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Old 01-18-2010, 08:00 AM   #1
jteck75
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Default Welding in patch panels

I've got an upcoming project,I have a 1968 Chevy truck that I bought a few years back,my 14 year old son has had a fit for it ever since I got it,and I plan to restore it for his first ride. I have rebuilt the engine,and now I have to take care of some cancer spots here and there. I have a good mig welder,I was just wondering,how do you keep a steel patch as square and flush as possible with the rest of the panel before welding it in? I've painted some vehicles and tractors and did a little bondo work here and there,but this is my first foray into welding in patches. I thought I remembered seeing in an old hot rod mag years ago,there were some kind of clips that you can use,but I'd like to hear from some of you guys exactly what to do. Any help would be greatly appreciated. Thanks!!
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Old 01-18-2010, 08:32 AM   #2
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Default Re: Welding in patch panels

yes, it is. it's best done with tig welder. mig is kind risky, blow through and lots of grinding. you are welding butt joint sheet metal. the key is keep a gap between the panels.

buy a bunch of panel clamps:

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Old 01-18-2010, 08:36 AM   #3
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Default Re: Welding in patch panels

I've used the clamps you speak of, and in some cases find it easier to just use vise grip c-clamps. Depends on the scenario. Here's a couple of different versions I've done:

***************
Time to fix the driver's fender, but this one has more rust action and will need the lower area repaired. It had a galvanized patch spot welded over the rust hole, and we'll get that removed as well.





The repair piece is started by bending the rear flange, and cutting the relief for the lower bend.



The lower bend is made using a 1/4" radius die in the press brake, but can be done with incremental bends in a regular brake.





Some shrinking and stretching of the rear flange on the Lancasters will start to shape the rear edge.



Followed by some "gentle" bends in the press brake again to match that contour across the piece.



Test fit:





We'll save the welding for another night, need to sandblast the inner stiffener to make sure it's solid and epoxy prime all the stuff that will be hidden.

The inner fender brace was sandblasted, with no holes showing up in the pitted areas. A quick check with an ice pick showed it was plenty solid, so the brace was epoxy primed, as well as the inside of the repair panel.







Once the primer has had a few days to cure, we'll start welding and finish the lower fender. The first order of business is to clamp the lower edge flush with the bottom, align the side, and tack weld in place.



It helps to planish out the weld tacks as you go, minimizing any shrinkage issues from the heat



With any welding you are doing, check the back side to insure full penetration, or adjust your machine accordingly. If you need to weld it from both sides due to lack of weld penetration, you just increase your chance of shrinking the area from all the excess heat.



Ground some welds off as I went, gets some of the excess out of the way for planishing the new welds.







The inner fender brace is pulled in snug and plug welded to the lower fender. The rest of the welds are filled in, skipping around as usual to minimize heat buildup, and then ground smooth.







*******************

Time to continue on up front with the fender eyebrows. These parts were primed when we sprayed the inside of the door skins, so they were ready to go. First, both fenders had repairs done already, and the "caps" were slipped over the existing, and held on with tack welds and sheet metal screws. After removal I saw that part of the contour to the inside of the headlight was mashed in so the "cap" would fit better. (thanks for the favor)







The headlight mounting ring will be the next thing removed, but first, let's take some reference measurements on the holes.



Clamped in place and welded on



Next, to trim away some of the leftover eyebrow, so the new eyebrow can be butt welded in place this time around.



It was fitted and trimmed, fitted and trimmed. Repeat as necessary.











The tighter you can get the gaps, the easier it will be to weld.



All tacked in place, we'll finish it up another day.





Well it's about time to play connect the dots, or should I say, let's use some dot weld technology! The existing tack welds from the initial install were planished and then ground down until the were just above the metal surface to get them out of the way. Then I tacked in between these again, and then started to fill in the gaps.





Don't forget to check your welder setup by observing for weld penetration on the back side.



As you weld the heated area of the weld will have a tendency to drop down, almost as if forming a valley. This is caused by the metal shrinking, from the heat. Planish the dot slightly (as needed) using a body hammer with a small dollie pushing up from the inside, and it removes the majority of any deformity.











There are a few slightly low areas, but when the fender is removed next time, the welds will be ground smooth from the back side and some hammer and dolly work should straighten things out nicely.

***********************


AS you can see, the clamps worked well in keeping oddball shapes where they should be, especially when the vice grips just won't reach. One thing to keep in mind, heat from welding causes the metal to shrink, so if you tack weld on either side of one of those clamps, the panel may lock down on the clamp and make it difficult to remove. In this case (when using said clamps) start at one end with your tacks and work toward the other, moving/removing the clamps as you go, so they don't get "trapped" from welding on either side. Hope this helps, good luck!
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Old 01-18-2010, 08:42 AM   #4
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Default Re: Welding in patch panels

WOW! MP&C that's some nice work and great pictures!!


I have done some patch panels with my MiG welder and it works fine IF you're careful and are able to trim all the rust out so you're working with solid steel. I'm all for buying new toys to get a project done, but buying a TiG welder to weld some patch panels on an old truck seems a bit overkill, especially since the OP already has a MiG.
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Old 01-18-2010, 08:48 AM   #5
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Default Re: Welding in patch panels

There's another type called a cleco. They've been around forever. The difference is with a cleco, you overlap the edges.

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Old 01-18-2010, 08:52 AM   #6
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Default Re: Welding in patch panels

As most people have a mig in their home shop, I think you'll quickly find that the tighter your butt joint is, the less chance you have of blowing holes. Next, your heat setting used should be determined by the obtaining of a full penetration weld when welding the dots. If you don't get a full penetration weld, and it just looks like the bead is sitting on top of the metal, your heat is not sufficient. By the time you grind the welds down there will be little holding your patch in and a year or so of road vibration will undo all of your hard work. Now, if you do find you are still blowing holes, before turning down the heat, increase the wire feed. It's like this, if you have enough heat to perform the weld but not enough filler going in, somethings gotta give, hence a blowout. The less the gap, the less the chance of a blowout. Wider gap = more weld filler = more heat = more shrinking = more hammer and dolly work in the end. As far as the TIG welder, they seem to be even more prone to blowing out holes (yes, I have both), and for the novice welder, a very tight gap is almost a neccessity.

Last edited by MP&C; 01-18-2010 at 08:56 AM.
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Old 01-18-2010, 09:03 AM   #7
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Default Re: Welding in patch panels

Nice work Robert. I have also use the sheet metal clamps in above posts and they work well.
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Old 01-18-2010, 09:16 AM   #8
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Default Re: Welding in patch panels

Thanks for the comments guys.

Jteck, you may need this as well for grinding welds:


First off, when grinding, the bigger your contact patch, the more heat buildup you are going to have. so usually smaller = better. Many people for this very reason use the 3" cutoff wheel to grind welds until they are at a manageable level to switch to sanding discs. As a disclaimer, with this cowl section sample, the welds were right next to creases, so I was less concerned with panel movement. If it had been in the middle of a large panel, i.e.: door, fender, qtr, etc, it would be more appropriate to dot weld and planish and grind those dots before welding the ones that overlap the last.









It's kinda hard to take pictures and grind at the same time, but we'll do the best we can.






I use a 3" cutoff wheel, 1/16 thick, and hold it perpendicular to the weld bead. I work this back and forth along the weld bead, covering about a 1/2" area. Don't sit in one spot or it will tend to cut and not grind. next, if we just stayed in the center of the weld bead, you would wind up with a concave depression in the middle of the weld when done, so make a few passes down the middle, then work toward one side, then the other, in attempt to keep what you are grinding fairly flat. Try to stop when you are just above the surface of the sheet metal, or otherwise you will have grinding gouges, like some of the ones shown here:








This takes a bit of patience and finesse (something I'm still working on), but getting rid of the bulk of the weld in this fashion keeps the heat buildup down (less contact area = less heat buildup), allows you to see better what you're doing vice using a sanding disc and thus has less chance of taking away metal on either side of the weld from not seeing what you're doing, and makes the sanding discs last quite a bit longer when you do get to that stage. After the welds are down to a workable level, then I switch to the 3" angle sander, I use a 3" Roloc type 60 or 80 grit sanding disc in the angle sander.





finished the rest up:




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Old 01-18-2010, 09:16 AM   #9
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Default Re: Welding in patch panels

Is your boy doing some of the work? It's a great learning experience for a kid (and a Dad).
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Old 01-18-2010, 11:16 AM   #10
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Default Re: Welding in patch panels

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Originally Posted by djjsr View Post
Is your boy doing some of the work? It's a great learning experience for a kid (and a Dad).
LOL Oh yeah we have a group effort going on with this project. Every time he's over here,we are always working on some kind of project together. He has learned alot from his old man and we are having a blast.
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Old 01-18-2010, 12:22 PM   #11
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Default Re: Welding in patch panels

Autobody 101.com has a bunch of good p00p for home / beginning hammer swingers
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Old 01-18-2010, 12:50 PM   #12
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Default Re: Welding in patch panels

Quote:
Originally Posted by jteck75 View Post
I've got an upcoming project,I have a 1968 Chevy truck that I bought a few years back,my 14 year old son has had a fit for it ever since I got it,and I plan to restore it for his first ride. I have rebuilt the engine,and now I have to take care of some cancer spots here and there. I have a good mig welder,I was just wondering,how do you keep a steel patch as square and flush as possible with the rest of the panel before welding it in? I've painted some vehicles and tractors and did a little bondo work here and there,but this is my first foray into welding in patches. I thought I remembered seeing in an old hot rod mag years ago,there were some kind of clips that you can use,but I'd like to hear from some of you guys exactly what to do. Any help would be greatly appreciated. Thanks!!
You can use panel clamps or if the panels are small a few good strong welding magnets can hold it in place for you to put a few tack wleds down.

Remember to just tack weld it and give it plenty of time to cool down so you don't warp it. Also becareful how hot it gets grinding down welds, I've seen many people warp a panel with a grinder without even thinking about it.
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Is your boy doing some of the work? It's a great learning experience for a kid (and a Dad).
Would agree. My daughter was 11 when she first picked up a saw and helped me chop down my rear bumper and weld it back up. My son was two when he started to help me sand, and it now 4 and anytime I go to work on my truck he loves to come help.
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Old 01-18-2010, 01:29 PM   #13
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Default Re: Welding in patch panels

Obviously MP&C's metal finishing work is stellar and he'll be able to prime, seal, and shoot base right over his repairs without the use of filler. That type of work is tedious and time consuming and is likely to blow away whoever strips the paint off that car next; if they even notice that a repair was done.

However...you don't need expert skill to make these repairs if you don't mind covering your sins with a thin layer of filler. I'm talking about 1/8" max filler thickness, which is a limit that is plenty easy to stay under even for a novice like myself. For most people it's easier to sand the filler to a perfect shape than to form the metal to the perfect shape.

When I watch the guys on Musclecar on SpikeTV do patches, they never planish their welds and the patches are never seamless. They cover the minor flaws with filler.

I am slowly learning to do sheet metal work and believe me, for my own projects I want to become as good as MP&C is. I'm just saying...if your patch isn't perfect and your hammer welding isn't perfect (or doesn't exist at all), you can blend it with filler and it's respectable.
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Old 01-18-2010, 02:49 PM   #14
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Default Re: Welding in patch panels

I just have to say the body work shown is incredible. Very nice bends and patch work.
I have tried a couple of patch pieces on a tailgate and nowhere close to your ability but maybe with lots more practice.
I never knew they made clamps like those, I thought they were just prefabed.
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Old 01-18-2010, 03:19 PM   #15
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Default Re: Welding in patch panels

is that green paint anything "special"?
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Old 01-18-2010, 04:19 PM   #16
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Default Re: Welding in patch panels

Mig Wire size please
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Old 01-18-2010, 06:19 PM   #17
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Default Re: Welding in patch panels

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is that green paint anything "special"?
It's KP-2CF by House fo Kolor, their epoxy primer. I've had fairly good luck with it, so it's what I use. The only downside is that it's NOT compatible with ospho-type rust conversion products. (FYI)

CRus, right now it has .035 in it. I have used .023 on sheet metal as well, but for my machine set up, my technique, etc, the .035 works better for me. The .023 and .035 are both within the range of 18 ga steel, so take your pick. I tell people to adjust their machine heat setting and wire feed per the post above, and if you still can't get it dialed in, then as a last resort try a different wire size. Most machines will have enough adjustment to use either size, but some of the cheaper (HF type) may not have as much adjustment, where a wire size change may make the difference. I've always been told, try the cheap stuff first when attempting to fix something. To me, a machine adjustment or fine tuning one's technique is about as cheap as you can get. Spend money on new wire once you've exhausted those efforts.
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Old 01-18-2010, 10:11 PM   #18
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Default Re: Welding in patch panels

What kind of welder are you using? Amazing work btw!
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Old 01-18-2010, 10:28 PM   #19
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Default Re: Welding in patch panels

Wow, this was all done with MIG? I'm certainly no expert at this, but I was under the impression that MIG wire was too hard for such fine work and would crack during the planishing process, esp if the weld was still warm.
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Old 01-18-2010, 11:04 PM   #20
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Default Re: Welding in patch panels

With sheet metal the gap is not necessary, I try to have little to no gap when doing patches. The clamps work great when you need them but that is pretty rare. The trick is to do tacks, alternate around the panel and give plenty of time to cool, let them air cool and NEVER accelerate the process with water, damp rag, compressed air. Accelerating the cooling process will create brittle and weak welds that can crack later in time. As shown above you should occasionally grind down your tacks to see where you are at. Make sure the metal is clean, no paint, oils, etc., this will keep the weld clean. One thing that I will point out is in the pictures above the metal has epoxy primer on it, this will be debated but this is generally a bad idea. If it is absolutely necessary then make sure it is ground off about 1" away from the weld area, not only will it dirty the weld but it ends up needing to be ground off later anyways. As for wire size, .023 is pretty much standard, .035 can be used on the thicker metal but not all cars have 18ga. sheet metal. Clecos are a bad idea, this is not their intended use and flanged patches are a huge no no, they will retain moisture in the flange and fail in short order due to corrosion.
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