You've just pulled off your helmet and seen a bead that looks like a swollen sausage running down the joint. How to Fix a Fat MIG Weld Bead starts with reading that shape, then making one deliberate change at a time. Most of the time, the problem is an unbalanced arc, not a lack of talent.
Manufacturer setup charts for 0.030-inch ER70S-6 wire on mild steel typically call for 17 to 19 volts and 200 to 260 inches per minute (IPM). As of 2026, consumer and pro MIG machines still use the same basic relationship. When your bead looks fat, you are likely outside that window.
Let's fix it methodically.
Quick Answer: What to Change First
Lower the voltage, speed up your travel, or rebalance wire feed speed. First, identify the bead shape. If it is wide and flat, drop the voltage by one volt.
If it is tall and rounded, raise the voltage or lower the wire speed. Test on scrap steel before touching your workpiece.
What "Fat" Actually Means in a MIG Weld
"Fat" is a welder's shorthand for a bead with too much reinforcement. The crown is too high, the toes are rolled, or the width is out of proportion to the joint. It looks like a sausage, not a smooth seam.
A healthy MIG bead has a slight dome and clean toes. The toes are the two edges where the weld meets the base metal. They should wet out, meaning they blend into the surface without a sharp lip.
On structural groove welds, the American Welding Society's D1.1 code limits reinforcement to 1/8 inch. That's a good benchmark for most non-code work too. Anything fatter is what we're fixing.
But don't confuse "fat" with "strong." A wider weld isn't automatically stronger. In many cases, a fat bead is hiding poor fusion at the toes. The puddle rolled over before it bonded.
That's called cold lap, and it's worse than any cosmetic problem.
The voltage and wire feed speed relationship is central to how MIG works. When those two aren't balanced, you get exactly these fat, misshapen beads.
Read the Bead First: The Three Kinds of "Fat"
Before you touch the voltage dial, look at the weld. Your fix changes depending on the shape.
| Bead shape | What you see | Most likely cause |
|---|---|---|
| Wide and flat | Bead spreads thin, toes don't wet | Too much voltage for the wire feed speed |
| Tall and rounded | Ropy crown, toes barely wet | Wire feed speed too high for the voltage |
| Overlapped toes | Rounded edge rolls over the base metal | Travel speed too slow or gun angle too steep |
Use this table as your decision tree. Then apply the fix in the matching section. The same reading applies whether you're doing bodywork or structural steel, and a solid technique for steel joints keeps these profiles predictable.
Wide and Flat
If the bead is wide and the top is nearly flat, the arc is pushing too much heat into the puddle. The wire burns off before it can build a crown. You'll also see craters or undercut at the edges in severe cases.
Tall and Rounded
If the bead stacks like coins or rolled rope, the wire is arriving faster than the arc can flatten it. This profile often comes with spatter and a popping sound.
Overlapped Toes
If the weld is fat on the bottom but looks like a wall at the toes, you've got cold lap. The puddle rolled over without bonding. This is a fusion defect, not just a shape problem.
Wide and Flat: Lower Heat, Faster Travel, or Both?
A wide, flat bead means you're spreading the puddle too thin. There are three variables that control that: voltage, travel speed, and gun angle. Fix them in this order.
Step 1: Drop the Voltage
Turn the voltage down one volt and keep the wire feed speed at the same setting. Run a test bead on clean scrap steel. If the crown starts to build, you've found it.
Step 2: Speed Up the Travel
If the bead is still flat, move the gun a little faster. Increasing travel speed by 10 to 15 percent shortens the time the arc spends in one spot. The puddle cools faster and doesn't spread as far.
Step 3: Check the Gun Angle
A push angle beyond 15 degrees blows the heat forward and flattens the bead. Keep your travel angle around 5 to 10 degrees, with a slight push or drag depending on the joint. The gun itself is the main tool here, and a good welding gun setup makes the angle easier to control.
Step 4: Watch the Stickout
Keep the contact tip to work distance around 3/8 to 1/2 inch for short-circuit MIG. Longer stickout reduces amperage and makes the puddle sluggish. Too short causes spatter and a wide, unstable puddle.
On thin material, this same fix protects the edges from burn-through. If you're fighting sheet metal, the principles here line up with good sheet metal welding practices.
Tall and Rounded: Fix the Wire Speed vs. Voltage Balance
A tall, ropey bead is the classic sign of too much wire and not enough voltage. The wire feeds faster than the arc can melt and flatten it. The result is a bead that looks like stacked dimes, but hard, rough, and with poor wetting.
Step 1: Raise the Voltage
Increase voltage by one volt while keeping the wire feed speed steady. This gives the arc more energy to wet out the puddle. The crown should drop and the toes should spread.
Step 2: Lower the Wire Feed Speed
If the arc still pops and stubs, cut wire feed speed by 20 to 30 IPM. That reduces the amount of wire hitting the puddle per second. Use the sound as your guide: you want a steady crackle, not a sputtering pop.
Step 3: Hold a Steady Stickout
Your contact tip to work distance needs to stay consistent through the pass. If you push the gun closer, amperage climbs. If you pull it back, the arc gets long and the bead stacks again.
Step 4: Don't Widen the Weld Yet
A weave won't fix a ropey bead. It will just make a wide, ropey bead. Keep the gun straight and let the voltage fix the profile first.
The shielding gas also matters here. With pure CO2, you'll naturally get a slightly stiffer, rounder bead than you would with a C25 mix. That's normal.
If you switch to an argon-based shielding mix, the puddle wets out a bit easier and the bead flattens.
