Technical Sheet metal panel levelling advice

Gents

Hoping I could get some advice on how the more experienced metal man may approach this issue:

The truck bed I am restoring is not level when you put a straight edge along the top rail - it's high in the middle. The sheet metal is 1mm with a second skin beneath - I did mig weld up some canopy tabs which I cannot planish from underneath which isn't helping the highs but I don't believe that is the sole cause of the issue - it's just been beat up with age. It's higher towards the inner edge of the bed to.

I thought I could bring down the highs slowly with a hammer / slapping file and work it till it was level enough but I seem to be getting to a few main high areas that I cannot get down and seem like Im just pushing the highs around. So I have a 1-2mm gap across a lot of the panel with some key highs that stop it from levelling out. I dont want to beat the **** out of it and make the problem worse - I already put a small few dents in it where I hit where I shouldn't (part of learning I guess)

Any guidance would be appreciated.

 

I bet you can only notice it when you have a straight edge on it, so don't put a straight edge near it! Only you will know. Were they ever that straight anyway?

Chris

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Body panels that are perfectly flat read "hollow" or concave to the human eye, that's why automotive stylists add a little bit of curve to everything. If you want to find out if your pickup bed is OK, find another one, same make, model and year and put the straight edge to it.

 

That's why there is a strip of foam along the bottom of the camper shell edges....

 

Yeah they were never perfectly flat from the factory....I've owned several. Don't worry about it.

 

Use a big f'ing hammer and a block of wood to lower the highs! Works every time....

 

1MM, hell, thats a dime. leave it. Or if it bothers you that much bondo and block it.

 

Understand, I don't condone this...but an old timer flat rate production shop bodyman buddy of mine had 2 sayings, first was "you can't fill a high", and second was "cave and pave".

But I agree with others, don't worry about it.

 

Well I am going with wavy is ok for a work beater/parts hauler but will stick out like a sore *** thumb if you put good paint on it.

That said, mine are going to need a lot of work before they are ready for paint and the top of the rails on my 72 GMC long bed have about a dozen holes in each rail where my uncle drilled new holes everytime he mounted something different on the truck be it canopy, horse racks or ??

 

To remove a high in an area like that, try applying some heat at the inside top edge. The edge will shrink and push down the high.
Conversely, applying heat to the bottom inside edge will raise it.
I’ve use this method several times to adjust rocker to door gaps. You’d be surprised how far it will move.
Or message the high with a hammer and block of wood.

 

like Anthony said heat or BFH and a block of wood

 

Shrinking disc would work.

 

Try coming at it with a super thin cut off wheel, cut a slice in the inside rail to relieve the stress. I had to do this on a 72 gmc bed rail, cut reliefs 1/3 of the way in from both sides and pushed it down till it was a hair low when I welded up the cuts when cooled it was level, and the cuts will open up.

 

As Anthony said..........heat........ BUT you better know what your doing or it may come out worse than when you started. Do as he suggested, keep it in a very small area at the high spot and use water soaked rags each side of the heated area and start out with very little heat. Let cool, (use the water soaked rags for this), check and re do if not what you want with slightly more heat. Heat sticks are available at any good welding supply. I've straightened all types of steel shapes and plate steel up to unimaginable thickness (6 inch) Just do not get in a rush, and once shrunken it will still shrink again. Sheet metal in all gauge ranges can warp badly if done wrong and in some cases will need replacing . Best of luck.

 

Appreciate the advice guys (and your patience with these beginner questions)

I'm doing a full restoration on the truck so hopefully I can get it level. I could body fill it but I want to avoid anything over 1mm if possible.

I will try my shrinking disc on the inside edge although may not be hot enough but at least a novice cannot do too much damage to a panel with one.

When you say block of wood and hammer, what type of hammer are you referring to? I'm a little nervous about really bashing it.

 

Just to confirm my understanding...the inside top edge is the section I have marked red yeah (the bottom inside edge terminology confused me)? If I heat shrink that area it will hopefully pull the section down

 

Yes. The top upper edge. I have used a stud gun and a very small torch tip on edges to move them. Locate the highest spot and apply heat. Quick cool and check. It doesn’t hurt to “m***age” with a block of wood and hammer while warm. Then cool.
I was doubtful the first time I did this. I’ve moved rockers on prewar cars over 1/8 of an inch doing this to open up gaps

 

Appreciate the guidance guys

Didn't have much luck using a shrinking disc to pull the edges down.

With regards to the block of wood and hammer (I don't want to make the situation worse):

a) would the shrinking disc provide enough head to help m***age the metal down?
b) do I need a block of wood to just cover the area I'm hitting or do I need one that runs most of the length of the truck bed?
c) what type of hammer and I'm using? like how hard am I hitting?

I laid down my straight edge and put my bodyweight on sections and while it moved a little it just sprung back up...could I heat up the metal with my shrinking disc and apply body weight force? Is that a technique?

 

You are going to have a hell of a time trying to get that to go down by heating the top with a flange that is as deep as you have. The bottom edge of the flange is too short that's why it is bent up. Take a piece of cardboard with the same dimension as you have on your bed side a fold the 90 degree in it. Now try pushing down on the top and see how much movement you get without the vertical distorting like crazy. It's not going to happen. Now cut vertical slits in the vertical and see what happens. To move the top down the bottom had so get longer (your cuts will start to open up on your cardboard). Hammering on the top is just going to distort the vertical flange (it will either push in or out) as it moves to try and compensate for being too short on the bottom edge.

 

Thanks mate.....if I run my straight edge along the bottom of the flange (outside edge) apart from a couple of small highs that Im sure would shrink down, it is pretty much level...it only gets worse as it gets to that inside edge. Does that run in line with what your expecting based on what yo have said about it being too short? Excuse my ignorance here.

 

The panel has been stretched, need to give the metal somewhere to go.
Im saying the same thing K13 is.
The vertical flange is preventing you from moving the horizontal bed side top. Cut a few slits in the vertical flange, move it up or down until its flat ( hammer and a block of wood), if you have correct shaped dollys you can work the dents out too. Also straighten the vertical flange. Tack the slits and check bedside top for flatness, tack the flange more and check the top for flatness.

I dont know how to tell you how hard to hit with a hammer framing nail hard, trim nail hard, half a swing, quarter swing.....I dont know. Hit it soft and increase until it moves. I use a ball peen with a block of wood, the wood absorbs and spreads much of the force. Any direct metal contact is with a body hammer.

 

Thanks mate, I wasn't sure whether we were still referring to normal hammers with regards to block of wood or moving into big sledge type hammer territory.

 

Sorry guys, I misunderstood the flange bit last night (ignore my earlier post)...you are referring to cutting slits in the bit marked red below.

I appreciate your time guys, I started this project to learn all these skills and it sure doesn't come overnight (especially with no friends who are into this stuff - I realised its hard for you guys to convey this stuff over a computer)....you are saying cut vertical slits (not horizontal) into the flange...but not the whole way down the flange (or am I cutting from where the flange starts on the bend)? I'm trying to theoretically picture what it is doing - I'll have to grab that bit of cardboard.

 

As an alternative, could I totally cut out the flange, hammer and dolly the top flat and then weld in a replacement flange

 

As far as cutting slits. That means welding. That causes shrinking. Could that move it upward even more?
Did the welding cause it to move upward? If so, cutting slits and welding is doing the same thing.

No, a disc will probably not heat that up enough on the edge.
need a better close up of the area causing the distortion.

as far as hammering. If done correctly, it shouldn’t mess up anything. I’ve used that method hundreds of times. You hold the wood block with pressure on the edge. Then hit with the hammer. How hard? Hard enough to move it and light enough not to hurt it. The metal tells ya what,where and how hard to hit. I guess it just comes with doing it a bunch.
This is how ya learn. It’s just cold rolled steel. You can do just about anything with it.

 

You need to check for straightness on everything not just the top. Is the bottom of the vertical part you marked red straight? Is the inside edge, 90 degrees from where your straight edge is now, straight? That will tell you what needs to move. If the bottom edge is straight then one of two things has happened either the side has pushed in which pushed the metal up or it was made with the bend from the factory and the sidewall of the flange is different heights along its length. Anthony's hammer technique will work if its pushed in but you are not pushing that entire flange down with heat and a hammer unless you get the whole thing red hot and wail on it.

The metal has to go somewhere. It has to move down or towards the inside of the bed so it depends on what isn't straight as the where you want to move it. If the inside is straight (90 degrees to you straight edge) hammering on the top is going to push that out and make that line not straight. You need to find out where you need to move the metal before you start hammering or cutting anything.

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without any better pics of the area to diagnose, here are a couple of crude sketches to explain possible solutions.
Each method has a possible side effect.
The small distance you say it needs to move, these side effects or distortions should be minimum.
Heat on the top edge moves the top edge downward.
These are very small heated areas. The orange area of the heated edge should be no larger than 1/8 of an inch. Will it move the bed edge in or out? Possible. But you are not moving it much. The inward or outward movement can be addressed.
The slit method (in my worthless opinion) is probably the absolute last resort. I see that as creating more issues. That process can also move the edge in or out.
Another possible method is stretching the bottom edge. The bottom flange edge can be stretched by hammer and dolly work.
Without a better pic and knowing exactly where the weld is it’s hard to diagnose.

Shaping/repairing metal is an exercise in shrinking , stretching and combinations of both.
Any distortion caused by a weld can be reversed by planishing that weld.
If you can’t access the area to do that, then you figure out a method to counter it.

 

I would try what Anthony is telling you with heat. it doesn't take much. go a little bit and see what you get.

 

Appreciate the time it took for those replies gentlemen....

 

You think it looks bad now. Keep missing with it and see what happens.