Quick answer: To weld thin sheet metal without burning through: use thin wire (0.023 to 0.030 in), turn the settings down, make short tacks and stitch welds instead of one long bead, let the metal cool between welds and put a copper backer behind gaps. Gas MIG is much easier on thin metal than flux core or stick.
How we picked: we compared specs, duty cycle and thousands of verified buyer reviews on Amazon.com, with the eye of someone who inspects welds for a living. We have not tested every product in person.
Thin sheet metal (roughly 18 gauge and thinner) is where most beginners give up: the arc blows a hole, you try to fill it, and the hole gets bigger. The good news is that it is a technique problem, and it is fixable.
In my job inspecting welds, I see the same causes again and again: too much heat in one spot, poor fit-up and too much wire. Here is how to fix each one.
At a glance
| Product | Best for | |
|---|---|---|
| Copper Welding Spoon Backer Set (3 plates) | Stops burn-through | Check price |
| YESWELDER 0.030 in Flux Core Wire (2 lb) | Thin wire | Check price |
| IRWIN Vise-Grip 9 in Welding Clamp | Tight fit-up | Check price |
| YESWELDER 4-Piece Welding Magnet Set | Quick setups | Check price |
Tools that make thin metal easier
Copper Welding Spoon Backer Set (3 plates)
Copper plates you hold behind the joint. Weld does not stick to copper, and it pulls heat away so you can bridge small gaps without blowing holes.
- Very effective on gaps
- Flat and curved shapes
- Reusable
- You need a free hand or a clamp to hold it
YESWELDER 0.030 in Flux Core Wire (2 lb)
If you are stuck with flux core, use the thinnest wire your machine supports. Thousands of buyers rate this E71T-GS wire well.
- Popular and well rated
- Cheap
- Gas MIG with 0.023 in solid wire is still better for thin sheet
IRWIN Vise-Grip 9 in Welding Clamp
Good fit-up is half the battle on thin metal. These locking clamps hold panels tight so you do not have gaps to fill.
- Classic, durable tool
- Strong grip
- Buy two or more
YESWELDER 4-Piece Welding Magnet Set
Magnetic squares to hold parts at 45 and 90 degrees while you tack them.
- Cheap
- Fast setup
- Can pull the arc if placed too close
Step by step
- 1. Clean the metal. Grind paint and rust back to bright metal on both sides of the joint.
- 2. Fit it tight. Gaps are what burn through. Clamp the parts so the edges touch.
- 3. Turn it down. Start at the bottom of your machine chart for that thickness and test on scrap.
- 4. Tack every inch or so. Small tacks spread out along the seam stop the panel warping.
- 5. Stitch weld. Weld short sections, then move to a different spot and let the first one cool. Do not run one long bead.
- 6. Use a copper backer. Hold it behind any small gap.
- 7. Keep the gun moving. A slightly faster travel speed and a short stick-out reduce heat.
Which process is best for thin metal?
| Process | Thin metal (18 to 22 gauge) | Notes |
|---|---|---|
| Gas MIG with 0.023 in wire | Best | Smooth arc, low heat, little cleanup |
| Flux core 0.030 in | Possible | Runs hotter; use short stitches |
| Stick | Hard | Small 1/16 in rods and low amps help |
| TIG | Very good | Slowest, needs more skill |
If you do blow a hole
Stop, let it cool, then work around the edge of the hole with short tacks, letting each one cool, until it closes. A copper backer behind the hole makes this much easier. Trying to fill it in one go only makes it bigger.
Keep reading: MIG vs flux core vs stick · Best multi-process welders · Best welding tables
FAQ
Why does my welder keep blowing holes in sheet metal?
Too much heat in one place. Lower the settings, fit the joint tighter, use thinner wire and weld in short stitches.
Can you weld thin sheet metal with flux core?
Yes, with 0.030 in wire, low settings and short stitch welds, but gas MIG is much easier on thin metal.
What wire is best for thin sheet metal?
0.023 to 0.024 in solid wire with gas is ideal. With flux core, use 0.030 in.
How do I stop sheet metal from warping when welding?
Tack every inch or so, weld short stitches spread around the panel and let each area cool before you come back to it.