1970 Front Bed Panel, Warpage Question

[fp1967]

I've got some questions for the metal finishing experts. My front bed panel on my 1970 C10 had some rust holes in it near the top of the panel where the "loop" is. Where the looped over metal is spot welded back to the panel, there was some rust holes at that seam. I was surprised to see this because it is a fairly rust free truck that came from the desert. Some may say to replace it, but where I live in the salt belt, these trucks were all rusted away years ago and parts aren't easy to find.
In the past, I have gas welded body panels and then metal finished them so that no filler other than high build primer was needed. I've only done this a few times and by no means am I an expert at it. When I weld in the second patch on this, I am not going to be able to access the back side of the weld with a dolly (but I'm not that far yet). So I read as many posts on here as I could find on the subject and decided to use a MIG welder and do the dot method. I welded in the first patch which allowed me to use a dolly if need be. I had the piece clamped in place with several swivel pad vise grips. I tacked in place not using a hammer and dolly at all. After it was tacked in, I could see it needed some hammer and dolly work. I then used MP&C's method of welding it in, where you weld one dot then a hammer and dolly to stretch the tacked area out a bit, then grind the tack as he does, then repeat. I didn't take any pictures of the process, only after pictures.

In the first picture, I used a Sharpie to outline where the patch is.
The second picture shows the other side where the second patch will be welded in.
The third picture shows that the repaired area is flat.
The rest of the pictures show the warpage that I have, these areas were flat before I started, so I assume it was my welding that caused this.
I figured that the repaired was shrunk from the heat, so I did some Hammer on dolly work all around the patch to try and stretch it a bit. It didn't fix any of the warpage all around the patch, all it did was create a bulge where my patch was. I used a shrinking disc to get the bulge shrunk back down and now I'm not sure what to do. Sorry for the long post or if I confused you. Any of you experts that can help, it would be greatly appreciated. Ask any questions and maybe I can explain it better.

[hugger6933]

I don't have an answer for you but I can tell you have the stuff to fix it. You are under the same line of thought i am, you can't have too many clamps!!!

[New_70'C10]

I'm not claiming to be an expert on this but years ago I worked with a man that took a torch; heated the metal up (nowhere near red hot) then quenched it with a soaking wet rag. After a couple of cycles of this the metal was practically flat as new. I've seen it on a couple of TV shows since then and it is definitely an art to know how hot to get the metal before cooling it off.

[Steven R]

i have seen a few video of heating and cold water quenching to bring sheet metal back , if this is the method you try take lots of pic pls I have one that will need some kind of treatment later in my project, but I have never tried this myself, but would love to learn... with you on how to repair this keep us posted

anyway subbed

[BigDan3131]

I'm wondering if you plan to build a show truck or if you plan to carry anything in the bed. You have a long winter ahead of you, do the torch method and take your time. Get a scrap panel to get used to doing it so you only have to do it once. Too many cycles of hot and cold will make it brittle. Which side has the issue? The side that faces the cab or the inside?

[fp1967]

Here is some more info on what I have done to it so far. When I started on it, I didn't know the rust issues were there, like most rust, it was from the inside out.

The bottom 3-1/2" of the panel, below the body line, was all dented up. It was, no doubt, used as a truck and had a lot of stuff smash into it. It was bad, looked like somebody took a ball peen hammer to it. I reasoned that if a flat panel was dented, the metal had to be stretched. I used a torch to heat a small spot up on each dent and using a hammer and dolly, I flattened them. It took quite a bit of time, but I got it pretty good.

The next step was the recessed area with the body line surrounding it. It had several small dents and the whole area was cupped shaped (a giant oil can). I used a shrinking disc on a 9" grinder to remove the small dents. I went with the shrinking disc, instead of a torch, because the dents weren't all that big. I then used the shrinking disc to get the whole recessed area flat. I was afraid of over shrinking, so I took it easy, shrinking a little at a time. It turned out quite flat.

Then it was time to strip the rest of the paint off the areas that I didn't think needed any repair. That's when I discovered my rust issues. After I cut it open, to remove the rusted areas, the whole panel remained flat. I was wondering if my previous shrinking had put stress in some places and when I cut it open, it would warp, it didn't.

The issues that I now have seem to be a direct result of the patch that I welded in. My thoughts were that when you heat metal it shrinks, That's why I tried to hammer on dolly the welded areas, to stretch the area that I thought was shrunk too much. All it did was create a bulge, which I shrunk back out with my shrinking disc.

I'm not sure if I need to stretch a particular area or shrink an area, and which area do I do.

[fp1967]

Here are some before and after pics of the dent repair. Another issue that I had to repair was the metal was ripped open in one place near the bottom. It had been crudely pounded back in place then spot welded with MIG, then bondoed. I carefully ground off the weld dots, then got the metal back where it was supposed to be, then gas welded it.

[MP&C]

My responses/inputs written in blue, alternate quote method to remove italics


*quote* I've got some questions for the metal finishing experts. My front bed panel on my 1970 C10 had some rust holes in it near the top of the panel where the "loop" is. Where the looped over metal is spot welded back to the panel, there was some rust holes at that seam. I was surprised to see this because it is a fairly rust free truck that came from the desert. Some may say to replace it, but where I live in the salt belt, these trucks were all rusted away years ago and parts aren't easy to find.

In the past, I have gas welded body panels and then metal finished them so that no filler other than high build primer was needed. I've only done this a few times and by no means am I an expert at it.

I have to say, you would have been ahead of the game to gas weld if you could get a good tight fit, tack in place, and weld in as continuous a pass as you can get. The MIG welding techniques I show are mainly to help out in using a MIG to get results that are similar to what you have seen in gas welding.


When I weld in the second patch on this, I am not going to be able to access the back side of the weld with a dolly (but I'm not that far yet).

First, I would recommend getting rid of the vertical welds. Both of them are going to pull inward and form a valley, and with no access to planish, you will be using filler to overcome the defects. I would say to take the "second patch" from end to end. The bottom flange is spot welded, correct? If you have (access to?) a brake long enough to make that in one piece, it will remove the two vertical welds. The bottom welds will be spot welds or plug welds. The top, if done in a continuous weld pass after tacking in place, should yield the least amount of distortion. See attached for proposed "patch no. 2"




So I read as many posts on here as I could find on the subject and decided to use a MIG welder and do the dot method. I welded in the first patch which allowed me to use a dolly if need be. I had the piece clamped in place with several swivel pad vise grips. I tacked in place not using a hammer and dolly at all. After it was tacked in, I could see it needed some hammer and dolly work. I then used MP&C's method of welding it in, where you weld one dot then a hammer and dolly to stretch the tacked area out a bit, then grind the tack as he does, then repeat. I didn't take any pictures of the process, only after pictures.

In the first picture, I used a Sharpie to outline where the patch is.
The second picture shows the other side where the second patch will be welded in.


The third picture shows that the repaired area is flat.
The rest of the pictures show the warpage that I have, these areas were flat before I started, so I assume it was my welding that caused this.
I figured that the repaired was shrunk from the heat, so I did some Hammer on dolly work all around the patch to try and stretch it a bit. It didn't fix any of the warpage all around the patch, all it did was create a bulge where my patch was. I used a shrinking disc to get the bulge shrunk back down and now I'm not sure what to do. Sorry for the long post or if I confused you. Any of you experts that can help, it would be greatly appreciated. Ask any questions and maybe I can explain it better.









^^^^^Looks nice and flat across the patch, but I would say your straight edge is too short to give a good read. If your patch is about 2' long (for example) I would want a straight edge at least one foot or more to either side to get a good read into the HAZ and beyond, just in case there is some buckling out past the HAZ. Even the aluminum flat bar in your local Hardware store makes a good straight edge and is available in 4' or 6' lengths, just be sure to sight them as you do the 2x4's.





^^^^^This one shows a slight dip along the center of the patch, which may or may not be explained by the linear shrinking of the patch shortening the length of the weld and HAZ along that horizontal seam. This action of shortening one side and not the other would result in the bow you see. But I would say this should be checked with a much longer straight edge (as per above) before taking that explanation to the bank...







^^^^^This shows the bed front bent toward the cab, which one would expect after the past 45 years of stuff sliding around.





Where this one shows the bend in the opposite direction, again the straight edge sample is a bit short. I'd almost say this would be an up and down wave if the straight edge were longer. (subject to correction) Again, a possible condition of stretching from impact damage. The other possibility is that the shrinking from the patch above has pulled at the panel causing this distortion, but this is less than likely given the stepped detail between the two, and why I think you may have some stretching in this area from cargo damage. I would say to check those areas with a longer straight edge, and post up your findings......


*unquote*

[BigDan3131]

I like to use my trucks as they were intended to be used as a transportation device. I still shot mine with pearls and candy on the outside so my bed can take a beating but not like the golf ball syndrome so I shoot them either in multiple coats of rubberized undercoating or if its a more serious use spray on bedliner. What I'm getting at is, its a truck and sweating over the bed more than you have already done will drive you nuts when you start doing cab and fenders trying to perfect the curve. Bedliner can be sprayed smooth and painted too.

[fp1967]

Thanks to those that responded. MP&C, you had some questions and requested some more pics with a longer straightedge. I tried but just can't seem to get any good pictures, so I used a Sharpie to draw out a map of the warpage on the panel, and took a pic. I will try to explain what I got going on along with the pic that I got. The rectangle is where the patch is, the welds are right under the lines. Along the top weld, it is flat and is flat all the way across the panel, there are some slight waves, but this is where all the factory spot welds are and I believe those waves have been in there from new. It is basically a straight panel from one side to the other when sighted like a 2x4. Above this area there is a low spot almost like a valley. From each side of this low spot all the way to either side, it is flat. When you sight down the panel, it has a noticeable bow to it. On a piece of paper, I drew out an exaggerated view looking straight down at the panel and took a pic, pic #2 below. I'm wondering if this low spot needs to be shrunk, being that the panel is straight just below it.

In your response, you questioned the warpage below the patch and thought maybe it was from years of cargo shifting. This whole area was flat before I started welding the patch in, if you could go back to post #6, it would save me a bunch of typing. The areas on both sides of the high spot are quite flat all the way out to the sides, except the low area in the circle which is like an oil can.

I hope that you can understand my explanations and thanks again for trying to help out.

[MP&C]

Anytime you have shrinking in the vicinity of a flange, the outer edge of the flange (that which is farthest away from the heat) will tend to resist any movement where once shrinking has occurred, the low spot should be on the opposite side of the panel as the flange. Looking at your picture this effect seems to hold true:





Where the top edge of the bed front forms a flange, shrinking from welding in the patch has formed a low on the opposite side of the flange. Looking at the step in the panel below the patch in the picture, this is also a flange to the flat area being welded, and the low spot is on the opposite side of the flange. Anytime you have a welded seam, the Weld and it's HAZ will shrink, the flat area far outside will resist any change (be that a flat area or the flange / step seen here) and whatever is caught in the middle will form a buckle as it is caught between the two differing forces. In the case of the step, the shrinking effects were enough that the distortion travelled across the "flange", but the side the flange is located definitely shows in the results of the side the puckers are on. As far as the "low" shown in the middle, in many cases the inherent forces of the panel that are there naturally from the forming process will be pushed/pulled in other directions due to outside forces being introduced. The forming of the pucker across the step appears to be pulling from that area, forming the low, especially if you say it was flat to begin with.

To fix that large "low" area, you fix the forces that caused the pull. In other words, leave it alone and stretch out the area of the welds and HAZ along the puckers. Now, you also have puckers going in two different directions. When hammering/planishing your weld, even though the hammering into a dolly will result in a stretch across the area struck, the hammer will also tend to "persuade" the direction of the panel's travel, in much the same way that the flanges told you which side the low would be found. So when planishing, use the hammer on the low side of the panel, and during any on-dolly stretching it will also tend to persuade the panel back to it's original location.

[fp1967]

Robert, thanks for the reply. I understand what you are saying, but I have one more question. Do you have any idea which area I should start with the planishing/stretching ? When I first got done welding it in, I planished all around the patch and all I did was make a bulge, the warpage that I have was still there. I shrunk my bulge back out with a shrinking disc and that is where I'm at now. Thanks

[MP&C]

The puckers tell you where the shrinking is concentrated, the hammer strikes on-dolly should be from the low side of the panel, if accessible. Planish the weld, and to a lesser extent, the HAZ. If it turned blue around the weld, it shrank as well.

[fp1967]

Thanks, I'll give it a try in the area of the puckers.

[MP&C]

when you created a bulge from your planishing efforts, which direction did the bulge go? Dolly side?

[fp1967]

Yes, dolly side.

[MP&C]

Don't read "planish the welds" as keep on planishing until it raises up where you want it. It doesn't work that way. If the panel has started as a low due to shrinking effects, strictly planishing will stretch, but absent any change in direction, the panel is just being forced the same direction. At some point you need to read the panel, using whatever profile gauges you choose, to see if any bumping is needed to correct the direction the panel is taking.

[tcoop68]

I just seen this I'm sure you know there is a lot of suppliers that sell that complete front section at a reasonable price , but if your like me I like original parts just saying looks like you got it whipped anyway .