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When we're attending SEMA we talk to a lot of pro builders and fabricators. We want to know what the new trends, techniques, and products are that they used to get the results we've seen at shows and in the magazines that year. This is one of the ways we can bring you professional tools and products at affordable prices.
This year we noticed a trend with a lot of the builders. Getting the metal work "close" isn't enough anymore. Builders are now striving to make repairs and modifications that are literally seamless and invisible when they're done. Some of the photos I've seen are incredible. These guys are craftsman and the way they form, shape, and finish metal is an art. While I've been using MIG and TIG welders on and off to work on Project Pile House, I've slowly been learning that a TIG welder can be a really great tool for thin gauge sheet metal work.
Project Pile House had a VERY hard life and it was a true work truck before I got ahold of it. It's been used, abused, and modified to get the job done. This included adding lights, mirrors, hooks, brackets, and anything else that "Whitey" (the original owner) felt would help him along the way. This has required a LOT of patch panels to be made up. With the arrival of our new TIG 200 DC Welder, I decided to show you how to make a nearly (I'm no magician yet!) invisible patch panel with it.
The key to strong, visually appealing welds on any project is good "fit-up" of what you're working on. This is especially important when using a TIG welder. Some guys aren't even using filler rod! They're melting the two adjacent metals together only using the parent metals. This means they're making a patch panel that is such an exact fit that it's almost an interference fit (press fit or slightly larger than the opening). This allows the pieces to be melted together with out adding any filler metal. It also requires almost no grinding and yields a perfectly blended patch panel. In this tech article I'll show you the basics of how you can do this, but we'll stick with using filler rod sparingly for now.
This is the area I'm working with above. The truck had some marker lights added on the top of the fenders that were drilled and sandwich into the fender with a second piece of metal under the fender and a nut. Over time the light was bent and broken off, damaging the area around the mounting hole. Rather than work with the pre-existing metal, I decided to cut out the surrounding damage and make a new patch panel. I started by taping off the work area and using the cutting disc on the angle grinder to remove the damaged metal.
You can see above the piece I cut out and the slight curvature to it. I like to keep the original piece around to use as a basic guide for my new patch panel. Next I traced out the shape of the piece I removed (remember we want a tight fit and the part we cut out will be slightly smaller) and transferred it onto some aluminized steel out of our patch panel repair kit. I then used a set of electric metal shears to cut on the outside of the lines I made. This gives me more than enough metal to fit in the opening.
With the rough-cut patch test fitted, I marked out the estimated area that needed to be removed. I then trimmed it down with aviation metal snips and sanded it on the belt sander until I had a very tight-fitting patch panel. From there I put a slight curve in the panel to match the fender and used a metal file to smooth out the opening in the fender. The key here is take off enough metal that the panel will fit snugly without distorting the patch panel or the metal around it.
Now that the patch is in place I set the TIG 200 DC to about 80 amps max. If using the finger switch on the TIG welder, I like to set the machine to a fixed 50-60 amps for sheet metal work. With the pedal I'm able to fluctuate the amperage to get exactly the size weld and penetration I need. I use a 1/16" "red" electrode and either .030 or .035 TIG filler rod. The thin filler rod allows you to make a very small puddle and takes very little heat to flow (melt) the filler rod into the weld puddle. This is nice for thin gauge butt welds like we're showing here. If you need to fill a small void (bad fitment, blown through joint, gaps between welds) I've used silicone bronze filler rod to smooth out a patch panel joint. This filler rod is extremely soft and easy to hammer weld and grind.
After jumping around and fusion welding each side of the patch panel (and happy with the fitment), I began laying very short welds around the panel. Ideally you should only run 1" passes at a time at most (less depending on the patch panel size), letting the panel fully cool between welds. You can also decrease the heat soak across the panel by using thermal paste around the work area.
In between weld passes it's a good practice to "hammer weld" the seam. This is to both flatten the soft weld bead, and also flatten out or correct any heat warpage at the joint. Some like to do this after the panel is fully welded, but I feel it's easier to keep a handle on warpage by hammering the welds as you go. I used the Eastwood pro hammer and dolly kit since it has the hammer and dollies I needed to work the patch panel.
Once the seam was completely welded, you can begin flattening out any "proud" (taller than level) welds with a flap disc on the grinder or with a hand file. If possible try and grind across the weld and only knock the weld down to level. If you are too heavy-handed with the grinder you can easily burn through or warp the metal surrounding the work area and cause a bigger mess than you started with!
Once the seam is pretty level and the panel is free of warpage, you should have a patch panel that is pretty close to invisible. At this point you may even have a panel that is ready for primer and top coat. But for us mere mortals, you can now choose to use body filler or body lead to fill in any small imperfections before primer.
After you pick up the basics of TIG welding thin gauge steel, you can begin welding up patch panels without all of the extra heat, sparks, and mess of a MIG welder. I won't throw my MIG welder away just yet.. but I'm enjoying the lack of holes in my clothes from the sparks and slag it produces!