Patch panel advice needed

I have used the tack and move method for years now. One thing that I have learned to do is keep a wet rag handy for cooling the panel from time to time.
This '65 Buick Convertible is the one I have posted pictures of before with 1 1/2" of bondo on the left quarter panel. They don't make replacements so I had to find a used one and weld it in place. After test fitting I cut out the old panel.
Quarter Interior Rust Treated.JPG

Of course a town of prep work including repairing the rusted wheel well and spraying everything with two coats of epoxy.
Then the tedious process of a gazillion spot welds.
Quarter Install Welding 1.JPG

Finished welds
Quarter Welds 2.JPG

Quarter Welds 3.JPG

Epoxy primer then polyester primer.

LH Quarter - Poly Primer.JPG

I wouldn't know how to do this any other way. I also grind the welds I can reach on the inside as well so it looks factory when done.
One area that I have tried to improve on is cutting the patches to fit tighter as mentioned above by the real professionals. Makes things much easier.
Used Zolatone, a water based material, to finish the trunk area.
Trunk Floor - Zolatone.JPG
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Trying to be the best me, I can be
Don't sell yourself short '68. That's 100% Pro quality work right there. Good Job!:)

Oh and I'm still planning to post pics of the two patches I got left to do on this truck it's just that I'm behind schedule. :mad: Whole job is taking far longer than I planned and he keeps adding on to what he wants to do. So hopefully I'll get to the patches this weekend or early next week.
This was delivered today:
Front Left.JPG

Going to be Destroyer Grey.
Every Time I talk to him, he adds something to the list. Good thing I charge time and materials!
Remove wings, rear deck, tree, front bumper, grill, straighten steps, remove gas tanks to clean and reinstall, etc. etc.
He has ordered parts that will need to be painted but haven't arrived yet.


When you are ready to tack, Run out about a foot of wire on your mig and cut it off. That will purge the line and you can start from there. You should only need to do that when you first start. My 110v Hobart has 4 temp settings and I weld on #3 for 18ga sheet metal. If you look at Roberts picture, you will see how small the HAZ is but also how well the tack is melted in. That is produced by a very hot and quick tack.


John, I'm learning. I have the same welder and have been welding my seams on the second setting with the feed set 35-40. I believe is is also the recommended setting listed on the welder. I can't imagine welding 18ga sheet metal on the #3 setting. Are you increasing your feed? What would be your feed for this?


John Lindsay


.......I have the same welder and have been welding my seams on the second setting with the feed set 35-40. I believe is is also the recommended setting listed on the welder. I can't imagine welding 18ga sheet metal on the #3 setting. Are you increasing your feed? What would be your feed for this?


John Lindsay

John, first, thanks for bringing this thread back up, it contains a wealth of info and should be made into a sticky in the metalworking section.

Now onto the show... Don't be afraid to use some scrap pieces and venture out of your "comfort zone" being what the chart on the machine tells you. I think too many people are of the mindset that you can only control the heat by using the heat control knob on the machine. Consider this once....Keep your heat turned up, control the heat the panel sees with trigger pull duration. Turning down the heat starts to move you toward compromising weld penetration.

For initial set up on a MIG, I look first and foremost for FULL WELD PENETRATION while using a tight fitting butt weld. Anyone can fill a gap, but is it truly fused together properly? If you have weld proud on both front and back side of a tight fitting joint, you have a weld that has taken place. We aren't using a caulking gun here. Next, in the case you do have too much heat as evidenced by a blowout, realize that first and foremost, the one thing you DO have is full weld penetration. The panel is "blowing out" because there is not enough filler wire going in for said amount of heat, hence the panel becomes the consumable wire. So before turning down the heat, add more wire feed speed until you no longer have blowout. Now you are where you can fine tune the settings but more importantly, fine tune the operator of the torch. Get out of your head that the heat control knob controls the heat that the panel sees. If you can increase the heat, increase the feed speed, and decrease the elapsed time of trigger pull, you will in essence have a full penetrating weld with less proud for less planishing needed, less grinding needed. More heat gives you a flatter weld.

The colder your weld, the more proud you have on the top side of the panel, the less penetration you have in the panel. Once you have a cold joint, grind it off. You can pile on another 1/2" of blob, it will never penetrate properly.

And because I have plenty of pictures, here's some test samples that I did. Side note..... you ran out of wire and just installed a new roll. Whether it's the same brand you used before or not, do some test samples if you are welding sheet metal. Always find out how everything works on a practice piece before jumping in on your good panels. Much of todays welding wire is made who knows where of who knows what. Get comfortable with it on scraps.. Also, note the pictures below show my test coupons in free air, just as your quarter panel on a car is. We don't do test coupons laying on a steel workbench because it is a heat sink and does not match the same conditions as the panels on your vehicle. Your practice should match those same conditions as your vehicle, so you are setting up the welder, fine tuning the settings, and fine tuning the operator...…all in the same conditions that exist on the vehicle... before you jump on your good panels

Installed .035 ER70S-7 in the machine, dialed in the settings for 3/16 thick steel, and ran some test welds... YES! HEAT SET FOR 3/16 STEEL!

Note the minimal HAZ for the size of the weld dot, note the minimal build in the side profile shots...………..


Front side....




Rear side....


The duration of trigger pull on these was less than a second, likely about 1/2 second. So the end goal of your practice should be welder setup, adjusting operator technique, and minimal proud/flatter welds having full penetration..
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John Long

I am not going to add anything here John. Robert has summed it up well along with excellent pictures of what you are striving for.

Good job as always Robert.



texasking said:
Makes a lot of sense. Always just tried to make the patch small to limit the area of warpage instead of placing it where I can control the warpage. Thanks for the enlightenment.

Went back through this thread to see if I had missed anything, and I think we can expand on this comment by TK just a bit, may help with understanding warpage. I had done some test welds a few years back and I think the pictures taken will help out here. The tacks were done using the TIG and NO filler for minimal warpage. This also means we need absolutely tight joints... Here's the tacking process, and as said in video, amperage is set at 70. Based on 18 gauge thickness this should have been about 45, but as we also do with MIG "dot" welding, higher amperage and less elapsed time on trigger pull = flatter welds, less HAZ.

Note minimal weld size, minimal HAZ with the higher amperage, shorter burst...


Patches started out flat and for the most part remained so..



Adding a weld pass we are quick to see some distortion...



Examining this further, even though we have absolutely tight gaps for less instance of the panels pulling together, we still see distortion.. This is your typical weld shrinkage as the weld cools. Note in the next picture the panel is still fairly flat along the edges (red line), some shrinking at the weld (yellow arrows) and show a dramatic pucker between the two. Note that the weld has yet to be planished, so the weld shrinkage is pulling the metal alongside it together, the areas unaffected by heat remain largely unchanged (red line) and the area between the two are forming a bulge due to these differing forces. Here we address the problem, not the result. Planish out the weld to stretch it in length and the bulge will disappear. Don't make a habit of chasing the result, a shrinking disc on the bulge is not the correct resolution; if this were a crowned panel that action would be causing a severe low area.


Referring back to an earlier statement I made on weld location:

So if given the choice here, I am using the tallest quarter available and putting the seam: 1) where I have access for planishing 2) in a higher crown area to help control warping 3) near body crease to help control warping (keeping enough distance for dolly placement).

......let's try this same scenario using a crowned sample near a body crease so we can take advantage of all 3 choices...


Weld pass....




Here we can see how the weld location and panel features (crown, body crease) helped to control and limit any warping effects. The weld will still need planishing to restore the crown of the center bead, as no doubt it has pulled in slightly, but this is hands down a dramatic improvement over the flat "patches" we did the first time. This shows how these features in your body panels can help out in controlling weld distortion, so take advantage of these in weld location and leave the limiting of panel size as your absolute last consideration.
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