Just ordered rear wheel arch panels for my 74 F250 and would like to try welding these in on my own. Hoping someone could give me a short step by step on what I should do to cut out the rusted wheel arches on the box and weld in new ones.

I have only welded a patch panel once before on this truck with the help of an old friend, so my experience is very limited. Could use a little guidance on the steps I need to take to make sure this turns out ok.

Thanks,
Chris

 

Cut the new patch to the size you wish, & lay or clamp it where it will finally go ,Take a scratch all & scribe arond the new part ...Remove the patch & cut the old panel , 1/2 to3/4 of an inch inside the new panel...What type of welding are you planning......

 

Why do I cut the old panel out about 1/2 to 3/4 inside of the new? Would I then have to trim the new panel down to fit the space? Also, would I cut the space and the new panel so I have a tight fit to each other, or would I leave a 1/8 or 1/4" gap between the new panel and the rest of the box to fill in with weld? I think I've seen that done on one of those Saturday truck shows.

I assumed I would try to get my hands on a wire feed welder. Again, I have no idea what I'm really doing, so any sugestions on how to properly cut the panel to fit, weld it, and what type of welder to use would be greatly appreciated.

Thanks for the guidance

 

If you are going to butt the pieces together you might leave a slight gap (maybe 1/32-1/16 inch maximum) between the repair piece and the original. With a lap joint the new piece will overlap the original by a half an inch or so. One piece or the other will need to be bent with a flange tool to recess it enough so the other piece can fit flush to the surface. The butt joint will not be as likely to show after a few years of heat fluctuation due to the sun, winter etc.

You will need to make sure you have an excellent feel for your welding method BEFORE you start, take some scrap pieces of the same thickness as the repair and original pieces and practice with the everything held a a similar angle that you will be working on the vehicle before you move to the vehicle. Your practice sessions should tell you what gap you actually need. An 1/8 to 1/4 of an inch gap would probably turn into a nightmare.

Make tack welds along the joints several inches apart, dolly the metal, grind the tacks down then make new tacks halfway between the ones you put in on your last pass. If you do not dolly things out prior to the next pass you will lock in any distortion.

 

What do you do if you can't get behind the patch panel to "dolly things out" ? I am getting ready to put new cab-corners on this weekend and there will be no way to get behind the cab-corner after I weld it up.

Many people swear by 3M Panel Adhesive and say it as strong as welding and there is no heat to distort your sheet metal. Not to mention you do not have to buy a welder if you do not already have one.

 

You might need to buy or fabricate a dolly with a long extension handle. Ive used a crowbar before. You can also cut an access hole to get the dolly in or maybe use a stud welder to attach pull pins to the outside. A little distortion on an interior panel from welding it back in wont show like on a finish panel outside.

I did see a thing in a car magazine (Street Rodder) a few years ago where a guy used a compressed air gun (with a copper tube soldered on to put the air right at the weld) to cool the weld area right after each tack was made. He attached the air gun to his mig gun with zip ties, I always worried it might cause more hardening and a possibilty of cracking later but they claimed it worked well.

Another thing is ten hits with a small hammer will move your metal with more control than one big hit with a larger hammer.

Copper backing sheet (ive made many from copper plumbing pipe) can be used behind your panel to help control burn through. Slice the pipe parallel to the length a couple of inches and then make a perpendicular cut at the end of your first cut about halfway through. Use pliers and a hammer to open the pipe and create your flat sheet, leave as much pipe as necessary for a handle.

In any case go slow and let every thing cool down before adding new tacks. You have to control the distortion as it occurs rather than trying to fix it at the end.

A small air angle grinder with abrasive disks wont put as much energy into the panel and thus wont add distortion from the beating of a 4.5 or 6 inch grinding wheel. Mine uses 2 inch 3m 36 grit discs. Its about 4 or 5 inches long. Your grinding will be more efficient if you watch the scratch pattern and once you see scratches going one way (ex vertical) move the grinder so your scratch pattern goes the other way (ex horizontal). That way your abrasive is always grinding the peak off from the last pattern. Dont let the surface get hotter than you can touch while grinding down the tacks.

My thoughts about panel adhesive, is that glue should be used for fiberglass because that cant be welded.

 

I just replaced my floor pans using 3m Panel Adhesive. It feels as solid as you would want. When the stuff dried there was a drip on the bottom that I didn't see and I cut myself like it was a knife. Went to sand it down and it sanded just like sanding metal. I got no distortion from the welder and the repair looks great. The only drawback is that the gun costs about $100 and the glue is about 45/tube. I used two tubes for both sides and I used too much but like I said it is very solid. There was a segment on Trucks! last year that showed how to do a cab corner using the stuff. I think you can watch it online on their site.

 

I like using the adhesives with steel flush head pop-rivets but it is awful expensive. If anyone is planning on doing a fair amount of sheetmetal work (like one rusty F series), the money would be better spent on a mig welder.

 

What were the part #'s for the 3M Adhesive and gun you used? I was looking online at "Auto Body Toolmart" and I found two different 3M Panel Adhesives listed there as well as the applicator gun. The two adhesives wwere listed as "3M Automix Panel Bonding Adhesive" p/n 8115 and 8116 and they were selling for $32.39 each. The Automix Applicator gun #4607 was selling for $53.99. Is this the same stuff you used? I could not tell from the item descriptions listed what the difference was between the 8115 and 8116 panel adhesives, anyone know which would be better.

www.autobodytoolmart.com/p-11230-13700.aspx

www.autobodytoolmart.com/p-11231-13701.aspx

www.autobodytoolmart.com/p-13611-16878.aspx

 

Back to my original welding issue...what is the reason for tracing the new panel out, then cutting the space out 1/2 to 3/4 inside what I traced? If I use the butt together method, wouldn't I cut out the old section of the box to match the exact shape of the patch panel, then trim either slightly to get my 1/32 or 1/16 gap between panels for welding?

I don't have a crimping tool (or for that matter a welder yet), so I think I will butt the two together instead of overlapping. Does this seem the logical steps to do?

Thanks
Chris

 

I just welded a new corner in my cab and a pair of fender patch panels. I agree that the crimping method with its overlap is a good method, but I chose butt joints as they do not have any overlap that can retain moisture. (You might be able to seal this up by also welding the inside.)

My contribution to this thread is to mention the Eastwood (sponsor plug) tool that clamps butt-welded panels together. They come four to a set and hold the metal panels aligned at a nice gap for welding. My only difficulty is that one must space the gap a tiny bit more than the thickness of the tool's blade or it will be difficult to remove without doing minor damage to the tool (ask me how I know).

P.S.: The air blast cooling is a good idea - - I'll use it myself in the future to speed things up. You will not harden the low-carbon steel panels, but do not cool too agressively or you will create more distortion than you want.

 

It depends on your ability .....Butt welding is more dificult..

Rick....

 

You only cut 1/2" inside your trace if you are going to flange and then weld or possibly glue your patch panel. Usually it is best to butt weld patch panels when possible. but it is much more difficult. I like to use a copper backing plate on the back side of the butt weld to prevent burning through the metal. If you decide to butt weld your patch panel make sure you get a MIG welder with the argon/CO2 shielding gas with very small gauge welding wire (~0.026"). Once you have your welder you should plan on practicing welding butt joints a lot before you try to weld your patch panel. You'll also need a hammer and dolly set to straighten out the warped sheet metal as you go and a grinder to grind down the welds. These are some of the reasons I plan on using panel adhesive for the two outer cab-corners I am replacing now. With the panel in place I will not be able to get behind it to hammer and dolly it back out, so I decided against welding them. Even I don't plan to weld in my cab corners I still needed the MIG welder to fix the after market cab-corners I bought that did not fit for *****. I plan to use the MIG welder for the other patches I have yet to do, where I have access to accommodate the process. I know a lot of you are skeptical about panel adhesives and think that welding is the only way to go, but the person who turned me on to panel adhesives is actually certified industrial welder who also works on auto restoration on the side. I was on a website earlier today where they claimed that the 3M Panel adhesive was 11 times stronger than welding. Another guy said he had the chance to inspect a truck that had many panels attached with the 3M Adhesive after a severe roll over accident and all the panels held together, they were not too pretty, but they held.

I have attached a link to some photos showing my cab-corner repair so far:

 

The idea of putting an air hose directly on a MIG gun is really absurd to me,first off..MIG uses gas(argon or CO2),fluxcore is gasless and rarely anyone will use fluxcore for thin sheetmetal as in body panels.
Blowing air directly on the weld will blow away the gas needed for the solid wire MIG uses.
Another thing i see alot of folks say,trying to cool the weld quickly by a wet rag or blowing air on it,a weld will pull more by doing so,causing more distortion in the sheetmetal,the only way to get the least distortion is to tack here and there FAR away from each other and letting it all cool very often on its own.
We use the fast cooling method to remove dents in steel or chemical tanks with dents,heat just the dented area up,throw a wet rag or direct water onto it,causing it to pull/shrink up where the dent or bent peice is.
i would NOT recommend cooling a tack weld in this fashion on light sheetmetal you are tryin to keep from distorting as much as possible,it will only make things worse.
Ive welded several patch panels in vehicles and very little distortion but only by having pateints and only tack welding here and there a few times far from each other and sitting back waiting for it all to cool totaly,and then continue a few more.
Where most people make mistakes in ANY type of welding is they get in a hurry.
Relax,take your time and pay attention to the details and the end results will be rewarding.