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For increasing your production times, MIG welding is often the way to go. But depending on the thickness of the metal, or the type of joint, it may not be possible. Here we’ll give you a quick rundown of when you can and cannot use MIG to weld sheet metal. 

The Density of Sheet Metal

Typically, anything under 16 gauge (one-sixteenth of an inch thick) becomes very prone to blow-through with MIG welding, regardless of the joint you use. If you are experienced and work fast enough, you should weld certain joints with 18 gauge. The trick to pulling this off is what we call a “rush forward, sit back” technique. It’s exactly as it sounds. After starting the puddle:

• Quickly move the torch forward about a quarter inch
• Pull back about half the distance
• Hold momentarily (roughly a second) to fill the puddle
• Repeat

The thinner the metal, the further you will need to move forward before pulling back. This technique reduces penetration because it temporarily takes the heat off the puddle and cools slightly. When you return to add more metal, you do so onto material that has already begun to solidify. 

Which Joints Work Best for Thin Metal?

First off, edge welds and corner joints will be tough to weld with 16 gauge and not possible for anything thinner. Though it is possible to weld these joints on 16 gauge, weld appearance will be poor. It would be much more favourable to use TIG instead, and you will likely save yourself time from having to repair holes from blow-through. The best joints for anything thin. However, are lap joints and “T” joints. With these two, the materials are positioned to absorb more heat and allow you to take the time to produce a more aesthetic weld. 

You will also weld butt joints on sheet metal, but you will need to keep two things in mind. Firstly, your travel speed must be very fast. Second, the gap between materials must be nearly non-existent. As soon as the puddle reaches a gap, you will be forced to pause to fill it, and the subsequent heat that builds up in the workpiece will end in an inevitable blow-through. 

MIG Machine Settings 

Aside from the welder technique, manipulating your voltage and wire speed is another way to control welding sheet metal. We have found over the years that a higher voltage than amperage tends to work better than just lowering the settings for both when working with sheet metal. For example, placing the wire speed (amperage) at 125 with the voltage at 16.8 will allow you to put quite an aesthetic bead on 16 gauge. A lower voltage setting will work as well, though the welding technique will be a little harder to master with no apparent benefits. 

Final Words on MIG Welding

Many times, MIG welding sheet metal can be a great way to speed up production. However, if the joint does not need a continuous weld all-around, or if the metal is too thin for MIG, then consider spot-welding. This whole welding process requires different equipment but may be essential to reaching even higher production times.