TIG amps by material thickness

Start points by material and thickness — the pedal does the rest.

Unlike MIG, where the machine holds voltage constant and wire speed sets the amps, a TIG torch delivers exactly the amperage you ask for. That makes amperage the first — and most argued-about — setting on every TIG job. Set it too low and you never establish a puddle; set it too high and you undercut, warp thin sheet, or drop a hole through it. The chart below gives starting windows for the three materials most shops actually weld, then explains the famous rule of thumb behind them and exactly where it fails.

TIG amperage chart: steel, stainless, aluminum

Steel and stainless windows assume argon shielding, a properly ground tungsten, and a joint you'd actually weld in one or two passes. The aluminum column is published chart cells, not a scaled steel rule. At 0.125" the cell is Miller’s section 8-3 butt start for 1/8" 6061: 90–120 A, with a T-joint at 100–125 A, a lap at 90–110 A, and a corner at 80–90 A, 1/8" 5356 filler, and 3/32" 2% ceriated tungsten. Lincoln’s Square Wave TIG 200 chart (L16988) lists 120–135 A for that same 1/8" thickness; this cell keeps the Miller butt row. The 0.062" cell is L16988’s 1/16" / 16 ga column, 75–85 A. The 0.187" cell is L16988’s 3/16" (4.8 mm) column, 165–195 A; the calculator’s exact hit for that cell is 188 mils. The 0.250" cell is the Harris/Lincoln 4043 GTAW sheet, 220–275 A. Cells marked “Nearest” are not published at that thickness: 0.030" uses the 24 ga (0.024") row, 25–35 A, and 0.093" uses the 0.090" row, 85–110 A. The shared tungsten and filler columns are the steel pairing; they are not the tungsten or filler named on the aluminum chart. Thin material needs less absolute amperage but tighter control, which is why a machine with a good foot pedal or torch-mounted amperage control matters more than raw output below 100 A. Our main calculator uses the same split: steel and stainless stay on the 1-amp-per-mil rule, 125 mils of aluminum returns the 90–120 A butt start, and any other aluminum thickness returns a published Lincoln row or the nearest one.

The 1-amp-per-0.001-inch rule

The most durable rule of thumb in TIG: 1 amp for every 0.001" of mild steel thickness. 0.062" steel wants about 60 A; 1/8" (0.125") wants about 125 A. It holds reasonably well for steel and stainless from roughly 0.030" to 0.125" — beyond that range, joint design, heat sinking, and travel speed start to dominate. It is a starting point, not a setting: the real technique is to pedal up to the high end of the range to establish the puddle quickly, then back off 20–30% to travel. Riding a constant 125 A the whole bead is how thin corners get blown out.

Where it breaks, deliberately: aluminum is not 1.5 amps per mil. Miller’s GTAW guidelines, section 8-3, start a 1/8" 6061 butt joint at 90–120 A on AC, and the calculator prints that row at 125 mils. Other aluminum thicknesses come from Lincoln’s published cells: L16988 for 24 ga through 3/16", and the 4043 GTAW sheet for 1/4", 3/8", and 1/2". A thickness between those cells shows the nearest published row and says so. It does not interpolate. Thin stainless is the opposite of a hotter rule: it holds heat, discolors, and warps fast, so stay at the bottom of the range or below and let the pedal do the restraint. The TIG tab’s stainless factor is 0.9, which is not Lincoln L16988’s stainless column. Both are written out on how to TIG weld stainless steel. And past 1/4" no simple rule survives — preheat to 200–300°F or the puddle freezes at the edges before fusion happens.

Published aluminum thickness limits by voltage are on what size welder for aluminum. The joint-by-joint 6061 starts, plus the Lincoln rows the calculator uses, are on how to weld aluminum. Sources: Miller GTAW guidelines, Lincoln Square Wave TIG 200 quick reference L16988, and the Harris/Lincoln 4043 GTAW sheet.

TIG amps for stainless steel

Stainless uses the lower windows in the chart: 20–30 A at 0.030 inch, 45–60 A at 0.062 inch, 95–115 A at 1/8 inch, and 180–220 A at 1/4 inch. The calculator applies a 0.9 factor for stainless, so start toward the bottom of the window and use the pedal for restraint. Thin stainless holds heat, discolors, and warps quickly; a lower start gives the puddle time to form without carrying excess heat through the rest of the bead. Those stainless windows are this page's chart guidance, not a Lincoln L16988 stainless column.

AC vs DC: which for which metal

DCEN (DC electrode negative) is the default for everything except aluminum and magnesium: steel, stainless, titanium, copper alloys, chromoly. About 70–80% of the arc heat lands on the workpiece, the tungsten stays cool and holds a sharp grind, and the bead is narrow and penetrating. AC exists for one reason: the oxide layer. Aluminum's oxide melts at over 3,600°F while the metal under it melts near 1,200°F — DCEN can't break it. The electrode-positive half of each AC cycle blasts the oxide off (cleaning action) while the electrode-negative half does the heating.

Modern inverter machines let you tune that balance. Start at 65–70% electrode negative with AC frequency at 100–120 Hz for a tight, focused arc on 0.062–0.125" material. If you see a wide sooty cleaning band and a balling tungsten, you're running too much electrode positive — shift the balance toward EN. Higher frequency narrows the arc cone and is handy on inside corners; lower frequency gives a wider, softer puddle for outside fillets.

Filler selection by material

Filler follows the base metal's family, not its thickness. Mild steel: ER70S-2 or ER70S-6 — the same wire chemistry MIG uses, in rod form; S-2 tolerates slightly dirtier surface metal. Stainless: ER308L for 304 base metal, ER316L for 316; always match or slightly over-alloy the filler to keep corrosion resistance. Aluminum: 4043 is the general-purpose, crack-resistant default; move to 5356 when you need higher as-welded strength or a color match after anodizing. Sizing is simple — filler diameter about equal to or one size larger than the tungsten, which is what the table above pairs up. On thin sheet, filler one size down from the tungsten keeps you from dumping cold rod into a small puddle.

Tungsten sizing and prep

1/16" lanthanated covers roughly 30–100 A DCEN, 3/32" covers 90–180 A, and 1/8" covers 150–250 A. Oversizing the tungsten is the classic beginner error — a too-big tungsten gives a wandering, hard-to-start arc at low amps. On AC for aluminum, tungsten runs hotter: step up one size from what the steel amperage would suggest and let the tip form a slight ball. Grind DCEN tungstens longitudinally (lines running away from the tip), never circumferentially — cross-grinding makes the arc wander. Use a dedicated grinding wheel for tungsten; thoriated dust is not something to share with your bench grinder.

Long beads and duty cycle

TIG amps tax a machine differently than MIG. A long bead near the top of a machine’s rating will run it up against its thermal limit. If you're planning production-length runs near the top of the chart, check the machine's real continuous capability with the duty cycle calculator before you commit to a fabrication schedule. And if you're costing out a TIG production job, the weld cost calculator handles filler, gas, and labor per joint.

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FAQ

Is 1 amp per 0.001 inch a good rule for TIG?

It's a fair starting point for steel and stainless in the 0.030"–0.125" range (30–125 A), with foot pedal control doing the real work: start high to establish the puddle, back off to travel. It is not the aluminum rule. Miller's GTAW guidelines, section 8-3, start 1/8 inch 6061 at 90–120 A for a butt joint. Thin stainless still warms fast and needs restraint.

What size tungsten for what amperage?

1/16" lanthanated covers roughly 30–100 A DCEN, 3/32" covers 90–180 A, and 1/8" covers 150–250 A. On AC for aluminum, tungsten runs hotter — step up one size (a 3/32" for jobs a 1/16" would do on steel) and ball the tip slightly with balanced AC.

Do I use AC or DC for TIG?

DCEN (DC electrode negative) for steel, stainless, and most other metals — the workpiece gets the heat and the tungsten stays sharp. AC only for aluminum and magnesium, where the electrode-positive half-cycle breaks up the tenacious oxide layer. Some inverters offer AC balance and frequency controls to tune that cleaning action.

What filler rod do I use for TIG?

Match the rod family to the base metal: ER70S-2 or ER70S-6 for mild steel, ER308L for 304 stainless (316L for 316), and 4043 as the general-purpose aluminum rod — switch to 5356 for higher strength or anodized-color match. Filler diameter is usually the same as or one size up from the tungsten.

How many amps for 1/8 inch aluminum TIG?

Miller's GTAW guidelines, section 8-3, list 90–120 A for a 1/8 inch 6061 butt joint, with 1/8 inch 5356 filler, 3/32 inch 2% ceriated tungsten, and argon at 15–20 CFH. The same table lists a T-joint at 100–125 A, a lap at 90–110 A, and a corner at 80–90 A. The calculator returns that butt row at 125 mils. Lincoln's Square Wave chart lists 120–135 A for 1/8 inch aluminum; this page keeps the Miller butt row.

What aluminum TIG amps does the calculator return besides 1/8 inch?

Exact published rows: 1/16 inch (62 mils) is 75–85 A on Lincoln's Square Wave TIG 200 chart L16988; 3/16 inch (188 mils) is 165–195 A on that same chart; 1/4 inch (250 mils) is 220–275 A on the Harris/Lincoln 4043 GTAW sheet. 3/32 inch entered as 94 mils is not a published row. The nearest published thickness is 0.090 inch, and that Lincoln cell is 85–110 A. The calculator labels that result as the nearest published row and does not interpolate.