Attn welders. Any tips on patch panel welding?

I don't understand all the hammer/dolly comments....it's like saying the way to travel is by car. End of story. Sure, that is until you hit water.

What I mean is 90% of the sheetmetal welding I encounter doesn't allow you to do any sort of hammer/dolly work. for example, one of the most common repairs is to the lower quarter panels behind the tires. Pretty much every car has an inner fender that prevents you from holding a dolly in the area whatsoever. Floorpans near the trans tunnel? Same story unless your arms are 6 feet long.

So what do you do when hammer/dolly is not an option?

 

GregCon, Good question, I put my GF with a pair of welding gloves under the car on the floor to hold the dolly, she'll clean up at the end of the day!

 

omg !!! your not torch welding sheet metal ... that went out with the invention of the mig welder,,, DONT DO IT

 

You make it an option. Your choice of seam location is really important. As much as possible make your cuts in accessible areas. If thats not possible, quality work often requires removal of other parts, regardless of the welding method. That sounds extreme to some of you I'm sure, but in the in the end the quality you get is worth the effort. Sometimes a helper is needed, but they need to understand the process. This work is not for the lazy, or impatient. It's up to you how far you want to go, or how much compromise your willing to except.

As for any of you that choses to learn and use O/A welding for sheet metal repairs I can tell you you will never regret it, and never go back to a MIG. But it is a skill you have to learn, along with a good understanding of the material your working with. Understanding fuels skill, and skill fuels understanding

 

I didn't read the entire thread, but I'll still put in my .02 cents. For a lower patch panel, I tack one end, and leave a gap across the bottom of the panel. Over a 12" panel, the gap might be 1/8" or more at the opposite end. I start welding at one end, slowly with gas and a very small flame. As I move across the panel, the weld shrinks behind me and slowly pulls the panel up and closes the gap. If I do it just right, the panel fits perfect at the end. A light hammer and dolly work and almost no body filler needed. Of course it takes practice.

 

Before welding, panel fit is most important. I remember seeing a post on here about fitting patch panels "on the go". It looked really cool. Might be worth the search.

 

I'm fortunate to have O/A, MIG, and TIG equipment and have used them all at one time or another. For O/A, there are several small aircraft style torches that work well, even down to jeweler's torches for very thin materials. Another thing is you need to learn to grind correctly, it's amazing how much heat you can put in a panel grinding incorrectly. The abrasive choice is important, too. Unfortunately this stuff seems to come with experience, so learn all you can from those here that have put in the time. Good luck

 

More and more I'm using a file. Before and after hammering. I hate grinding!

 

So what do you do when hammer/dolly is not an option?[/QUOTE]

Tinman is right! Inner structures can be cut out and put back in, they aren't as important as your outer skin. In the end, it all depends on how good you want your work to be. That or 'what the customer wants to pay for'.
When you get the hang of gas welding, you realize how versatile, and easy it is to work.

 

OK...but it's just not that simple a lot of times. For example, my most recent car had an inner trunk extension - the part that hangs down to meet the quarter skin - with many 'corrugated' impressions for strengths. To cut that out just to hammer/dolly the outer skin? You'd never get a weld joint back through all those peaks and valleys that was right.

Accessibility....the single hardest part of doing a good weld on a car.

 

I'm a decent enough tig welder but haven't done too much panel work as yet, despite having ammassed quite o lot of the requisite toys.

I've recently been forced into making a number of floorpan repairs to my daily driver. The patches required involve shaped and ribbed areas and i was struggling to get a good cardboard or paper pattern to transfer to steel. I like to get the fit up as good as is humanly possible so that it welds up well and easily. I do take my time! after my second attempt failed miserably I was royally pissed and looking for an alternative way.

In what I now like to think of as a flash of brilliance i grabbed some 2 inch wide blue masking tape. I covered the hole in tape, overlapping the edges of each piece by about 50%. Then I applied another layer perpendicular to the first. This made the whole tape patch quite stuff but it followed all the contours etc nicely. I then cut the tape out carefully with a (very) sharp blade. The resultant tape patch was then placed onto some clean, virgin metal, sticky side down. I wasn't especting this to stick but the exposed sticky side hadn't been stuck to down anything, so the adhesive was good. This was an unexpected bonus. Carefully cut around the tape, added the shaping and it fitted right in perfectly and was a joy to weld up. I've never heard of anyone doing this tape trick before so unless i hear otherwise i'll claim ownership!

Chris

 

Sorry Dude that's a flexible shape pattern and has been in use for a long time.

I give you credit for figuring it out on your own though!

 

That is the best description of what is occurring when you weld that i have ever read. Very very good.

 

Just found this thread, nice tips here for future use. Later.

 

Also just found this thread, some interesting comments ill take on board

 

heat and metal are never really the best of friends, welding is more about controling the heat so as not to put to much into the metal, keep your fit up as tight as possible and TAKE YOUR TIME, make sure your comfortable, and practice on some junk 1st.