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Old 02-17-2012, 10:03 PM
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Quote:
Originally Posted by John68040

Questions:
1. Any tips/things to watch out for there? I'm under the assumption that I'm going to have to alternate and tack it, not running a bead anywhere.
2. Can I flare the edge outwards a hair, then weld and have it end up mostly flat after I grind down the welds? From what I've heard seams like this tend to sink a little from being welded.
3. What can I do to get it as smooth as possible without using filler? I'm planning to use a skim coat of fiberglass over top to finish it up but I'd like to keep it to a minimum.
4. Any tips on lining it up and cutting it to fit properly? I was planning to cut out a template, and trim the panel and car to match so it sits pretty close - leaving a little extra so I can slowly trim it until everything fits closely.
1. Make small tack welds and let them cool naturally. Do not cool them with air or a wet rag. You'll shrink the metal this way. Make your tacks every six inches or so, let cool, then go back and push a tack bead onto your cooled, previous tack bead. I feel the weld with my hand to make sure it's not warm to the touch before making another weld.

2. The seams sink because the metal shrinks. Even if you flare it, you will still get shrinkage. Those aren't big replacement panels with wide open weld runs at the seams, but since you haven't mastered the welder you should plan on some pretty ugly welds that you'll probably have burned in there pretty good. Welding is very difficult to do well initially, and it takes a lot of time and practice to get good at it. I actually find butt welding to be easier than lap welding.

3. Since you've never welded before, you should just plan on having to use filler rather than trying to get a weld so perfect it will require hardly any filler. And I say that because you're just going to have a difficult time getting it to that point, being a novice and all. Keep in mind when you're grinding down your welds, the grinder generates immense heat as well and can further distort the metal if you keep it on one area too long. Don't dwell on any one spot, and jump around alot, letting your welds cool before going back to hit them more. If you can fit a dolly in from the back of the panel, hold it up tight against the back of the weld, then do on-dolly hammer on the weld from the front, this will stretch the metal and you'll actually see the metal start to flex back out. It's exhausting work though.

4. What I've found works really well (and accurately) for me is--if the replacement panel can fit directly on top of/over the old panel--use metal screws and screw it down to the old panel nice and tight so everything lines up well. Then take your cut off wheel and cut right along the edge of the new panel. Unscrew the new panel, continue to remove the old panel if needed, and the new panel will fit right into place and your cut will line up perfectly since the edge of the new panel actually guided the blade. It automatically leaves for a bit of space between the edges of the panels because you don't want your new panel actually touching the original panel if you're doing a butt weld; there needs to be a tiny bit of space between them.
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