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Old 09-04-2021, 04:34 PM   #1
OldCarNewTricks
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Default Welding Patch Panels

The largest repair that I have to do on my 242 is to replace a large portion of the rear passenger quarter panel. I already have an entire panel from a 242 that someone cut from a parts car they had, I am just nervous to get started on it.

I have a Century FC90 MIG, which is a flux core. I've heard from some that if I tack and let cool, I should be fine. I've done a bit of reading online, and seems like maybe flux core is a big no no for sheet metal? I don't really want to get another welder, but I guess I could do so if it is a requirement for this job.

Have any of you guys used flux core for this sort of repair? Any recommendations or shareable experience would be great!

Thanks!
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Old 09-04-2021, 06:41 PM   #2
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This guy is very good.
https://youtu.be/9ZLDNBAwr-s
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Old 09-04-2021, 07:39 PM   #3
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Originally Posted by nel621 View Post
This guy is very good.
https://youtu.be/9ZLDNBAwr-s
Good video. Good to see that when I was trying to do a patch panel last year on a Ford ranger, that the bad result wasn't completely just me. My welder only does down to 18 GA steel, and I've measured my 240's steel as being in-between 21 and 22 gauge steel. Or somewhere around there.

Looks like I will be tracking a gas MIG down for use. This, an Argon tank and some .023" wire should do it.

Thanks!
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Old 09-04-2021, 08:28 PM   #4
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I've ordered an Eastwood MIG 135. Seems to be a decent "middle ground" welder.
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Old 09-05-2021, 05:24 PM   #5
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Good choice on getting a MIG. Flux core just doesn't really work for a good quality repair. What is the area you are replacing? How big of an area? Can you get to the backside?
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Old 09-05-2021, 05:35 PM   #6
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Good choice on getting a MIG. Flux core just doesn't really work for a good quality repair. What is the area you are replacing? How big of an area? Can you get to the backside?
Yes, I'm excited to have something a bit more capable. I intend to keep the flux core for thicker steel, as it does a great job of that.

The portion I'm replacing is the passenger rear quarter panel, from the latch area, all the way to the rear part of the wheel arch. The latch is untouched, it's a couple inches away from it that the dent begins, so I'll likely leave that alone. And then all the damage is below the center trim line.
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Old 09-06-2021, 02:41 AM   #7
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Lowest setting on the welder to get a good weld, and slow as you go. Fit the panels as careful as you can. Weld ,stop look at your work, repeat. When I made my wagon a 2 door the vertical seam on the panel from the top of the wheel well to the window opening took me 45 min. Don't be in a rush.
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Old 09-06-2021, 02:49 PM   #8
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If you are splicing in the quarter panel out in the middle of the panel get yourself a panel flanger tool. You don't want to make a splice like that a butt joint. The pneumatic flangers are anywhere from $40-$150, depending on the make and who is selling the tool.


https://www.harborfreight.com/air-pu...tool-1110.html
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Old 09-06-2021, 08:42 PM   #9
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Originally Posted by 2manyturbos View Post
If you are splicing in the quarter panel out in the middle of the panel get yourself a panel flanger tool. You don't want to make a splice like that a butt joint. The pneumatic flangers are anywhere from $40-$150, depending on the make and who is selling the tool.


https://www.harborfreight.com/air-pu...tool-1110.html
That's a neat tool! I watched a video on how they work and it would be perfect for my repair. I'll have to pick one up for sure, thanks!
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Old 09-06-2021, 08:48 PM   #10
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Practice like crazy on scrap before going to the repair job. You need to get a comfortable position, parts lined up, wire speed, voltage and practice practice and practice some more. If not you discover you finally got it right after mangling your job.
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Old 09-06-2021, 08:53 PM   #11
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Practice like crazy on scrap before going to the repair job. You need to get a comfortable position, parts lined up, wire speed, voltage and practice practice and practice some more. If not you discover you finally got it right after mangling your job.
Solid advice. I think I will cut a portion of the extra quarter I don't need for the repair, cut that in half, and then practice on that. That will give me plenty of room to play with my settings and get everything figured out with the new MIG welder. Thanks!
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Old 09-06-2021, 08:57 PM   #12
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You can also use old hoods and trunks for affordable sheet metal to work with. Also roof panels are good, too.
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Old 09-07-2021, 02:31 AM   #13
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One trick that I do on welding a long seam on a panel, hose clamp a common nail to the tip of the welder at the right distance for the weld. This way you will always be at the right distance as you weld, and go as low heat setting as you can and slow.
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Old 09-07-2021, 10:38 AM   #14
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Quote:
Originally Posted by 2manyturbos View Post
If you are splicing in the quarter panel out in the middle of the panel get yourself a panel flanger tool. You don't want to make a splice like that a butt joint. The pneumatic flangers are anywhere from $40-$150, depending on the make and who is selling the tool.


https://www.harborfreight.com/air-pu...tool-1110.html
I wouldnt flange a patch panel. Theres no way to planish out your weld with the lip behind it. Butt joint would be my go to. Tack it every inch, smooth out your tacks (both sides if you can) then hammer and dolly the fit until its an even transition. Then tack between the tacks, grind em flat, planish it some more, and do that until the tacks are about 1/4" apart and all ground flat. Then stack tacks one on top of eachother until the bead runs from one tack to the next, move 3-4 gaps over, and do the same until they all touch and file them smooth.
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Old 09-07-2021, 11:03 AM   #15
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I would also probably do the butt weld. For the area you describe I think you can get to the entire backside to hold a dolly to planish. It's really important to cut the hole/patch panel dead on with a consistent, small gap. I cut the patch panel to size then trace it onto the car and cut with a thin cutoff tool. There's other methods too, like cutting the patch and the hole at the same time. Panel clamps from harbor freight will let you hold the panel in while you tack. After you got the seam done and ground down, inspect for pinholes with a light behind the seam, weld up the pin holes, grind, repeat. Don't grind too quickly in one spot, the heat can warp the panel. I like a low-grit flap wheel for grinding down the welds.

I don't think you'll need too much practice to do this welding. You just gotta do a bunch of tacks. An auto darkening helmet for this kind of work is key, IMO.
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Old 09-07-2021, 01:16 PM   #16
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There are several reasons not to do a butt weld. OP said he is replacing a large section of the quarter panel. Quarter panels are structural, not just cosmetic like a front fender is on a 240. The seams/joints on a 240 are overlapped for more reasons than just easy assembly with a spot welding robot. The repair procedure you are both describing above is prone to cracking. The idea that you can get behind the quarter panel with a dolly and straighten the sheet metal as you weld it is questionable. Clamping a large section like that will be nearly impossible. I spent 22+ years restoring antique, classic and muscle cars. A small patch on a door or some non-structural area can be done with butt welding and it isn't of concern. I've done that many times. If you are making a large splice such as a quarter panel the flanger is the way to go. Once you have decided which panel is going to receive the flange you can get to work trimming the panels to fit. The punch tool gives you a quick way to prepare the panel that is going to sit in the flanged area. The tool has a built in stop feature which puts the punched hole right in the middle of the flanged area. This works perfectly to solve the clamping problem. Clamp the repair panel along the outer edges where your clamps will reach. Get everything lined up and trimmed perfectly. Then, use the punch to make a series of holes 2-3 inches apart along the splice edge. You have to remove the patch panel to do this set. Then, take an 1/8'" body drill and drill through the punched holes right through the panel behind it. Next, use sheet metal screws to clamp the two pieces of sheet metal together. Depending on how good a fit you get you may only need a screw every 6" - 12". What you end up with is a joint that is stronger than the original panel that is very stiff. IOW, it does not warp when you MIG weld it together. You don't have to do the crappy method of a bunch of little zaps that have little to no penetration and lead to cracking. You may not be able to flange the entire seam due to access for the jaws of the crimp tool. A short transition of a butt weld to the flanged area works fine.
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Old 09-07-2021, 02:37 PM   #17
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There are several reasons not to do a butt weld...
Thanks for the info - good to know.
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Old 09-07-2021, 04:43 PM   #18
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There are several reasons not to do a butt weld...
That makes sense. I haven't really had to deal with that kind of structural repair without going all the way back to the spot welds. Most times I've had to do any larger repairs to rear quarters, its always been easier to just take it to the spot welds on at least 2-3 sides. But things like shaving the fuel tank door or patching in a tail light flange, I've always butt welded.

Cleacos come in really handy when doing lap joint stuff and in my experience, they dont allow the panel shift quite as much as sheetmental screws when you have to remove/replace it a few times to get the fit up perfect.
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Old 09-07-2021, 05:23 PM   #19
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Quote:
Originally Posted by 2manyturbos View Post
There are several reasons not to do a butt weld. OP said he is replacing a large section of the quarter panel. Quarter panels are structural, not just cosmetic like a front fender is on a 240. The seams/joints on a 240 are overlapped for more reasons than just easy assembly with a spot welding robot. The repair procedure you are both describing above is prone to cracking.


The mid panel butt weld on Ely's 143 extended 1/4 panel worked and showed a line / crack in the paint within 6 months.

Best to copy the factory setup and replace the whole panel by drilling out the spot welds if possible.
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Old 09-07-2021, 05:37 PM   #20
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That makes sense. I haven't really had to deal with that kind of structural repair without going all the way back to the spot welds. Most times I've had to do any larger repairs to rear quarters, its always been easier to just take it to the spot welds on at least 2-3 sides. But things like shaving the fuel tank door or patching in a tail light flange, I've always butt welded.

Cleacos come in really handy when doing lap joint stuff and in my experience, they dont allow the panel shift quite as much as sheetmental screws when you have to remove/replace it a few times to get the fit up perfect.
I don't leave the sheet metal screws. I realize I should have spelled out the whole process. Once the panel is welded in place, I remove the screws and fill off those holes as well with the MIG. Usually, I will take a panel completely off all the way back to the original spot welds/seams. When that can't be done, or, it is much quicker to just section the panel I go the route I explained.
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Old 09-07-2021, 05:47 PM   #21
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Quote:
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I don't leave the sheet metal screws. I realize I should have spelled out the whole process. Once the panel is welded in place, I remove the screws and fill off those holes as well with the MIG. Usually, I will take a panel completely off all the way back to the original spot welds/seams. When that can't be done, or, it is much quicker to just section the panel I go the route I explained.
I have to double check, but the guy I bought the quarter from kind of chopped around everything. I'm not sure if all the spot welded areas were cut with it. If they were, I'll split from the factory seams and reweld there.

If not, I'll purchase a flanger tool.

What is the best way to identify spot welds? When replacing the battery tray on my Camaro, it was really difficult to find them. I believe it was rusty, and that didn't help anything, so I ended up kind of chiseling/drilling out. I'd like to be a tad more surgical on something like the quarter panel
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Old 09-07-2021, 05:53 PM   #22
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Use a clean and strip wheel along where the spots welds are and you will clearly see the depression in the steel where the spot weld is located. Get a spot weld cutter. Don't try to split the seams. You will have nothing but a mess on your hands.
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Old 09-07-2021, 07:59 PM   #23
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If you have the entire quarter panel, it makes more sense to go all the way out to the spot weld seams. Even if it's more labor on the panel replacement up front, much easier to weld & less distortion than the idea of doing a vertical weld mid-panel. You'll be doing a **** load of prep/filler work on that to get the proper (un wavy) contour back, I'd bet.

In some ways the small sheet metal (self tapping) screws are easier to deal with than Cleacos, in my experience - also smaller holes to then fill after the fact.
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Old 09-07-2021, 08:43 PM   #24
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I've had a better look at the panel. The only part that I may have to butt weld is the C panel. But I'm not 100% sure. Looks like his blade started to misbehave around that area. Not a huge deal. But all the other seams are all present and in good shape. There is some rust in the lower areas, but not bad. I'll treat the rust and undercoat that portion. It has a very small dent on it, but that will be easy to flatten out before it goes on the car.

I'll have to get some of the spot weld cutters for sure.
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Old 09-08-2021, 12:55 PM   #25
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You should post pics of your issues. Might help with narrowing down which technique would be best.
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