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Pulse TIG can make thin sheet easier to control, but it does not prevent burn-through by itself. The useful settings depend on the metal, thickness, joint, tungsten, and how quickly you move. Treat the numbers below as starting points, then make a short test weld on the same material before working on the part.
What pulse does on thin metal
In pulse mode, the machine alternates between a higher peak current and a lower background current. Peak current briefly melts the joint; background current reduces heat input while helping keep the arc established. This can make it easier to manage a small puddle and limit distortion, especially on thin stainless steel.
Pulse is not a substitute for correct fit-up or travel speed. A gap, dirty surface, or pause at the edge can still cause a hole. On very thin material, steady DC TIG without pulse may be simpler if you can move consistently and use a foot pedal or hand control.
Starting settings for thin sheet
For DC TIG on mild steel or stainless, try these initial settings on clean material. They are not universal: joint design, torch angle, backing, and machine calibration all affect the result.
| Material and thickness | Peak current | Background current | Pulse frequency | Starting duty cycle |
|---|---|---|---|---|
| Steel or stainless, 0.8 mm (0.030 in) | 25–40 A | 25–40% of peak | 1–2 pulses per second | 30–40% |
| Steel or stainless, 1.0 mm (0.040 in) | 35–50 A | 30–45% of peak | 1–2 pulses per second | 35–45% |
| Steel or stainless, 1.5 mm (0.060 in) | 45–65 A | 35–50% of peak | 1–2 pulses per second | 35–50% |
Here, duty cycle means the portion of each pulse spent at peak current. A 40% setting spends less time at peak than a 60% setting. If the machine labels pulse width or peak time instead, check its manual before translating these values. For aluminum, these DC settings do not apply: TIG aluminum normally requires AC, and the machine’s AC balance and pulse controls add variables.
Set up the joint and torch
Remove oil, paint, rust, and mill scale near the weld. Stainless steel should be cleaned with tools reserved for stainless to avoid embedding carbon-steel contamination. Fit the pieces tightly; a gap wider than the sheet thickness can make a thin butt joint much harder to bridge. Tack at short intervals, alternating sides where practical, so the parts cannot pull apart as they heat.
A sharpened 1.0 mm or 1.6 mm 2% lanthanated tungsten is a useful choice for low-current DC work. Use a small cup—often a No. 6 or No. 7—and enough argon flow for coverage without creating turbulence. Around 10–15 cubic feet per hour is a common starting range for a modest cup in still air. Excessive flow can disturb shielding; drafts can spoil it even at a sensible setting. A basic TIG argon flowmeter helps confirm actual flow at the torch.
Tune pulse one control at a time
Begin near the low end of the peak-current range and use a comfortable background current. Set pulse frequency around 1–2 pulses per second if you want time to coordinate filler addition with the pulse. At higher frequencies, such as 50–100 pulses per second, the arc may sound and feel smoother, but the pulses are less useful as a visible rhythm. High frequency does not automatically mean less heat; average heat still depends on peak current, background current, duty cycle, and travel speed.
Run a short bead, then change only one setting. If the puddle is slow to form or the bead sits on top, raise peak current slightly or increase duty cycle. If the sheet sags, the edge washes away, or the heat-affected area grows too wide, lower peak current or duty cycle, increase travel speed, or reduce the time spent on each section. If the arc keeps going out during the low part of the cycle, raise background current. Do not compensate for poor fit-up by turning every control up.
Keep the arc short—about 1–2 mm—and hold the torch at a modest angle. A long arc spreads heat and weakens shielding. Use small filler additions rather than pushing a long wire into the puddle. For a lap joint, aim the arc toward the thicker lower piece and let the puddle wet the thin edge; pointing directly at the edge is a common route to burn-through.
Pulse versus a foot pedal
| Control method | Best fit | Trade-off |
|---|---|---|
| Panel-set pulse | Repeatable short beads and work where both hands need consistent movement | Settings stay fixed unless the machine has a torch control; technique must match the preset |
| Foot pedal or fingertip amperage control | Changing joints, corners, and parts that heat up as welding continues | Requires coordination and a compatible machine; a pedal can be awkward when standing |
| Steady current, no pulse | Simple tacks, very short seams, or practiced operators | Heat control depends more on travel speed and manual current adjustment |
For occasional sheet-metal repairs, a lower-cost inverter TIG machine may be sufficient if it has stable low-amp output and the process controls you actually need. A machine with pulse is worth paying extra for when you will use repeatable pulsed beads; pulse is less valuable if most jobs are quick tacks. If you want to vary current without relying on a fixed pulse pattern, check whether the machine supports a compatible TIG foot pedal before buying.
Read the failure signs
A hole at the start often means you began on a thin edge, had a gap, or used too much peak current. Tack first, start on a thicker section if possible, and add current gradually. A bead that looks lumpy and sits high can indicate low peak current, a long arc, or travel that is too fast. A wide, discolored bead suggests excess heat or slow travel; on stainless, heavy discoloration can also mean poor shielding or no backing purge where one is needed.
Practice on offcuts of the same thickness and joint type. Make several short beads, record peak current, background percentage, frequency, and duty cycle, then keep the settings that produce consistent fusion without a growing heat-affected zone. Use a properly rated welding helmet, gloves, and protective clothing; thin metal does not make the arc, hot edges, or UV exposure any less hazardous.