new to body work. butt welding patch panel help

[Schroeder]

Guys, I have problems getting patch panels perfectly aligned and on the same plane. I can always see my weld lines and I don't know where to draw the line on flap dishing the welds down to flush. If I take too much off I get pin holes they the weld and of course weaken it. I can't leave a weld mound on exterior body work though. How do you get yours so perfect? I am thinking of just skimming this, but I want to do it right. Please give me suggestions, tips, and how you would proceed with this patch. I have more of this coming up. I want to patch my ac unit hole on the firewall for a clean, smooth look. I'm sure it will come up beyond that too, so this is a skill I have to get down. Your help is much appreciated.

I'm posting this thru the pro touring app on my iPhone and can't figure out how to add pics to show you. This app works so much better on the droids.

[dhutton]

You need to planish your welds as you go. Here is some good information:

http://www.trifivechevys.com/showthread.php/3042-Planishing-Mig-welds

Flap discs are pretty aggressive and generate a lot of heat. I usually use a small cutoff disc followed by roloc discs to smooth welds.

Don

[dhutton]

More good info:

http://www.garagejournal.com/forum/showthread.php?t=53534

Don

[Schroeder]

I have to read all the articles, but I clicked on the first one. I can never get patch panels gaps to be that close even with templates. That's a big problem too. Idk how everyone else does

[dhutton]

I lay masking tape over the hole and then trace the hole with a box cutter. Then lay the tape on your patch material. Cut it a skooch big and then slowly shave it down until you have a tight fit.

I got the idea here:

https://www.pro-touring.com/threads/56688-Tip-for-making-small-panel-patches


Don

[Schroeder]

Am I going to have to recur the panel out to get the weld lines even or do I just fill in low spots with weld and grind until it all is even ?

[dhutton]

Am I going to have to recur the panel out to get the weld lines even or do I just fill in low spots with weld and grind until it all is even ?

Are you trying to get a perfectly metal finished patch? It's ok to use a little filler, especially for a novice. Adding more and more weld just adds heat and can cause further warping.

Don

[MonzaRacer]

Ok so first things first , head over to ebay and find some of the patch panel holding tools. They leave about a 040" gap, then you tack it into place. See the biggest trick is to let the weld cooling "pull" the patch tight and even, then you have the least risk in warping the area. Putting the patch in tight wont keep it right and can cause issues as you weld it in.use the welds to tie in the metal not a "press fit".
Ask me how I know, the buckle i made was epic and a real big bitch to remove. I had to make 4 cuts and then the amount it over lapped was incredible AND it really did a number on the whole quarter. Luckily I figured out how to realign it and then I rewelded the patch cuts.
After learning the trick I can now weld patches in pretty slick. And they only need minimal skim coats of filler.
The real trick is proper shaping and then fitting it with proper gaps, not tight fit.Those flush panel fitting clips are a great help 282079352644. Thats ebay sale number for those panel holding tools. If its back is hidden you can tack in backing tabs to also lay patch against. Also you need decent flanger to get enough offset if your patch is too heavy a gauge.Yes using TOO heavy of a gauge patch panel can really cause issues also.

[dhutton]

Ok so first things first , head over to ebay and find some of the patch panel holding tools. They leave about a 040" gap, then you tack it into place. See the biggest trick is to let the weld cooling "pull" the patch tight and even, then you have the least risk in warping the area. Putting the patch in tight wont keep it right and can cause issues as you weld it in.use the welds to tie in the metal not a "press fit".
Ask me how I know, the buckle i made was epic and a real big bitch to remove. I had to make 4 cuts and then the amount it over lapped was incredible AND it really did a number on the whole quarter. Luckily I figured out how to realign it and then I rewelded the patch cuts.
After learning the trick I can now weld patches in pretty slick. And they only need minimal skim coats of filler.
The real trick is proper shaping and then fitting it with proper gaps, not tight fit.Those flush panel fitting clips are a great help 282079352644.

I hate those butt weld clamps. I'll stick with tight gaps and planishing my welds as I go.

Don

[Schroeder]

..... If its back is hidden you can tack in backing tabs to also lay patch against. Also you need decent flanger to get enough offset if your patch is too heavy a gauge.Yes using TOO heavy of a gauge patch panel can really cause issues also.

Thanks Mona. I have some of the butt welding clips. I bought them from harbor freight a couple years ago. I didn't use them for this patch panel. I held it flush with the outside with some small, strong magnets. Can you explain the last couple sentences of your post? I don't know what you mean. Also, how can too heavy of a patch be harmful? I used what I believed to be 16ga steel as a patch, but it only measured .035. I believe the edge of the quarter where I had cut measured .029. In the future in going to by lower front and lower quarter patches. I do not have the funds to reprint my car at this time though. The part I patched is behind a whee flares I when I paint it and it looks like crap it will be hidden until I get to do body work On my whole care and reprint.

When people say "planishing welds" do they just mean beating the crap out of it until the 2 pieces are flush and on the same plane?

[jlcustomz]

Planishing is pretty much proper use of hammer & dolly or other flat surface to flatten metal, but proper use of a hammer when talking about sheet metal & bodywork is a lot of precise small hits with hammer, not beating the crap out of it.

While what you're patching on now may not be super important to be perfect, your fabbing & welding now is practice for your next patch, especially if you're a novice.

Different thicknesses of metal can cause several possible issues. one issue is that every material in the world expands & contracts & different thicknesses do so differently. Thicker metal takes more heat to weld than thinner part next to it, can be adjusted for some in welding technique. Then there's flush on each side. Monza was referring to flanging (lap joint) as opposed to butt welding 2 ends together. If you use thicker making a flanged lap joint, then you need to offset the flange deeper to compensate for the thicker metal.

Most musclecar era vehicles will have 20 gauge metal for skin & thicker 18 gauge for some sheetmetal bracing.
https://www.unc.edu/~rowlett/units/scales/sheetmetal.html

A minor amount of filler is expected to be normal after fabbing & welding unless you're doing the highest end work. In areas that will matter, a high spot is worse than a low spot, since you have to fill all around & away from it in an attempt to hide it. Way too much improper filler use. A low spot properly filled may just be your secret unless checked with a magnet, thickness gauge, or hit hard enough to chip.

[MonzaRacer]

Well actually the best way to back up a weld is with copper backer. I have buddy that made several backers with several strong magnets epoxied into milled holes. They work very well.
He even figured out how to put a strong magnet behind patch. Cranked heat up little farther to help with copper sinks.
I have also TIG welded patches.