For most, our first foray in the world of fabrication, at least as far as welding is concerned, took place at the business end of a MIG (Metal Inert Gas) welder. Arguably the easiest and cheapest method out there, it makes sense that many of us cut our teeth on the process. But as our skillset improves and the demand for a certain level of quality increases, the MIG method starts to lose its luster. Control is minimal, the process is messy, and the end result can leave something to be desired. There are many instances where MIG welding is perfectly acceptable, but very few where it exceeds the results of its advanced cousin, TIG welding.
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This is our TIG welding cart with everything needed to properly lay a bead. Our go-to welder is a water-cooled Miller Dynasty 210. Also on the cart is another Miller item, a Spectrum 625 X-Treme plasma cutter. Both items get used heavily in the shop.
While MIG welding takes some technique to master, the process is literally “point and shoot.” With the gun positioned properly in relation to the workpiece (typically over the joint), a button is pushed and filler wire is automatically fed from the machine into the joint, while simultaneously carrying a preset amount of amperage set to melt or fuse the materials at a predetermined temperature. This results in a joint where the two workpieces are fused together as one thanks to the filler wire. In this case, two methods of control are available from the machine: amperage setting and wire speed. Both settings are typically based on material and thickness (the thinner the material, the lower the setting). Too high an amperage setting will result in melting the base metal before the filler wire (blow-through) while too low will result in the filler wire melting before the base metal, resulting in the filler wire piling on top of the base metal, potentially not even fusing to it. Similarly, too slow a wire feed setting results in the wire melting at a rate faster than it feeds into the base metal, resulting in a non-existent weld, while too fast will feed too much wire into the weld pool before it has a chance to melt and fuse, resulting in a “kick-back” feeling on the gun (instead of the wire melting and fusing with the base metal, it remains solid and literally pushes the gun away). A few other variables, such as technique (like travel speed) and filler wire size, also contribute to a successful MIG weld, but the amount of control on most machines is limited to the amp and wire feed settings, hindering the process.
There’s all kinds of different Tungsten electrodes on the market, but we’ve found the 2 percent Lanthanated version to be great for most all the materials (mild steel, stainless, and aluminum) we typically deal with. Two sizes (1/16 and 3/32 inch) cover the majority of thicknesses we encounter as well and prevent having to stock collets and cups in a variety of sizes. Thicker steel and especially aluminum requires larger-diameter electrodes and related components, and we have those as well.
TIG (Tungsten Inert Gas) welding, also known as GTAW (Gas Tungsten Arc Welding), like AN fasteners and fittings, is another by-product of World War II. Developed as a method for welding magnesium components in the aerospace industry, TIG welding is accomplished by flooding the weld area with an inert gas (typically Argon) and sending an electric arc from a Tungsten electrode in the TIG torch to the workpiece. Filler rod (typically composed of a similar metallurgy as the workpiece) is then introduced to weld the two components together. An initial amperage is again set at the machine, but with the TIG process it can be “throttled” up and down by way of a foot pedal. This makes the TIG process more than just a handful, but a handful and a foot! It helps to be a bit ambidextrous, and a little rhythm doesn’t hurt either, as the dab and move handiwork is better accomplished in tandem.
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When learning to TIG weld, one thing you’ll find is that you’re dipping the Tungsten A LOT. The result is that you’re going to get good at sharpening it as well. For inverter machines, that means creating a sharp, pointed tip, ground parallel to the length of the Tungsten. This can be accomplished on a clean belt sander or on our preferred method, a Tungsten grinding tool. These are specially built with a collet fitted so that the Tungsten is inserted and ground at the perfect angle every time. Its singular function means it’s only used to grind Tungsten so it should be impurity-free, unlike that belt sander, which probably gets used on a lot of different materials. You wouldn’t want to sand an aluminum part on a belt sander before sanding your Tungsten electrode and most of us don’t have the luxury of having space for multiple large machines, especially one for such a specific use, so the small size of a Tungsten grinder is great for this specific task.
This increase of coordination is what makes TIG welding more difficult to learn, yet alone master, which is why most DIYers stick to the MIG process. The introductory cost is also higher, since most TIG machines are more advanced and have an increase of features over the wire-fed alternative. There are a similar number of consumables between the two, with the TIG process requiring slightly fewer. MIG welding consumables consist of the shielding gas, filler wire, and contact tip. The gas and wire are constant consumables while the contact tips are replaced as required, though the process tends to foul these up pretty regularly due to the slag it puts out. Consumables on the TIG welding side consist of shielding gas, filler rod or wire, and tungsten electrodes. Like the MIG process, gas and filler rod are constantly consumed, while the tungsten electrode gets consumed at a lesser rate as the user’s experience increases.
Like the electrodes, filler rod comes in a plethora of sizes and chemistry. Typically, the filler rod size is equal to or lesser than the diameter of the Tungsten to be used, which in turn is dependent on the thickness of the workpiece. On the left is 0.045-inch ER308L rod used for welding 16-gauge stainless steel exhaust tubing. The middle rod is 1/16-inch ER70S-2 that is used for a large majority of our mild steel fabrication. When it comes to welding aluminum, the rod size usually increases, such is the case with this 3/32-inch ER4043 rod.
At the end of the day, both processes can yield a satisfactory result for most home builders, but if a higher degree of workability (hammer and dollying for example), quality (MIG welding produces slag while TIG does not), and consistency is desired, or if a wider range of materials is being used, TIG welding might be the way to go.
The TIG welding process is very fussy and susceptible to impurities, something that isn’t as critical when MIG welding. That said, everything needs to be clean, including the filler rod. PVC tubing and a couple caps make for great, cheap rod storage and keeps the filler material contamination-free. A label on each tube makes it easy to identify the type and diameter contained within.
As a regular user of the TIG process here at Clampdown Competition headquarters, we’ve discovered a few tips and tricks that might help the beginner as well as the experienced TIG welder that we thought we’d share, combined with an overall look at the components required. A few will be givens to those with more seat time, while others will hopefully help the new and old alike. ACP
Speaking of cleanliness, before use we like to wipe down the stainless and mild steel rod with a bit of Acetone, while the aluminum rod gets a thorough cleaning using a Scotch-Brite pad to knock down any oxidation that might be present, the nemesis when it comes to TIG welding aluminum.Between the ground cable, the main torch lead, the pedal wire, and the machine’s power cord, you’ll find that there’s an awful lot of cords running along the ground. Reducing that helps an awful lot and makes moving around the workpiece (like when tacking a chassis together) less of a mess. One thing we can reduce is the pedal’s wire, thanks to a Wireless Foot Control, such as this Miller unit (PN 301580).Viewing the workpiece and weld puddle is critical, so it pays dividends to purchase the best helmet you can afford. We especially like the auto-dimming feature and large viewing area of the Miller Digital Infinity series. The auto-dimming feature allows the user to adjust positioning without constantly raising and lowering the helmet.Being hunched over a workpiece can allow light to enter the helmet, reflect off the viewing area, and make it that much harder to view the weld pool. Since sight is so critical in TIG welding, the addition of a helmet rear extension cover helps block any transient light from ruining the view.When welding stainless steel tubing like what’s found on a stainless exhaust, it’s critical to back purge inside the tubing to prevent “sugaring” and to help the weld achieve full penetration. This Sparc Dual Outlet Flow Meter allows full control of both outlets, the main feed to the machine and the secondary purge line, as they each require separate pressure settings. For instance, we’ll typically run under 20 SCFH for the machine and under 5 for the purge line.A typical TIG torch setup includes a #7 cup and a long back cap. This setup has a number of limitations, as well as benefits. The long length of the back cap prevents getting the torch into tight places, but it allows the use of a common, full-length Tungsten electrode. The #7 cup size also limits the gas coverage available, which is a hinderance when welding materials that like a good puddle coverage such as stainless steel. That small cup size also limits the electrode stickout (typically 3/4 the diameter of the cup), further limiting access to tight joints.On the opposite side of the setup spectrum, we find a #12 FUPA cup and a medium length back cap. Once again, benefits and drawbacks of this setup as well, but this is the one we prefer most of the time. For starters, that huge cup allows for an equally huge area of gas coverage. A diffuser (not visible) provides more evenly dispersed gas coverage without the turbulence commonly found on regular cups (like the one pictured previously). Because the coverage area is so large, electrode stickout can be extended to ridiculous amounts, allowing for easier access to tight joints, especially when combined with a smaller backcap like the one shown. Drawbacks are an increase in inert gas usage due to the larger flowing lens and the need to cut the electrodes to length to fit the shorter cap. For us, the benefits far outweigh the drawbacks.Changing out the cup size and style (diffuser versus non) requires changing out the collet as well to one that mates to the cup. This can get expensive if multiple cups and electrode sizes are used, which is why we tend to stick to two electrode sizes and work from there. That big #12 cup on the right is used primarily for stainless steel only, while the #10 on the left for just about everything else. For these larger cups, the collets are interchangeable. Note the diffusers for each that fit inside the cups and surround the electrode.Like AN fittings, TIG cup sizes are numbered by 1/16 inch. So, a #7 cup’s id is 7/16 inch, which means allowable stickout of the electrode is around 5/16 inch.In comparison, the #12 cup is 3/4-inch in diameter and allows for a much longer stickout.Access to tight joints is one of the benefits to using a larger cup. While we may not need the larger gas shielding area when welding a mild-steel rollcage, the increase in stickout of the electrode makes life a lot easier when compared to the limitations of a smaller cup like the #7.Welding out of position is one of the biggest challenges when TIG welding, as it requires not one but two steady hands. For me, this is any position where I’m not comfortably seated on a stool with my arms resting on a workbench and the workpiece directly in front of me. This situation is rarer than one might imagine, but it’s extremely important when TIG welding to be as comfortable as possible to create a quality weld bead. Oftentimes, it’s not possible. Take a look at the lead image and you’ll see that I’m welding on one knee with the opposite foot controlling the foot pedal. It’s not exactly comfortable, but I’ve positioned myself so that I can easily actuate the foot pedal, view the weld puddle, and have positioned both hands solidly so that the torch and filler rod are easily manipulated. In this image, I had no choice but to stand a length of exhaust tubing on end to access the id of a flange while remaining in a comfortable welding position. A jackstand allows me to rest my right arm so the torch is steady, while the left is free to feed the rod, supported by the flange itself.Welding aluminum is a story unto itself, but one thing should be mentioned regarding preparation and that’s the need to clean ALL oxidation from the surface of the material before welding. One way to do this is to use a stainless steel brush (no mild steel because that will introduce iron to the surface, which results in all kinds of problems, the least of which is rust and contamination) that is ONLY used for this process. The oxidation layer of aluminum is the result of the base material reacting with the presence of oxygen in the atmosphere, similar to how mild steel rusts. This oxidation layer melts at a much higher temperature than the base material, which is why it needs to be removed. If not, the oxidation layer would need to be exposed to such a temperature that, when finally penetrated, the base material would simply blow out or melt away. Removing the oxidation layer allows us to expose the base material to the temperature required to initialize a weld pool and no more, thereby preventing total liquefaction.No matter what material is to be welded, a proper wipe down with Acetone is required. Any rust, oxidation, mill scale, paint, slag, and so on needs to be thoroughly removed before an arc is struck. Failure to do so results in a dirty electrode that will result in a disastrous welding experience and subsequent unacceptable weld.
