you might FORGET to do in this process….
#1 - your fit up will make or break the whole job. Poor fit = poor welding
#2 - a GOOD welder can deal with sloppier fit - but beginners -- trust the rest of us - spend your time on making your parts FIT CLOSELY.
#3 - Tack your work in the proper order. Yes - there is an order. If you tack the piece in the middle - your corners will pull out of shape…. put too much heat on the corners and your middle will bow etc. So of course there's about a hundred an fifty eight gazillion ways to do things - but I like to tack up the corners first. Then the middle - then in between the corner and the middle.
NOW HERE'S THE PART YOU WILL FORGET - when in the heat of battle (is that a pun?)….. USE YOUR FRIGGIN HAMMER and tap those edges back in to place!
What you'll see is that while the square might still be a square - and still "fit" the square hole (if that's the shape of your patch or whatever) - it will have moved IN AND OUT of that hole so there's still a gap - but the gap has opened off the "flat" -- so you need to massage that back so the pieces are matched up on the same plane. If not - you'll burn thru the high edge.
We're talking MINUTE -- that's MI NUTE -- here -- but remember that if you're working with sheet metal - this is thin stuff to start with. Sheet steel is measured in 1000th of an inch. 18 gauge is .050 -- 19 gauge is .0438 ---- 20 gauge is .0375
If you're "gap" has moved off plane --- 20/1000th --- you're not only going to have a difference in the off plane metal to deal with in your finish work - your gap there is just that much more to try to weld as well. It's these very small things that we "forget" when we're new and we're so focused on just running the torch and all that.
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