After spending about 25 hours working on this floor pan, I finally wrapped up the replacement. Why so long you ask for an area that is really not visible? Besides the fact that I'm pretty anal, I'm using this to learn. I decided to treat it like it needed to be as close to perfect as possible.
This was a great learning ground as I mentioned before because it was in such poor shape. I ran into further issues with the support beam that is to the right of the floor pan in the photos, and had to remove it/cut it out. I had accidentally welded it to the floor metal in spots, plus the metal under that support needed to go, so I just cut it all out and replaced the floor pan metal under it.
I have also just purchased the Swag OffRoad Finger Press Brake so that I can make my own support to replace the boogered up one, since new is not available. Updates on that once I get it.
I did learn several things that I was able to apply during the process that helped me and made a better end result. Much of this stuff has probably been written about, but no one seems to really cover it all in their videos which I've looked at extensively, so I thought I'd share. Use with caution, this is my own experience.
1
. Weld on the visible side. Try to do your spot welding from the visible side if you have the option. The back side of the welds is often not evenly penetrated and makes for an ugly final product. Even if you use a backer for the welds, it is rough.
2.
Use a backer for the welds. I found a magnetic copper spot weld backer device that has been VERY handy in doing all these spot welds on some very thin (and in many places
too thin) material. This little device has saved countless hours and saved my sanity! This little thing is genius, and with the good magnet and thumb screw, gets pretty tight on the back of your weld area.
When the weld DOES blow through, and it will at times, it is no longer a stress inducing moment. Now, I just shrug and keep spot welding away with the backer firmly in place absorbing the heat and making a quick project of filling in the gap that was just created. Just be sure to stop if you reach beyond the edge of the backer. At that point, stop, cool down the weld, grind down the mess but leave a good solid base to continue the weld on, and start again after you move the back to cover the weak area.
(I'm not affiliated with any of these products, just passing this on:
https://www.amazon.com/gp/product/B000VHZHBO?tag=ihco-20)
3.
Air grinders and Roloc are your friend - I've been able to be much more precise with my grinding when using a 2" Roloc disc on my air tool grinder vs using an electric with a 4" or larger, thick, zirc disc. I was able to grind down just the spot welds themselves to make the flush without losing a bunch of base metal. The smaller lighter air tool and a fresh 3M 2" Green Corps disc (
https://www.amazon.com/3M-01396-Green-Corps-Roloc/dp/B00HSCLM6E?tag=ihco-20) works really well. I do notice that once the outer 3mm of the edge wears down, it is much harder to target the correct area. I then use the slightly worn discs to cut down on all the main spot weld bulk, and switch out to a new disc to do the final detail grinding of the last 1/2mm to get it to blend in.
I did some cleanup of the finished metal with some 2" fiber type "Roloc" discs. I went from a coarse fiber disc down to a medium fiber disc, but really stopped there as the medium did some good, but body fill, primer and paint will hide most of these imperfections.
4.
The weld process -weld, cool, tap (or tap, cool), grind. I found that it was helpful to do the spot weld, grab a damp rag and cool down the sheet metal around the weld (and inevitably the weld itself), and then using a body hammer and dolly, tap the weld a couple times to release the stress. It may be better to tap then cool, but I was trying to minimize warping and get it cooled quickly. I would then grind only after doing a series of welds so that I could concentrate on one process at a time. i would jump around to weld in different areas in order to be able to use the backer without other welds being in the way of getting the backer flat (and if you are not cooling the welds, in order to avoid too much heat soak in the same area).
5.
Hammer and dollying - I didn't do much of this, but the floor needed a lot of it. I did some but the body man will probably do more. The condition of the floor pan itself left a lot of little waves and divots in the final product. I could spend a lot of time on this part but left it for the body man to make quick work of if he felt it needs it.
6.
Filling small imperfections. When I had small divots or canyons as you would call them, in between areas that had spot welds but could not grind flat due to a lack of material, or just a flaw on the front or back side, I was trying to put a spot weld on that divot and then grind it down. Often enough, since I could not easily locate it on the other side of the panel to put a backer, I'd burn through. But, I had an epiphany and started to drill tiny holes where the imperfections were. This allowed me to get a full penetration spot weld where the weak area was, and it allowed me to easily place the backer on the back side (always on the back side, since I'd already drilled the hole), which improved the process even more since, as I said above, you want to always weld on the presentation side if you can help it.
8. Butt clamps are very helpful - I was recommended this type of butt clamp, and they work pretty well. It requires about an 1/16" gap for the blade of the clamp to poke through, but they tighten down well and make using dissimilar thickness metal very easy to line up. (
https://www.amazon.com/gp/product/B00YF5F9A2/?tag=ihco-20)
