Tanks A Lot | Sheetmetal Welding Tips and Tricks

01. Here is a tank I was in the process of making for a customer. The pieces have all been cut and shaped to fit together tightly, and the freshly cleaned panels were carefully fit up with zero gap and were TIG tack-welded every inch or so.

01. Here is a tank I was in the process of making for a customer. The pieces have all bee

For many of us, when we start having thoughts of a new ride, we don’t envision throwing our leg over a pile of off-the-shelf parts. Most of the time these parts need some tweaking or need to be built from scratch. You may be simply adding some width to your existing fender to accommodate a wider tire or starting a new tank from a flat sheet of steel. Regardless of the size or complexity of your sheetmetal project, the first place to focus your efforts is making sure you can produce consistent quality welds so you can enjoy the finished product and have confidence in its durability.

When researching welding, many of the available books have good information in general but fail to be very sheetmetal specific. Much of the information is good but directed at heavier fabrication. Some of the reading can also leave you with a lot of knowledge that isn’t easily translated to practical use when you get in the garage. In this article, I am going to try to streamline things I have learned in my years of automotive and motorcycle sheetmetal fabrication. I am not going to spend a lot of time covering the more basic readily available info. Instead I will try to focus on specific things that are likely not included in your welder’s owner’s manual. Hopefully it will be helpful for you in your next project or, if you are hiring work done, give you some insight into the work a quality shop might be doing for you.

02.Here I used a wire wheel to remove surface oxides from the seam inside and out.

02.Here I used a wire wheel to remove surface oxides from the seam inside and out.

First we should look at equipment. In my opinion TIG welding is the only option that should be considered for butt-welding thin sheetmetal. If you are just starting out and expense is a concern, there are some small DC only machines available that are more affordable. These machines do not have the AC capability necessary for welding aluminum and have limited maximum amperage, but for getting started with steel sheetmetal they are fine. A 2 percent thoriated tungsten electrode in either 0.040-inch or 0.063-inch diameters are good choices. The shielding gas is pure argon set to about 20 CFH on the flow meter. The torch’s gas cup should be large enough for good coverage. I find that a #6 or #7 cup works well for most sheetmetal welding. Fingertip controls can be nice in some out-of-position situations but I think more precise amperage control is possible using a foot control. For filler rod, I like to use ER 70S-6 in 0.030-inch diameter. This is sometimes hard to find at welding supply stores in cut rod. It is the same as MIG wire though, so I often times buy it in a spool and cut and straighten lengths to use as filler rod.

03.A hammer and dolly or planishing hammer was used at this stage to ensure the two panels edges were lined up exactly. Notice the tight fit.

03. A hammer and dolly or planishing hammer was used at this stage to ensure the two panel

Probably the most important aspect of welding is keeping the molten metal free of contamination. There are many sources of potential contamination. Oils and other contaminants should be removed first using a clean lint-free rag and acetone or lacquer thinner. Next, even with new steel, there are surface oxides that need to be removed. I use a wire wheel in a die grinder to remove these oxides from both sides of the steel edges. With wire wheels, make sure the speed rating is high enough for use in a die grinder. Wheels that are rated for slower speeds are made for electric drills and come apart quickly at the higher speeds.

After cleaning, the pieces can be tack-welded together. It is very important to fit panels together with as close to a gapless fit as possible. Sometimes people are taught to leave a gap or to use special wing nut panel clamps that hold a gap between panels. I prefer not to hold a gap as I find gapped fits are more likely to take on contamination and allow for increased and uneven shrinkage/warpage. I space tacks approximately 1 inch apart. Next a hammer and dolly can be used to make sure the panels are still flush after tacking. The seam is wire wheeled again on both sides to remove the oxides from the tack welding.