Technical BODY, a patch panel from start to finish

I see that some good information on patch panels has been posted. This piece is kinda long, so I thought I’d start another thread. First, understand there are many ways to do this. This is one of the procedures I use for simple panels like this 63 Impala fender. It’s what works well for me.

In the first picture the area to be replaced is marked. There is a brace behind the rust out that is still in good condition. I marked my cut lines in areas where I could get to the back of most of the weld to hammer it. I also like to use curved corners, rather than 90 degree corners in the open areas of the panel. This seems to help keep distortion down.

 

I cut the 2 spot welds along the edge with a spotle tool. Any spot weld drill could be used, or you can grind thru the top layer of metal at the weld to remove the piece.

 

After removing the section, the brace should be cleaned up. I wire brushed this area, and treated it with conversion coating after the metal work was done.

 

I started the patch by braking a 90 degree edge in a piece of 18 ga.

 

I used a shrinker to pull the crown in the patch. If you don’t have one you can cut and weld the flange. The important thing is that you take the time to fit the patch well. It should lay flat without clamping.

 

Once the crown is correct, then the patch is trimmed to fit. I like a slight gap, about 1/6” and even all around the patch. Again, take the time to fit your patch and the job will go easier, and you finished product will come out better.

 

I held the patch with magnets for the first tacks.

 

In this picture the patch is tacked in place, and I’ve started skip welding the seam. I use gas welding for all my sheet metal work. This way the tacks and the welds can be stretched by hammering them over a dolly to compensate for the shrinking caused by the heating and cooling of the metal during welding. It’s a common misconception that warpage is caused by heating. The real damage comes from the shrinkage of the surface area when the metal cools. I use compressed air to cool. Never water. (Unless I’m using a shrinking disc). Even when I’m using air, I cool the weld slowly, and only use the air after the weld has been hammered.

 

More hammer welding.

 

Welded.

 

After some hammer and dolly work, and the first filing, you can see the highs and lows.
Guide coat will help identify high and low spots for more hammer work

 

Here’s the fender after more pick and file work. How far you go depends on the amount of time your willing to spend. This repair will not be a metal finish. Nothing wrong with a little filler.

 

This last shot shows the fender ready for filler. I finish metal in 40 grit for filler work. That’s plenty course enough for adhesion, and fine enough that you don’t loose too much metal in the grinding process.
Thanks for looking, Tin.

 

Nice tech! So do you hammer each weld as soon as you tack it? I'm trying to get my nerve up to try

 

Yep, hammer each tack, and hammer each stitch weld. (I weld 1/2" to 1" each time) Don't make the next weld till the metal is cool enough to touch. Correct the metal with hammer and dolly between each weld. This is not as hard as it looks! I'll never weld sheet metal with a mig again

 

Thanks for the advice. I plan to practice on something less cool before tearing in to the 46

 

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I finish metal in 40 grit for filler work. That’s plenty course enough for adhesion,

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Do you throw filler onto bare metal, or spray some primer first? I always heard to use a primer coat. I shall be coming to this filling and finishing stage on my Morris very soon.

 

Bare metal.

 

Great post.

Hey guys, hop over to the TECHOMATIC, overspray covers the Bondo part pretty well.

Also, kudos on CLEANING YOUR METAL!!!!! It drives me nuts to see guys welding a rusty piece onto a part slathered in old paint!!! You metal sinners know who you are!

 

EXCELENT demenstration!

pay attention boys and girls THIS is the RIGHT way to do sheetmetal work. BEAUTIFUL!!!

 

Man, if it only was a '64 fender you fixed, then I would be SET!

What do you do with the torch when you do the hammer and dolly work? Do you have a "holder"? And what kind of torch head is that you're using?

 

Hey Tin Bender,
Which gas welder unit are you using? I have seen a couple out there, notknowing which one to get.

Mike

 

looks like he is using a HENROB torch. AWESOME setup but they run about $400 for the unit itself. it offers super fine flame adjustability. i used Fab32's once and it was awesome!! it's on my wish list.

 

Okay dont yell to loudly but i have to know the answer..I know i messed up trying to weld to much of the panel at one time so thats where i got alot of bad wrinkles..i also didnt leave any gap so i'm learning here..but do you weld your stitch and hammer it right away? I was going back and getting it red hot and hitting it which i guess is a bad thing also i was using a rag with water.

 

Thanks guys!
Yep, using a Henrob. Very nice torch, worth every penny they cost. But you can still get good results with a standard o/a torch. Try turning your pressures down some and using a small tip. (Make sure your O/A set up has anti-backfire valves)
I have a stand that I put the torch in while I hammer the welds. I leave it lit. I hammer each weld stitch while it's still hot. If you don't stretch an area enough, you can re heat, and hammer again. You can hammer cold too, It just adds some work hardening.
If you stretch too much, you can heat the area again, and cool it to shrink, or use a shrinking disc.

 

Cool post, I guess I need to figure out how to weld with my Henrob instead of just cutting shit with it, now that I have a plasma cutter on semi-permanent loan in the garage.

 

You prefer the O/A over mig. Why? Less grinding and a more uniform penetration of the weld? This step-by-step can not get any better.....unless we were right over your shoulder in person.

 

Henrob (OA in general)makes for a "softer" weld. It is easier to work and grind since it matches the parent metals properties closely

 

Thanks Tin!

Can you explain more about the hammering and dolly part? As you do this you are stretching the metal back out, so do you hammer around the spot the dolly is heeled against?

 

What type welding rod do you use?