OK, so here goes. If you got questions just ask.
So I'm assuming you don't have completely destroyed doors, like no tears in the sheet metal or completely folded over. Bent, creased curved is what I started with.
Tools and stuff:
4x rivet gun with plenishing hammer
Sturdy solid saw horse, about the height needed to prop the door open horizontally.
A length of angle iron, probably 1.5x1.5x.125, and just short enough to fit one side in the inside groove where the bulb seal would go.
A bigass piece of flatbar, 6x.5x some length long enough to also prop the door about horizontal. This will be part of the strong back to keep things from bouncing around.
A gravel driveway, or some very solid surface to absorb impact.
Hammer and dolly set.
Sorry I don't have pictures right now but I'll do my best.
Let's assume you have a concave bent door (where it has been pushed outward), with a bend about midline horizontal inward, and a crunched forward corner, as well as a large horizontal crease.
The first thing to remember is that the steel has stretched, and we will basically be shrinking this steel back together. I like to visualize sheet metal as a kind of very thin rigid clay.
You can mash it together and stretch it apart.
We will tackle the large concave bend first.
The side flanges will have poked out, so start by balancing the lower edge of the door against the saw horse, and find the peak of the bend on both ends. Lay your angle iron on the bend and press upon it (even sit on it) concentrating on the ends.
The middle sheet is flexible and most of the rigidity comes from the braked ends. As you press down, the front and back edge will bow in or out.
Get the door fairly flat(ish) then address the flanges with the plenishing hammer to return them to 90 degree angles. The door will pop back to a bent shape, but not as much. Repeat the process until you have diminished returns, and you'll find its pretty darn flat. Its easy to overdo this and bend the whole thing the other direction, so use little moves once its getting close.
You may need to use a large dead blow to knock the center of the panel a bit flatter, but be careful not to make a big dent the other direction. Use lots of small strong blows.
Next is the bent corner.
Prop the door up with an edge of your angle iron under it, resting on the saw horse, and the edge tucked into where the bulb seal would sit. This will be your hammer guide.
Note that it arches high towards where your inward bend is at. This is where you will work first. Use the plenishing hammer to smoothly apply blows back and forth over the arched section, against the edge of the angle iron below. You'll start to see immediate results, with the outside edge bowing in or out. You'd like to encourage it to bow outwards, so if its not going that way, hammer that edge a bit outwards first to give it a start in the right direction. If you let it bend inwards its a lot more work to accurately bend it straight again, so don't do that.
As you hammer the edge back to a 90 degree angle, the bow will form again. Like the first step, you need to repeat the process a few times until diminishing returns.
Now for the crease.
Use the bigass bar to place it under the crease, (inwards or outwards crease, doesn't really matter)
The bar will transfer the energy into the ground, backing blows from your dolly hammer or plenishing hammer. I highly recommended the plenishing hammer because I'd guess several thousand strokes are necessary to get it right (for all these operations)
Be sure you're not supporting the weight of the door only on that bar. The bar should just be there to resist the blows, and the saw horse to support the door. Otherwise you'll end up creating a large bullseye in the middle where youve been hammering at.
Anyway work back and forth on the crease, moving your bar with you to back the blows. Note that it may cause the metal to oil can if you just use a couple big strikes, if you use hundreds of small ones it tends to shrink the metal more. I haven't had to use a shrinking hammer, disc, or torch yet to remove oil cans when I use a plenishing hammer.
Finally, use the hammer (manual or plenisbing) and dolly,bar,or angle iron to continue to true the corners and faces until you're happy with it. You can over work it, so at some point its best to use a little body skim filler to finish it.
A little skim filler is 100 times better than a giant glob of bondo to fill a bent door flat. It just needs to be geometricly close.
Originally Posted by wunderhut