How to Spot Weld With a Miller MIG Welder

Spot welding with a MIG torch can be done at almost any angle except overhead.

Unlike welding an entire seam between two pieces of metal, spot welding only fuses the metal at single locations pinning the metal together. This is most commonly done with a welding machine specifically designed for this task, a spot-welder. You can, though, spot weld with a metal inert gas (MIG) welder. Miller Electric Manufacturing Company MIG welders are capable of generating sufficient heat to directly spot-weld thinner gauges of metal; you can plug-weld thicker sheets using your Miller MIG welder, too.

Things You'll Need

• Clamps
• Wire brush
• MIG wire
• Welder's mask and gloves
• Plug welding clamp
• Drill
• 7.5 to 10 millimeter drill bit, depending on the thickness of your metal

Instructions

Spot Welding

1. Clamp your metal pieces in place so they do not move while welding. Ensure that you clamp the metal pieces tightly together at the weld location so the pieces have direct contact.

2. Use a wire brush to clean any paint, rust or dirt off of the metal plates you are spot welding.

3. Adjust your Miller welding machine so that it operates at a high amp setting so that you generate sufficient heat to melt both pieces of metal.

4. Strike an arc with your MIG torch at the location for your spot weld. Hold the torch stationary until the heat melts both plates and fuses them together. For a more secure joint, create several other spot welds around the weld location.

Plug Welding

1. Drill several holes through the top plate at the location you want to create a weld joint.

2. Clean and clamp your pieces together. To aid in plug welding, use a special plug welding clamp that tightly grips on both sides of the plug location.

3. Position the torch tip in the center of the plug hole and create an arc against the back plate of the metal being fused. This will cause the back plate to melt and will allow the plug hole to fill with melted electrode wire from the MIG torch.

4. Continue the plug weld until the plug hole is filled and the weld begins to melt through the rear of the back plate.

5. Repeat welding the plug holes until they are all filled and the joint is secure.

Tips & Warnings

• If you are burning through the back plate before the plug hole fills, turn down the voltage to create a cooler weld.

• Always wear protective gear when welding.

• Weld in a well ventilated area.

• Do not weld near flammable materials.

References

• Millerwelds: Spot Welding with MIG
• MIG Welding: Plug Welding