Rounded corners or 90 degree corners when mig welding a patch in?

MP&C said:
If there were a cage that the nut plate dropped into and you needed to drill out spot welds to remove that, you may want the new patch large enough to take care of those drilled holes.. (for example)
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The passenger side does indeed have that cage you're talking about, the drivers side does not.

Here is the size of the patch I was looking to make. My thought was to keep the patch about 1/4" -3/8" away from the existing formed metal since it has better strength?

Door Jamb 2.jpg
 
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Edit, never mind the gauge thickness question, you've already answered that. I'll start calling around and see if any of the metal suppliers out here have 18 gauge.
 
Make sure it's cold rolled so it won't have any mill scale..

So the reason you've heard everyone stress using ZERO gap is as follows:


Door Jamb 2.jpg



Your weld seams are going to shrink, and leaving a gap just allows them to pull together even more as the shrinking occurs for an even greater panel movement. A gap at the outside seam (red arrows) will have the outer panel pulling inward, with likely a low spot just outside that rounded corner. A gap to the inside (yellow) will have the inner vertical flat area and the crease pulling outward. A gap at the bottom will have the inward crease pulling outward, one at the top will have the outward crease pulling in. So as tightly fitting as you can get will help to remove this issue.

If you're worried about full weld penetration, and you should be, turn up the heat! Your welder should be fully capable to do a full penetration weld with a tightly butted panel. Planish the welds to help remove any minimal shrinking that occurred and grind them down flush.

Back to your earlier comment of using rounded corners.. with using sharp 90* corners, the shrinking effects at the insides of the corners will stack up the closer you get in the corner. This will in most cases give you a pucker at each inside corner. A radius helps to better balance those shrinking effects to either side of the weld.
 
MP&C said:
Make sure it's cold rolled so it won't have any mill scale..

So the reason you've heard everyone stress using ZERO gap is as follows:


View attachment 21365


Your weld seams are going to shrink, and leaving a gap just allows them to pull together even more as the shrinking occurs for an even greater panel movement. A gap at the outside seam (red arrows) will have the outer panel pulling inward, with likely a low spot just outside that rounded corner. A gap to the inside (yellow) will have the inner vertical flat area and the crease pulling outward. A gap at the bottom will have the inward crease pulling outward, one at the top will have the outward crease pulling in. So as tightly fitting as you can get will help to remove this issue.

If you're worried about full weld penetration, and you should be, turn up the heat! Your welder should be fully capable to do a full penetration weld with a tightly butted panel. Planish the welds to help remove any minimal shrinking that occurred and grind them down flush.

Back to your earlier comment of using rounded corners.. with using sharp 90* corners, the shrinking effects at the insides of the corners will stack up the closer you get in the corner. This will in most cases give you a pucker at each inside corner. A radius helps to better balance those shrinking effects to either side of the weld.
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Chip Foose is going to be so disappointed with me on how I was going to do it, lol.

Anyway, thank you for your detailed explanation of the proper way to make this patch, or for that matter, any patch.

I'm going to start calling around to find some 18 gauge cold rolled sheet metal. I'll do some practice welds (butted tight) so I can dial in my welder settings to assure I'm getting full penetration before making the repair.

Thank you so much for your input and time. I won't let you or the other SPI members down who told me to butt weld it tight.

I'm very antilitical when it comes to understanding why something is done a certain way. Take no offense for not believing the butt weld should be tight. Now I know why everyone said to butt weld it tight.
 
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For ease of finding steel, Home Depot has it in a pinch. Overpriced but available.
Years ago I tried to “mig the gap” like a buddy did. He’d have at least a 1/16” gap and fill it with weld. But I always ended with too much shrink as described. MP&C described the physics perfectly. Time spent fitting a panel tightly will pay off later especially if you can’t get behind it for planishing.
 
MJM, not sure how far you are from Tulsa, but ARLO metals is a good source for 19 gauge sheet. They even offer 19 gauge draw quality steel which is hard to find.
 
Thanks for metal supplier vendors, Big Dave and Klleetrucking. I went into town Friday to a metal supplier who was nice enough to let me mic what 18 gauge cold rolled he had. All of the material except for the last piece mic'd out from .047 - .050. The last piece I mic'd was .041. So I got lucky.

I'm going to start working on the patch today, and have a little surprise for MP&C.

Yesterday I had to get the door jambs and cowel into primer since the humidity has been high out here the last few days and I was getting tired of re-sanding to remove flash rust.

I have another question about how to weld it up. I now know to make the patch a tight fit, my question is, when I go to weld it, do I make a tac, move forward 3/4"- 1", and continue to move forward until I meet up with the first weld? Then do the same thing until fully welded?

20220710_092536.jpg


20220710_092401.jpg


First round of filler to hide the factory spot welds and press wrinkles.
20220704_203030.jpg


Epoxy applied
20220710_091742.jpg


Epoxy applied drivers door. I masked off the metal to be repaired at the door jamb.
20220710_091717.jpg


Passenger side
20220710_091641.jpg
 
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Good score on the 19 gauge!

On a typical straight seam I would start at one end and tack, working in a uniform spacing to the other end. The idea being to keep the adjacent panels aligned as you work from one end to the other.

On welding a circumferential patch like yours the goal is to keep the patch as exactly centered as possible, so the process changes to accommodate. I would start with magnets holding it in place (this supposes your fit is too tight for butt weld clamps ;)) and tack one side in the middle, keeping the perpendicular sides gapped consistently. (Remove magnets as needed to keep magnetic field away from arc area) This initial tack will have a tendency to pull the patch toward the tack. If you see an opening occurring on the opposite side, planish the first tack until the gaps are consistent. Then tack the middle of the opposite side to lock that down, then the other two sides. At any time if you see the panel has pulled, planish the tight side to get things back centered. After these four tacks are in place you pick a spot and work around the perimeter, adding weld tacks in uniform spacing. Planish each tack to remove shrinking effects, grind welds as flush as you can without touching parent metal, both front AND back side, then overlap each tack 1/3 to 1/2 of the first set. (I aim at the edge of the ground tack). When done with the second set, planish, grind, repeat. I think you’ll find grinding the tacks while they are all lonesome helps to better isolate the next set for planishing by getting the previous one out of the way, and keeps your panel effective thickness as close to original as you can so your heat settings are correct throughout.

Disclaimer: yes, we want an absolutely tight butt joint to limit panel pull, but we’re all human. So when I mention gaps, this means we have gotten it as close as we can and any slight gap that may occur is handled as mentioned above.
 
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MP&C said:
Good score on the 19 gauge!

On a typical straight seam I would start at one end and tack, working in a uniform spacing to the other end. The idea being to keep the adjacent panels aligned as you work from one end to the other.

On welding a circumferential patch like yours the goal is to keep the patch as exactly centered as possible, so the process changes to accommodate. I would start with magnets holding it in place (this supposes your fit is too tight for butt weld clamps ;)) and tack one side in the middle, keeping the perpendicular sides gapped consistently. (Remove magnets as needed to keep magnetic field away from arc area) This initial tack will have a tendency to pull the patch toward the tack. If you see an opening occurring on the opposite side, planish the first tack until the gaps are consistent. Then tack the middle of the opposite side to lock that down, then the other two sides. At any time if you see the panel has pulled, planish the tight side to get things back centered. After these four tacks are in place you pick a spot and work around the perimeter, adding weld tacks in uniform spacing. Planish each tack to remove shrinking effects, grind welds as flush as you can without touching parent metal, both front AND back side, then overlap each tack 1/3 to 1/2 of the first set. (I aim at the edge of the ground tack). When done with the second set, planish, grind, repeat. I think you’ll find grinding the tacks while they are all lonesome helps to better isolate the next set for planishing by getting the previous one out of the way, and keeps your panel effective thickness as close to original as you can so your heat settings are correct throughout.

Disclaimer: yes, we want an absolutely tight butt joint to limit panel pull, but we’re all human. So when I mention gaps, this means we have gotten it as close as we can and any slight gap that may occur is handled as mentioned above.
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Thank you for the welding information, much appreciated. Here's what I did Sunday. Cut the face plate that will be welded to replace the bad metal. I also made a cage for the backer plate/nut. I couldn't let MP&C down since he knows there is suppost to be one, wink wink, lol

Since I couldn't make the cage like the factory did, I came up with my own design. The cage was made with the flanges inverted, rather than facing out like the manufacture did.

My thought was to weld the cage to the new replacement metal, then weld the replacement metal to the door jamb.

Thoughts and suggestion welcome before the welder sets it in stone.

Plates cut and laid out for bends.
20220710_170722.jpg


Cage bent into shape and set on face plate. Backer nut is center line of faceplate hole.
20220710_210616.jpg


Right adjustment from centerline.
20220710_210633.jpg


Left adjustment from centerline.
20220710_210653.jpg


Bottom
20220710_210819.jpg


Top
20220710_210844.jpg
 
Awesome job on the cage, my hint was noticed. I would suggest that the patch is going to shrink from the circumferential weld around it, which will need a bit of planishing despite the nice tight fit. If the cage is going to interfere with that planishing effort, perhaps it would be best to weld the cage on after the fact. I would add that plug welds to hold the cage in place offer very little shrinking when compared to a full weld bead, so here I would rather keep the room inside the b pillar for planishing and grinding and save the plug welds that won’t need planishing for last.
 
MP&C said:
Awesome job on the cage, my hint was noticed. I would suggest that the patch is going to shrink from the circumferential weld around it, which will need a bit of planishing despite the nice tight fit. If the cage is going to interfere with that planishing effort, perhaps it would be best to weld the cage on after the fact. I would add that plug welds to hold the cage in place offer very little shrinking when compared to a full weld bead, so here I would rather keep the room inside the b pillar for planishing and grinding and save the plug welds that won’t need planishing for last.
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Understood, so can I plug weld it from the front of the face plate and grind those weld down? I don't have any room behind the door jamb to weld.
 
Exactly. Get the patch done, then drill the hole where it needs to be, then position the cage to locate the plug weld holes in patch area to correspond to the centerline of the flanges on either side. Three per flange should suffice, but a check of the spot welds on the other side would tell for certain.
 
I screwed up. Sometimes being too focused on something works against you.
I was concentrating to make sure I had a tight fit, which I achieved but, I forgot to radius the corners.

Should I take my die grinder and just tap the corners down slightly on the new patch plate to relieve pressure so the patch plate corners don't curly out ?

Laid out alignment center points and traced perimeter of patch plate
20220711_132500.jpg


Taped up the area to be cut out
20220711_163841.jpg


Area cut out
20220711_170231.jpg


After a little hand filing, the patch is fitted.
20220711_172558.jpg
 
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At this point weld it. You keep cutting and you won’t have any b pillar left :D

Just know you may have slightly more planishing to do at the corner and perhaps a pucker to flatten out.
 
Fitzee addressed the round or square corner issue on one of his videos. He suggested that square/90* corners are fine IF you save them to the last. In other words skip around but not do the corners until the last.

Comments?
 
Fotunateson said:
Fitzee addressed the round or square corner issue on one of his videos. He suggested that square/90* corners are fine IF you save them to the last. In other words skip around but not do the corners until the last.

Comments?
Click to expand...

I would assume that would work, however, I bet those corners will have to be hammered and dolly as the spot welds are made. Those corners are going to grow.

In the repair I did in this thread, MP&C was spot on that at least one of the corners would grow, and it did. I was constantly working one corner with hammer and dolly, all because I forgot to round the corners.

I made another patch on the passanger side door skin. This worked out much better with rounded corners.

20220924_161538.jpg


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20220917_195527.jpg
 
MJM said:
I would assume that would work, however, I bet those corners will have to be hammered and dolly as the spot welds are made. Those corners are going to grow.

In the repair I did in this thread, MP&C was spot on that at least one of the corners would grow, and it did. I was constantly working one corner with hammer and dolly, all because I forgot to round the corners.

I made another patch on the passanger side door skin. This worked out much better with rounded corners.

View attachment 23003

View attachment 23002

View attachment 23004
Click to expand...
Nice work!
 
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