school me on door bottom replacement please

[chimp koose]

OK so my door panel bottoms have arrived . Questions to ask. Do i fold the edges over BEFORE I weld or after or a little of both ? I will be able to weld them from the inside of the door , would that be easier as to less grinding to clean up the front face ?The panel is about 7" tall but I only need the bottom 4" . Was thinking it might be better to join it closer to the bottom as it is curving in/downward  at that point and would show less if it pulled in a little . When I did the door to wheelwell panel it was about 4" tall and it pulled in a little bit (weld seam is low)but nothing a litttle swipe with pudding couldnt fix. I welded the wheelwell panel from the outside . Any experienced advice welcomed , I had to buy 2 panels and only need 1 so I guess I can screw up 1 time and still have a second chance but would rather get it right the first time  

[moose]

Cut as little of the old door as possible. You are correct the closer to the edge or a radius as possible will minimize warpage. When I can I will weld from the inside if mig welding in a patch. As you said you can cut down on heat from grinding. Are you planning to butt weld the joint? That is usually the best way. I always weld the patch before setting the overlap to lock the panel edge. That gives a little room for movement as you are welding.

Tim

[idrivejunk]

I could write a booklet full of thoughts on this but am on my lunch break.

Experience says everything Moose said is yep.

During... is my when to fold approach. If a total of 4 passes to fold, pass 1 then tack. Pass two then more tacks. Pass three but err to the loosish side and complete welding. Then crimp that puppy and weld desired edge spots. Trouble is, the overall crown is up in the air until the patch is fully completed.

As I said, several many more thoughts. I have a theory that welding the joint with door upright and inverted is advantageous due to heat rising into the new metal, which being a more consistent thickness should tolerate it better.

My last encounter with this repair, on the F1... was a real wrestling match. Door skin bottoms on high crown designs are a true test of the bodyman in ya. If I can offer any sage advice, it would be to bring the rest of the door to straightened perfect as possible before making a cut.

[chimp koose]

I will butt weld the panel . overlapping would lose the curve. So basically trim for a zero gap if possible and but weld , from the inside as close to the bottom of the door as I can. Fold the edges in a little at a time after each pass of tack welds . Probably better to fix any shape issues before welding any further if they do crop up . Door is actually pretty straight right now . I had the door in a molasses bath for a couple of months and it found rust along the bottom edge . It is crazy how clean the metal gets after the molasses and no distortion from blast media .

[moose]

Another tip, make sure your weld heat is correct to achieve a full penetration weld. one trick I use is to set my heat a bit hot and use a thick copper backer on the out side and make a series of tack welds moving around the panel and make sure to be cool between close tacks.

As you said watch for movement and control/correct as you go.

[chimp koose]

Yup got a copper strip and I will set up the mig with 2 pcs of scrap the same thickness until I get it just right . When I did the 1/4 panel I think I got the weld just right with next to no warpage but I got in a hurry grinding the welds and it puckered inward just a bit . A little swipe of bondo should tune it up as its not too deep , maybe 1/16 at most but I would have to check. Thanks for the help guys ! I think I know what to do but it doesnt hurt to have someone who has done it chime in with the finer details . The door panel might need a little tune up before I cut/weld the patch panel as there are 2 small dents that you cant see but I can just feel them when I pass my hand over the door . I also have to fix the inner door panel at the bottom as the bottom folded edge is rusted /cracked . I should be able to make that panel without too much trouble. I have a tile cutters contour gage that I use for checking panel shape so I will iron out the dents in the door skin before I cut it for the repair panel . If I cut the door off 4" from the bottom I can access most of the welding from the back . Rust only goes 2" up the door in one spot smaller than a playing card but the bottom seam along the reveal is split most of the way across.

[idrivejunk]

Things that come to mind reading replies are first, yessir it is a dance where one missed step can really trip a guy. I have seen everyone struggle on these repairs. Turn your watchful knob to full blast. That being said, second I have these observations:

Zero gap- If you are using TIG, OK yes but I don't know about that method. With MIG, somewhere I picked up on a more official guideline of: Gap one and a half times the thickness of the metal. Plenty of weld heat is important but you have probably welded tubing also and know how important adequate gap is on that. No different, the weld has to have a place to be. For my gap, I go back after I like my first tacks and use a regular plain cutoff wheel in between. To uniform the gap. I get penetration. Not leaving a gap, with MIG... really makes a mess of things. IMHO.

I don't know where the boundary lies between metal work and advanced metal work but the advanced stuff is a huge leap. Planishing is something I learned in recent times. A perfect MIG weld is harder than the surrounding metal and the surrounding metal has shunken afterward. That is why we always end up with low around a proud weld after grinding.

Fact is, some smashing (planishing) of only just the weld itself and after grinding all to one thickness... is required to restore pre-welding crown. Welding from inside can help offset this, but so might the orientation of the door as it cools or the prevailing breeze direction. When stakes are high, I meet the metal snob approach halfway and grind both sides and planish each of the first 1 - 3 rows of tacks. Then I forget planishing and go about half inch at a time from there out.

Repairing bottom edge- Proper length and shape are important but when patching a door shell bottom, its the angle of the bottom flange that counts. And you don't get to find out how you did until final crimp. But that has everything to do with what crown you end up with. Something to keep in mind when finishing out the repair... the edges control the whole thing.

If the bottom folded skin edge is split, you won't get the right contour on your gauge because the old skin is flat. Reference another door or the new panel at the fold. That one will trip a man. Now if you screw the untrimmed patch panel to the old skin, that will pull the old up and thats where it needs to be for marking and trimming. Very imporrant. That assures that while you do the inevitable crown dance, you can know the right amount of metal is there. And when you make that final crimp, ta-da! Suddenly something you thought went sketchy turns out just right with a few more taps near edges.

Copper backing? Just me here and to each his own... I have never had much use for them. Usually goes worse for me if I try it. But where nothing can stick out... go for it.