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Metalshop 101 Part 2

Posted in How To on March 1, 2013
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Last month we kicked off our multi-part series aimed at introducing the novice and intermediate garage fabricator to some basic welding equipment and tips on how to use it. We covered MIG welding steel, which is pretty darn easy. This time around we’re covering a topic some novice welders don’t even know is possible: MIG welding aluminum.

When most people think of welding aluminum they automatically think of TIG (tungsten inert gas) welding. While TIG welding aluminum is more common, you can easily MIG weld aluminum material with great success. The only caveat is you should only MIG aluminum that’s 14-gauge or thicker. Any thinner than that and TIG makes more sense because the TIG offers far more finesse and won’t blow holes in the delicate material.

Before you jump on a used spool gun or buy a one new online or from your local welding shop, make sure the spool gun you’re considering will be compatible with your MIG machine. When in doubt, it’s best to stick with the same brand as your welder. For us, our used Miller Spoolmate 200 plugged right in to our Millermatic 212 welder.

As far as equipment goes, it’s not really feasible to just load a spool of aluminum wire into your MIG machine and expect everything to be fine when you pull the trigger. Trying to feed soft 4043 or 5356 aluminum welding wire down a 15-foot gun and have it come out the nozzle smoothly just ain’t gonna happen. Aluminum welding wire isn’t much firmer than undercooked spaghetti, so a spool gun is used to provide the wire a shorter distance from spool to nozzle tip to avoid kinking and jamming.

There are many different types of spool guns offering different ranges of duty cycle, features, and output levels. Since our MIG machine was a Millermatic 212, for us the Miller Spoolmate 200 Series made the most sense. With a street price of just under $700 new, we picked up a used Spoolmate 200 with regulator. The unit features on-the-body wire speed adjustment, toolless barrel removal, a two-stage trigger, an easy-access spool compartment with adjustable drive roll tension, and 20 feet of cable for a good working range. The Spoolmate 200 (160 amps at 60 percent duty cycle) packs more performance than the smaller, less expensive Spoolmate 100 (135 amps at 30 percent duty cycle) and is slightly easier to wield and control on thinner material than its bigger Spoolmatic 30A big brother (200 amps at 100 percent duty cycle). The Spoolmate 200 should be plenty for any at-home welding job that the average guy in his home shop or garage would ever throw at it.

Speaking of gas cylinders, you’ll need a new one. You can’t weld aluminum with the standard 25/75 percent CO2/Argon steel mix gas. You’ll need 100-percent Argon. We bought a 60 cubic foot cylinder at our local welding supply shop for $145. Filling it with Argon was an additional $80, which is just about what it costs to fill our 125 cubic foot steel mix cylinder. Nobody said working in aluminum was cheap!
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