TIG Welding Amp Chart: Settings by Metal Thickness

A beginner lays two beads on .065-inch stainless tubing: one at 90 amps burns a hole straight through the joint, the next at 40 amps sits on top like a cold worm. The arc looked identical both times — the only difference was a number on the dial that nobody had taught him how to choose.

Why Amperage Is the Single Most Important TIG Setting

A TIG amp chart is a lookup table that matches your metal type and thickness to a recommended starting amperage, so you can set the dial before you ever strike an arc. That single number on the machine matters more than any other setting in gas tungsten arc welding (GTAW), because amperage decides how much metal melts, how deep it penetrates, how the bead finishes, and how much your part distorts. Get it right and the puddle practically runs itself. Get it wrong and no amount of hand skill can rescue the weld.

TIG Is a Constant-Current Process

Most TIG machines output constant current, which means the power source holds a set amperage steady no matter how much the arc voltage wiggles during the weld. This is the key to understanding the whole chart. In plain language:

• Amperage is the volume of electrons flowing across the arc. It is the primary variable you control, either by turning the dial or pressing the foot pedal, and it is what actually melts the tungsten, base metal, and filler.
• Voltage is the electrical “pressure” of the arc. On a constant-current TIG machine you do not set it directly; it rises and falls with arc length.
• Arc length is the gap between the tungsten tip and the puddle. Stretch it and voltage climbs, spreading more heat over a wider area. Squeeze it down and the heat concentrates.

Because heat input rises with amperage and falls as you travel faster, the amps you choose set the ceiling on everything else. Crank the heat up and thin sheet pulls out of square, stainless tubing sugars on the back side, and the crater at the end of the bead freezes into a crack. Turn it down too far and the puddle sits on top of the joint instead of tying in, giving you cold lap, a towering stack of filler, and a weld that looks strong but isn’t fused. Excessive current also erodes the tungsten tip into a ball or a spike, and a contaminated electrode spits particles straight into your puddle. Poorly cleaned or dirty material makes it worse by destabilizing the arc and reducing the effective heat reaching the joint.

The Rule Everyone Starts With

The most widely taught starting point for mild steel is the 1 amp per 0.001 inch rule: a 0.063-inch plate wants roughly 60 amps, a 0.125-inch plate roughly 120 to 125 amps, and quarter-inch plate somewhere around 200 to 250 amps depending on joint design. It is only a heuristic, but it gets the dial into the right neighborhood fast, and every adjustment that follows — material, joint geometry, position, fixturing — stacks on top of it rather than replacing it.

Watch the puddle and you will see the truth of this immediately. A properly set arc lays a fluid, oxide-skinned pool about two to two-and-a-half times the filler rod diameter wide, wetting into the edges rather than climbing on top of them. Too hot, and the puddle goes mirror-flat and swallows the joint; too cold, and it balls up and drags. That observation — not the number on the dial — is the real decision-maker, and it is the skill the rest of this article is built to speed up.

It is also worth seeing the principle from the other side of the industry. Processes that regulate heat differently, such as the Advantages of Stick Welding: Why SMAW Still Wins, tolerate sloppier amperage choices because the stick electrode’s flux coating forgives more variation. TIG offers far finer control, but it demands far finer choices, which is exactly why a reliable amperage chart is worth keeping next to the machine.

Why the Chart Is a Starting Point, Not an Answer

No chart can see your joint. It does not know whether you are welding a flat butt joint or an overhead fillet, whether the part is clamped to a steel table that sucks heat away, whether the tubing is back-purged, or how fast your hands actually move. On aluminum, the numbers drift further still because the metal conducts heat so aggressively that the puddle races ahead of the arc; if you plan to work with it, our Aluminum MIG Welding: The Complete Practical Guide covers the same heat-management logic from the wire-fed side. Higher currents also generate more welding fume and ultraviolet output, so fume control scales with your settings, as NIOSH’s welding safety guidance emphasizes.

Use the chart value as your opening bid. Tack the joint, press the pedal, watch the puddle wet in, and adjust in small 5 to 10 amp steps until the fusion and bead profile look right. That loop — chart, arc, observe, adjust — is the working habit behind every number in the tables that follow, and it is what turns a printed reference into a setting you can trust on real material.

The 1 Amp per 0.001 Inch Rule Explained

Every amp chart in the world is really a dressed-up version of one simple heuristic: one amp of welding current for every thousandth of an inch of material thickness. Expressed as a formula, it is amperage = thickness in inches × 1,000. That is where the name comes from — 0.001 inch, one amp.

The rule is not a law of physics. It is a shop-floor shortcut that survived because it lands close enough to a workable setting on the first try, which is exactly what you want when you are standing at the machine with a torch in your hand and no time to derive anything. Instead of guessing, you measure, multiply, set the dial, and then let the puddle tell you whether to move.

Worked Examples: From Dial Setting to Puddle

Run a caliper or a thickness gauge over the metal, convert to thousandths, and multiply. Some common examples:

Thickness	Decimal (in)	Rule Value	Typical Starting Point
22 gauge sheet	0.030	30 A	25–35 A
16 gauge tube	0.063	63 A	55–70 A
1/8 in plate	0.125	125 A	110–135 A
3/16 in plate	0.187	187 A	150–190 A
1/4 in plate	0.250	250 A	200–250 A

Notice the last row. At 0.250 inch the pure math hands you 250 amps, but most welders land at 200 to 230 for a butt joint in flat position. Why? Because the rule quietly assumes a plain butt joint, good fit-up, steel, and a torch with plenty of cooling margin. When one of those assumptions breaks, the number adjusts.

There is also a metric version of the same idea: roughly one amp per 0.025 mm of thickness — commonly rounded to one amp per 0.25 mm, since shops tend to think in quarter-millimeter steps. A 1.5 mm sheet therefore lands around 60 to 75 amps, which matches the inch-based 0.063 result almost exactly. Both systems are describing the same puddle.

Adjustments That Stack on Top of the Rule

Think of the chart value as the base number, then add or subtract for the conditions in front of you:

• Material type. Steel follows the rule most closely. Aluminum typically needs about 20–30% more amperage than steel of equal thickness because it pulls heat away from the arc so fast. Prepping and cleaning aluminum properly matters just as much as the number, which is why guides like Aluminum Cleaner for Welding: How to Prep Aluminum Right are worth reading before you strike an arc.
• Joint geometry. Fillet and lap joints on heavier material demand more amps than open-root butt joints, because two members are absorbing heat instead of one. Corner joints sit at the low end — the edge melts before you can add much current.
• Welding position. Flat is your reference. Vertical-up and overhead usually mean dropping 10–15% and slowing your travel, since gravity works against puddle control.
• Heat-sinking fixtures. A copper backing bar, a heavy fixture plate, or clamping to a big weldment steals heat from the joint. Compensate by adding amps — sometimes 10–20% — or by slowing down.
• Mass and heat limits. Thin-wall tubing of the same thickness as plate needs fewer amps, because there is nowhere for the heat to go. And a small air-cooled 9-series torch has a hard ceiling well below what a water-cooled 20-series can sustain, no matter what the chart says.

Fit-up deserves special mention. A gap in a butt joint acts like a heat sink made of air: the arc has to bridge it, so you either close the gap or raise the amps and slow down. Conversely, a tight, well-tacked joint lets you run at the lower end of the range and keep distortion down.

The practical workflow is straightforward. Measure, calculate, set the dial, then add or subtract for material, joint, position, and fixturing. Lay a test bead on scrap of the same thickness and alloy, look at puddle width — a good target is roughly two to two-and-a-half times the filler rod diameter — and fine-tune in five to ten amp steps from there. The chart gets you close; the puddle gets you right.

TIG Amp Chart for Mild Steel and Stainless Steel

Steel is where most welders build their confidence, and it is also where a printed TIG amp chart earns its keep. Mild steel and stainless behave similarly enough to share one table, but not so similarly that you can ignore the differences. Use the numbers below as your cold-start setting for a clean butt joint in flat position, then let the puddle tell you whether to move up or down.

Starting Amperage by Thickness

DCEN (electrode negative) is the normal polarity for steel, usually with a 2% lanthanated or ceriated tungsten. The chart assumes argon shielding, clean mill-free surface, and no fixturing that sucks heat out of the joint.

Thickness	Mild Steel (A)	Stainless (A)	Tungsten Dia.	Filler Rod Dia.
22 ga (0.030 in / 0.8 mm)	40–55	35–50	1/16 in	0.030–1/16 in
18 ga (0.048 in / 1.2 mm)	55–75	50–70	1/16 in	1/16 in
16 ga (0.063 in / 1.6 mm)	60–80	55–75	1/16 or 3/32 in	1/16–3/32 in
14 ga (0.075 in / 1.9 mm)	75–95	70–90	3/32 in	3/32 in
1/8 in (0.125 in / 3.2 mm)	110–130	100–125	3/32 in	3/32 in
3/16 in (0.187 in / 4.8 mm)	140–170	130–160	3/32 or 1/8 in	3/32–1/8 in
1/4 in (0.250 in / 6.4 mm)	180–220	170–210	1/8 in	1/8 in
Over 1/4 in	220–280	200–260	5/32 or 1/8 in	3/16 in

Notice how closely this tracks the one-amp-per-thousandth rule from earlier: 1/16-inch (0.063 in) plate lands at 60–80 A, and 1/8-inch (0.125 in) lands at 110–130 A. The stainless column sits roughly 5 to 10 percent lower across the board, which is deliberate rather than conservative fussiness.

Why Stainless Wants Cooler, Faster Settings

Stainless actually conducts heat less readily than mild steel, which means the heat stays concentrated where the arc is instead of racing off into the surrounding plate. On paper that should let you weld hotter. In practice it works the other way, because stainless is chemically fussy about the heat it does absorb.

Keep stainless in the roughly 800–1,600°F range for long and chromium from the alloy migrates to grain boundaries, a process called carbide precipitation that robs the metal of corrosion resistance next to the weld. The fixes are predictable: run the lower end of the amperage column, travel a bit faster so the arc dwells for less time, keep interpass temperature reasonable, and accept a slightly narrower bead instead of stacking extra passes you do not need. Precision joint work like this is the bread and butter of aerospace TIG welding, where heat input is tracked almost as carefully as the weld itself.

The other stainless-specific hazard is sugaring. On tube and pipe root passes, the back side of the weld oxidizes into a rough, gray, cavitied crust when oxygen reaches the hot metal. That is not a cosmetic problem; it is a corrosion and fatigue starter. Argon back-purge is required on stainless tube root passes, meaning you fill the inside of the pipe with argon and hold a low flow until the weld is finished. No purge, no root pass, regardless of what the front side looks like.

Reading the Chart in Practice

Set the dial to the chart value, tack the joint, then watch puddle width rather than the readout. On a butt joint the puddle should wet out to roughly two to two and a half times your filler rod diameter. If it sits as a tight bead that will not spread, you are cold. If the edges keep creeping away from the arc and theBacking starts glowing, you are hot. Move in 5 to 10 amp steps, and remember that a copper fixture clamped against the joint can steal enough heat to justify an extra 10–15 A, while a joint with an open gap needs less metal melted and sometimes fewer amps than the chart suggests.

One last habit worth building: keep a small notebook of settings that worked. The chart gets you close on the first try, but the number that actually belongs to your machine, your torch, your tungsten, and your scrap pile is the one you proved yourself. Steel is forgiving enough to teach you quickly, which is part of why it remains the best practice material before you move on to aluminum’s AC settings.

TIG Amp Chart for Aluminum (AC Settings)

The neat amp-per-thousandth rule that works on steel falls apart on aluminum. Amperages run noticeably higher for the same thickness, and the machine needs a completely different mode. Understanding why that happens is the difference between fighting the metal and working with it.

Why Aluminum Breaks the Simple Rule

Two physical properties sabotage the math. First is thermal conductivity: aluminum moves heat away from the weld zone roughly five times faster than steel. Strike an arc and the surrounding material wicks energy away like a giant heat sink, so you need to pour in more amperage just to get a puddle started.

Second is the oxide layer. Aluminum forms a tough, transparent skin of aluminum oxide that melts near 3,700°F (2,040°C), while the aluminum underneath melts at about 1,220°F (660°C). The oxide is roughly three times more stubborn than the base metal. Heat the material alone and the oxide stays solid while the aluminum beneath turns to liquid and collapses. The arc has to shear that skin off before a puddle can form cleanly.

Why AC Is Non-Negotiable

Alternating current solves the oxide problem automatically. On the electrode-positive half of each cycle, electrons blast off the workpiece surface and shear the oxide away. That is the cleaning action. On the electrode-negative half, heat concentrates into the base metal and drives penetration. Run DC on aluminum and it either fails to clean or burns a hole, which is why AC is the default. Modern inverter machines let you tune that balance rather than accept whatever the sine wave hands you.

The Aluminum TIG Amp Chart

Use these as starting points for clean, properly fitted aluminum in the flat position. Everything else — joint type, position, mass, preheat — adjusts from here.

Thickness	Starting Amperage	Tungsten	Filler Rod
0.063 in (1.6 mm)	60–80 A	1/16 in	1/16 in
1/8 in (3.2 mm)	110–140 A	3/32 in	3/32 in
3/16 in (4.8 mm)	140–180 A	3/32–1/8 in	3/32–1/8 in
1/4 in (6.4 mm)	180–250 A	1/8 in	1/8 in

The numbers climb quickly. A quarter-inch of aluminum needs roughly double the amperage of a quarter-inch of stainless, and on AC the machine is only delivering useful penetration current for part of each cycle. That is a lot of heat to manage.

AC Balance: Cleaning vs. Penetration

The balance control sets the ratio of electrode-positive (cleaning) time to electrode-negative (penetration) time. On most modern machines it reads as a percentage of EN. Around 70% EN gives a strong, deep, narrow puddle with decent cleaning, and it is the classic default on a square-wave machine. Push to 80–85% EN and penetration tightens further, but you are asking less of the arc to break up stubborn oxide — great for heavy castings, risky on dirty metal. Drop to 50–60% EN when you need aggressive cleaning on heavily oxidized or poorly prepped stock, at the cost of a wider, shallower puddle and a hotter tungsten.

Frequency Narrows and Focuses the Arc

AC frequency changes the character of the arc entirely. Around 60 Hz, the arc spreads wide and soft, which helps when you want broad cleaning. Push to 120 Hz, 200 Hz, or more on premium inverters and the arc constricts into a tight, focused cone. A narrow arc concentrates heat exactly where you aim it, which is invaluable on thin aluminum and near edges that want to wash away. Higher frequency also stabilizes a jumpy AC arc without ballooning the heat-affected zone.

Gas Lens and Flow for Aluminum

Aluminum rewards a gas lens cup. The lens produces a smoother, more laminar argon stream that shields the wide AC puddle better than a standard collet body. Typical argon flow is 15–20 CFH with a standard cup, and you can push toward 20–30 CFH with a large gas lens and bigger cup, especially out of position or on thick material where the arc runs long. Too much flow invites turbulence that pulls air into the shielding envelope.

Thin Aluminum: Pedal and Pulse Technique

Thin aluminum punishes hesitation. You need amps high enough to puddle fast, then you must back off immediately or the edge collapses. This is where the foot pedal earns its keep. Set the machine higher than you think — 90–100 A for 0.063 in is typical — then use the pedal to ramp in, form the puddle, dab the rod, and feather back.

Pulse makes it easier still. A slow pulse around 1–2 Hz with a base of roughly 40% of peak lets the puddle freeze momentarily between peaks, preventing the runaway heat that opens a hole. Travel speed matters too: as amperage rises, travel speed must rise with it, or you will either wash the edge away or leave a cold, lumpy bead.

Preheat for Cast and Thick Aluminum

Cast aluminum is a heat sink in the worst way — porous, often dirty, and unpredictable. Thick sections above roughly 3/8 in also demand more heat than a single arc comfortably delivers. Preheat both to around 250–300°F (120–150°C). A quick pass with a torch or heat gun raises the baseline so the arc does not fight the mass, and it helps drive out moisture that causes porosity. Temperature crayons beat guessing. On marine or structural work the same principles scale up; our guide to aluminum boat welding walks through those heavier joint scenarios.

The takeaway: aluminum amps run higher, the machine lives on AC, and the real skill is managing heat that refuses to stay put. Set your starting number, watch the puddle, and let the pedal do the fine-tuning.

Choosing Tungsten Electrode Size, Filler Rod, and Gas Flow

The number on the dial only works if the hardware around it matches. An electrode that is too thin for the current balls up, spits, and drops tungsten inclusions into the puddle. A rod that is oversized chills the joint faster than the arc can compensate. Gas set at the wrong flow either starves the weld or tears turbulence into the shield. Getting this layer right before you strike an arc is what keeps the chart values honest.

Tungsten Diameter vs. Amperage Range

Each tungsten diameter has a current window where it stays stable. Push past the top and the tip overheats; drop below the bottom and the arc becomes erratic. The common mapping looks like this:

Tungsten diameter	Practical amperage range	Typical work
1/16 in (1.6 mm)	0–80 A	Thin sheet, tubing, autogenous tack work
3/32 in (2.4 mm)	40–150 A	The widest common range, especially in lanthanated or ceriated grades
1/8 in (3.2 mm)	125–250 A	Plate, structural fillets, heavier aluminum
5/32 in (4.0 mm)	160–500 A	Heavy sections, machine work, high-output setups

If you own one type of tungsten, 3/32 in lanthanated blue covers most shop work from about 40 to 150 amps in a single electrode. Step up to 1/8 in once you are consistently welding 1/4 in plate or running sustained AC on aluminum.

Preparation matters as much as size. On DC, grind the tip to a point with a dedicated diamond wheel, with grinding marks running lengthwise, parallel to the electrode axis. Longitudinal grooves let the arc start where you aimed it; circumferential marks make the arc wander and wander, spinning around the tip instead of sitting still. On AC aluminum, most welders still ball the tip slightly, though ground-point electrodes work on modern AC inverts. Stickout should be short at high amps (roughly 1/8 to 3/16 in, which focuses the arc and keeps gas coverage tight) and longer on thin material where you need to see the puddle.

Electrode contamination almost always traces back to four habits: dipping the tip in the puddle, striking the arc off the joint, pulling too long an arc, or running more current than the electrode diameter can carry. Each one invites tungsten spitting and, with it, porosity-like defects that fail inspection.

Filler Rod Sizing

The filler diameter should roughly match the thickness of the joint being welded, or sit slightly under it. A rod much larger than the joint drags heat out of the puddle and forces you to raise the amps; a rod too fine forces constant dipping and overheats the arc area. Practical pairings:

• 0.030–0.063 in sheet and thin tubing → 0.030–1/16 in rod
• 1/8 in plate → 1/16 in rod
• 3/16–1/4 in plate → 3/32 in rod
• 3/8 in and heavier → 1/8 in rod

For rod selection across materials and positions, see our All Position Welding Rod Guide: Types, Uses & Tips, which covers how filler classification changes with joint position.

Argon Flow, Cup Size, and Gas Lens

Typical argon flow is 15–20 CFH through a standard #8 cup, adjusted upward for drafts and larger cups. A gas lens running 20–30 CFH gives a wider, calmer column of gas that lets you extend the stickout and still keep the puddle shielded. Cup size and flow scale together: a #12 or #16 needs noticeably more gas than a #5. More is not automatically better. Excessive flow pulls air in around the nozzle and creates a turbulent, oxygen-contaminated shield, which shows up as porosity and sugaring on stainless.

Torch Current Capacity and Cooling

Your torch is the ceiling on every setting you dial in. Small air-cooled 9-series torches are light and maneuverable but are not rated for unlimited 100% duty cycle; they are comfortable for thin material and intermittent tacks, not an afternoon of continuous 200 A beads. Above roughly 150 amps of sustained output, a water-cooled torch becomes the sensible choice, with water-cooled 20-series torches handling sustained work in the 180–350 A range without the handle or cable cooking. A quick rule: if your hand gets hot before the puddle does, your torch is the limiting factor, not your technique. For torch bodies, cables, and regulator choices, our Airgas Welding Equipment Guide: What You Need to Know walks through the hardware tradeoffs.

How Joint Type, Position, and Material Condition Change the Numbers

An amp chart gives you one number per thickness, but the chart has no way of knowing that your joint has a 1/16-inch gap, that you’re welding it vertical-up off a ladder, or that the part is clamped to a massive steel fixture. Those variables can swing the correct amperage by 20% or more in either direction. Learning to read the joint before you set the dial is what separates a chart-follower from a welder who actually controls the puddle.

Joint Geometry: Not All Joints Draw Heat the Same Way

The same plate thickness demands different settings depending on how the pieces meet:

• Butt joint, flat: the baseline case. Full penetration with minimal restraint. Use the chart value as written.
• Lap joint: two layers of metal sit under the arc, and the lower sheet acts as a heat sink on one side. Start at the chart value and nudge up 5–10 A if the top edge isn’t wetting in.
• T-fillet: the vertical member hogs heat away from the weld zone. Fillets on 1/8-inch plate often need the chart value or slightly more, plus a tighter arc on the joint root.
• Corner joint: the thinnest, most vulnerable configuration because both edges are free to melt back. Drop 5–10 A below the chart value and slow down at the edges to avoid burn-through.

Fit-up matters just as much. An open root gap on pipe concentrates the arc on two thin edge faces, so it requires lower amps with faster travel to prevent dropout. A tight, well-fitted butt with no gap can take the full chart value, sometimes more on heavier plate where you’re chasing penetration.

Position: Subtract 10–15% Out of Position

Gravity works against you the moment the weld isn’t flat. Overhead and vertical-up puddles want to sag or run, so most welders drop amperage roughly 10–15% from the flat setting and let travel speed do the rest. A 1/8-inch fillet that runs beautifully at 120 A flat will typically behave better at 100–110 A overhead. Position also changes filler cadence: feed the rod more deliberately and keep the arc pointed slightly upward in vertical-up to pin the puddle. This is exactly why all-position welding rod selection gets its own guide — electrode choice and amperage adjustments work together here.

Heat Sinks, Fixtures, and Material Mass

Clamp a coupon to a copper chill block and the copper will pull heat away from the joint almost as fast as you put it in. In that situation, expect to increase amps 10–20% to keep the puddle fluid. The same logic applies to any heavy fixture, tack-welded jig, or large part where the surrounding metal acts as a radiator.

Material mass cuts the other way. Small-diameter tubing has far less heat-sinking mass than plate of the same wall thickness, because there’s simply less metal to absorb and spread the energy. Two pieces of 0.065-inch tubing welded at 60 A can be fine, while a 0.065-inch patch on a large flat panel may need slightly more to keep moving. Always weld a coupon of the same alloy and thickness before committing to the real part, and keep a clean, oxide-free surface — mill scale, oil, and grinding residue destabilize the arc and reduce effective amperage delivered to the joint.

Thickness Transitions

When a joint meets two different gauges, you can’t satisfy both with one setting. Set the dial for the thinner member, then let arc length and travel speed favor the heavier side: dwell briefly on the thick plate, keep the arc tight and moving over the thin edge. Hand-positioned heat control, not the dial, closes the gap.

Three Practical Scenarios

Scenario	Chart Value	Adjusted Setting	Why
1/8 in mild steel T-fillet, flat	110 A	115–120 A	Vertical leg sinks heat
1/8 in stainless overhead, gap open root	110 A	90–95 A	−15% for position, faster travel to stop dropout
0.063 in aluminum on copper backing	70 A	78–84 A	+10–20% to offset chill block
1/4 in plate clamped to heavy jig	200 A	215–230 A	Fixture draws heat from weld zone

Notice the pattern: the chart value is still the anchor. Joint type, position, fit-up, and surrounding mass only nudge it. Once you learn to spot those four conditions before you strike an arc, every setting becomes a reasoned decision instead of a guess — and your first bead, not your third, lands where you want it.

Reading Your Machine: Duty Cycle, Balance, Pulse, and Pedal Control

An amp chart hands you a number, like 110 amps for 1/8-inch aluminum. Your machine decides how that number actually reaches the joint. Two welders can set the same dial position and get very different results because one unit is running at full output on 230-volt input while the other is sagging on a long 120-volt extension cord. Knowing how to read the nameplate, the knobs, and the pedal turns the chart from a guess into a repeatable setting.

Duty Cycle and Input Power

Duty cycle describes how long a machine can weld continuously at a stated amperage within a defined 10-minute period, at a stated ambient temperature. A rating of 60 percent at 150 amps means six minutes of welding out of every ten before the thermal overload kicks in, followed by four minutes of cooling. Push past it repeatedly and you are not welding faster, you are shortening the machine’s life.

Read the whole rating plate, because output changes with input. A compact TIG rated 160 amps at 60 percent on 230-volt input may only manage 100 amps at 20 percent on 120 volts. Set your chart value first, then confirm the machine can actually hold it for the thickness you are about to run.

Transformer vs. Inverter, and How the Arc Starts

Older transformer machines are heavy, draw more input power, and are usually AC-only, which makes them simple and dependable for aluminum but clumsy for stainless and mild steel. Inverter machines are lighter, more efficient, and hold a stable arc much lower on the dial, which matters when 40 amps has to behave as calmly as 200. Most modern inverter TIG welders are AC/DC, giving you DC for steel, stainless and copper, and AC for aluminum and magnesium.

Starting the arc is a second choice. High-frequency start jumps the gap without touching the tungsten, so nothing contaminates the electrode and the arc is clean from the first millisecond. Lift-arc requires the tungsten to touch the joint and pull away, which risks a bitten-off tip, but it is sometimes preferred where stray radio energy from high frequency could upset nearby electronics.

The Foot Pedal: Your Real Amperage Control

The dial sets a maximum. The foot pedal lets you vary current from near zero up to that maximum, continuously, mid-weld. That is why a single chart value is really a curve in practice:

• Start at roughly 60–70 percent of the set amps to establish a puddle without gouging a cold, thick tack.
• Roll to the full set value once the puddle is established and traveling.
• Back off at the end so the crater fills instead of shrinking into a crack.

Downslope performs that final taper automatically, ramping current down over a set number of seconds, while post-flow keeps argon covering the crater after the arc is gone. On aluminum, where crater cracks are a constant nuisance, a synchronized combination of downslope, crater timer, and a light pedal release at the end is the standard fix.

Pulse: Full Penetration, Less Overall Heat

Pulsing alternates between a peak amperage that drives penetration and a base amperage that lets the puddle rest. A peak of 100 amps with a base of 40 amps cycling at 1–2 Hz gives you the penetration of a 100-amp arc at a fraction of that average heat. Less heat input means less distortion on thin sheet, an easier puddle to chase out of position, and the familiar stacked-dime appearance.

Setting	Typical Starting Point	What It Controls
Peak amps	Chart value (e.g., 100 A)	Penetration during the hot half of the cycle
Base amps	20–50% of peak (e.g., 40 A)	How much the puddle cools between peaks
Pulse rate	1–2 Hz manual rhythm	Travel pacing; higher rates narrow the bead
Pulse on/off time	Balanced 50/50	Ratio of heating to cooling per cycle

Aluminum is where these controls pay for themselves, since a slow, controlled arc and a proper end-of-weld taper protect you from cracking in a sensitive alloy. It is also where prep decides how the arc behaves, which is why Aluminum Cleaner for Welding: How to Prep Aluminum Right is worth reading before you touch the machine settings. Cast components like wheels are another good case for pulse: the mass changes constantly as you move, and a pulsed arc gives the heat somewhere to go between strokes, as covered in Alloy Wheel Welding: A Comprehensive Guide to Safe and Effective Aluminum Wheel Repair.

Balance and Frequency Knobs

On an AC machine, balance splits the cycle between cleaning (electrode positive) and penetration (electrode negative), while frequency tightens or widens the arc cone. A tighter cone concentrates heat for thicker sections; a wider one spreads it for thin, delicate work. These do not change the amp chart, but they change what those amps do, so jot down your balance and frequency alongside your amperage whenever you record a setting that works.

Common Amp-Setting Mistakes and Troubleshooting the Puddle

The chart gives you a number; the puddle tells you whether it works. Even when you start exactly where a tig welding amp chart says you should, three variables quietly move the effective heat: tungsten preparation, arc stand-off, and how fast you move. Tracing a bad bead to one cause is what turns a table into real control at the pedal.

The Order of Operations: What to Check First

When a weld looks wrong, resist the urge to twist the dial first. Amperage is the easiest setting to change, which makes it the most common wrong answer. Check the variables in this order:

1. Tungsten preparation and stickout. Grind the electrode parallel to its length, not in a round cone, with the grind marks running lengthwise so the arc has a straight path. A point roughly twice the electrode diameter is solid geometry. A blunted, balled, or chipped tip makes the arc wander before you touch the amps.
2. Gas coverage. Look for drafts, a loose cup, a kinked hose, or a flow rate high enough to trip turbulence. Cup size matters too: too large restricts access and wastes gas, too small will not shield the puddle.
3. Amperage. Only now adjust the dial, and only in 5 to 10 amp increments while watching puddle width.
4. Travel speed, technique, and fit-up. A gap, a heavy fixture, or a fast hand can make correct amperage look wrong.

Symptom, Cause, Fix: Puddle Diagnostics

Symptom	Likely cause	Fix
Burn-through or a hole opening up	Amps too high, travel too slow, heat piled into one spot	Drop 5–10 A, speed up, or ease off the pedal; on thin tubing add tacks to spread heat
Cold lap; toes not tied in	Amps too low, travel too fast, mill scale or oil insulating the arc	Raise 5–10 A, slow down, clean the base metal
Excessive convexity or towering bead	Too cold, or more filler than the puddle absorbs	Add amps and feed rod only as fast as the puddle takes it
Undercut along the toes	Too hot, too fast, long arc, or torch aimed at the joint edge	Reduce amperage slightly and keep the arc centered on the joint, not the edge
Tungsten spitting or a contaminated tip	Electrode touched the puddle or rod; arc too long	Stop and regrind or replace — arcing contamination clean is unreliable
Porosity, especially pinholes	Drafty air, oily or wet metal, aluminum oxide, damp rod	Block the draft, verify flow, wipe joint and rod; aluminum needs the same non-negotiable pre-weld cleaning described in Aluminum Cleaner for Welding: How to Prep Aluminum Right
Arc wandering off the joint	Wrong grind geometry, dirty tungsten, arc blow, or AC frequency too low	Regrind parallel to length, wipe the electrode, raise frequency for a tighter arc
Sugaring on the back side of stainless	No argon purge, a weak purge, or amps too high with slow travel	Purge the back side, lower amperage slightly, travel faster to limit heat
Crater crack at the stop	Arc stopped abruptly while the puddle was still shrinking	Use downslope and crater amps, or feather the pedal before breaking the arc

Arc Length: The Setting You Change Without Thinking

TIG is constant-current, so amperage stays where you set it regardless of arc length. Voltage does not: it climbs as the tungsten moves away, and arc power is amps times volts. A long arc therefore pumps more energy into the plate while spreading it wider, giving a broad, shallow puddle, more spatter, a hotter tungsten, and less penetration than the dial promised.

Hold the tip close, around 1/16 in for most work, and the same amperage delivers a narrow, deep, directed puddle. That is why two welders on identical settings get different results: arc length is a hidden amperage control, and the first thing a seasoned welder checks when a bead looks cold despite a correct dial reading. In critical work such as the procedures in Aerospace TIG Welding: Standards, Techniques, and Training, arc length discipline is a controlled variable, not a personal habit.

Crater Cracks: The Last Two Seconds

Most crater cracks come from stopping too abruptly. When the arc cuts out instantly, the last pool solidifies faster at its center than at its edges and tears under shrinkage stress; aluminum is especially unforgiving because it shrinks more as it solidifies. The fix is mechanical: set a downslope of one to two seconds and a crater amperage around 25 to 30 percent of peak, or feather the foot pedal down yourself. A final dab of rod while the arc still softens the puddle finishes the joint.

Build the loop deliberately: read the puddle, name the symptom, check tungsten and gas before touching the dial, then adjust in small increments. Soon you will predict what the next five amps do.

Safety, Fumes, and Standards Behind the Numbers

Every amp you dial up leaves the machine as three things at once: heat in the joint, radiation, and a plume of vaporized metal. That is why safety belongs in the same conversation as settings. The same dial that controls penetration also controls how much fume you breathe and how hard your eyes and skin work to keep it out.

More Amps, More Fume, More Radiation

Fume generation generally tracks arc energy. Higher amperage, hotter interpass temperatures, and slower travel all push more metal into the air. TIG is still the cleanest common arc process because the electrode is non-consumable and the argon shield carries no flux fumes, a stark contrast to high-fume work like carbon arc gouging. But “cleanest” is a relative term. Stainless, chrome-moly, nickel alloys, and any plated, galvanized, or painted surface all put oxides and alloying elements into the plume, and dirty or solvent-cleaned base metal adds more.

Radiation scales with current too. Higher amperage means more intense ultraviolet and infrared output that arc-burns exposed skin in minutes, flash-burns eyes, and degrades plastics and paint finishes across the shop. That is why welding screens go up around the table, not just as a courtesy to anyone walking past.

What OSHA Requires for Ventilation

Two OSHA rules cover most of this work. For construction, 29 CFR 1926.353 requires mechanical ventilation sufficient to keep welding fumes and gases within safe limits whenever natural ventilation cannot do the job, with stricter requirements in enclosed and confined spaces. General industry has the parallel rule in 29 CFR 1910.252. Both forbid a common shop shortcut: blowing a fan horizontally across the arc toward the welder, which only drives the plume into the breathing zone instead of exhausting it. OSHA’s welding fact sheet summarizes the ventilation, PPE, and fire-prevention expectations in plain language.

When ventilation cannot hold exposure below the limits, the fallback is a formal respiratory protection program, not a dust mask grabbed off the shelf.

Hexavalent Chromium: The Stainless Trap

This is the TIG-specific exposure that catches people off guard. Welding stainless steel and other chromium-bearing alloys can generate hexavalent chromium in the fume. OSHA’s general industry standard sets the permissible exposure limit at 5 µg/m³ as an 8-hour time-weighted average, with an action level of 2.5 µg/m³ that triggers exposure monitoring, medical surveillance, and written compliance programs. Higher amperage, preheat, and hot interpass conditions all increase Cr(VI) generation, so heat input has a direct health dimension. The same logic applies when welding corrosion-resistant alloys like Alloy 20 or duplex stainless. NIOSH welding guidance from the CDC reinforces the hierarchy: engineering controls and ventilation first, respirators as backup.

Eye, Skin, and Electrical Safety

Arc radiation protection scales with amperage as well. Higher currents demand darker filter lenses; OSHA’s filter-shade guidance generally places typical TIG work in the shade 8 to 12 range depending on current and AC or DC mode, with AC work often pushing toward the darker end. Auto-darkening helmets need sensitivity, delay, and shade dialed in rather than left on a factory default. Nearby workers need the same protection, which is what welding curtains and fixed screens are actually for.

High-frequency start introduces one more hazard: electromagnetic interference with cardiac devices. Pacemaker and defibrillator wearers should get physician clearance before welding and keep at least 10 feet between themselves and any high-frequency equipment. Lift-arc or scratch-start modes remove the HF concern entirely. Aerospace TIG welding procedures treat these electrical and documentation requirements as routine, which is a good model for any shop working to a higher bar.

ANSI Z49.1 and the Control Hierarchy

ANSI Z49.1, Safety in Welding, Cutting and Allied Processes, is the consensus standard behind most of this. It covers ventilation, eye and face protection, electrical safety, fire prevention, and compressed gas handling. It is not law on its own, but OSHA references it in compliance guidance and most shop safety programs are built on it.

The operating principle is worth building into muscle memory: the amp chart sets your arc, but the safety plan scales with it. Turn the current up, and ventilation, exposure controls, and PPE need to come up with it.

Practical Tips, Quick Reference, and Conclusion

Every chart, rule of thumb, and table in this article only gets you to the starting line. The arc itself does the teaching. The best habit you can build as a TIG welder is treating each recommended number as a hypothesis to test rather than a command to obey, then letting the puddle confirm or overrule it. The workflow below is the same one experienced welders run whether they are setting up a 200 A inverter machine or nursing a vintage transformer rig through thin stainless.

A Seven-Step Dialing-In Workflow

1. Set the dial to the chart value. Look up your material, thickness, and joint, then dial in the recommended starting amperage before you strike an arc. Do not guess.
2. Tack first. Put four small tacks on a scrap piece of the exact same alloy and thickness. Tacks are cheap; rework is not.
3. Watch the puddle, not the dial. A well-fed puddle wets out to roughly 2 to 2.5 times the diameter of your filler rod. If it sits narrow and humps up, you are cold. If it turns mirror-bright and drops through, you are hot.
4. Adjust in small increments. Move in 5 to 10 A steps, not 30 A swings. TIG rewards fine control, and a 5 A change is often the difference between a stacked-dime bead and a cold worm.
5. Cross-check travel speed. If the settings are right but the bead still looks wrong, the problem is usually how fast you are moving or how long you are lingering.
6. Run a full bead on scrap of the same thickness and alloy before touching the real joint, including the same fixturing and backing wherever possible.
7. Write it down. Log machine, tungsten, gas flow, amps, pedal behavior, and result for every setup that works.

Quick-Reference Recap

Thickness	Mild Steel (DCEN)	Stainless (DCEN)	Aluminum (AC)	Tungsten	Filler Rod
22 ga / 0.030 in	30–40 A	25–35 A	30–45 A	1/16 in	0.035–1/16 in
0.063 in	50–65 A	45–60 A	60–80 A	1/16–3/32 in	1/16 in
1/8 in	110–130 A	100–120 A	110–140 A	3/32 in	1/16–3/32 in
3/16 in	150–180 A	140–170 A	140–180 A	3/32–1/8 in	3/32 in
1/4 in	200–250 A	180–230 A	180–250 A	1/8 in	1/8 in

Read the table as a launch point, then apply the modifiers covered earlier: subtract 10 to 15 percent out of position, add amps on copper-backed joints, and stay conservative on heat-sensitive alloys. If you are pushing into high-amperage aluminum or structural work and want to see how professionals formalize these procedures, our guide to aerospace TIG welding shows what disciplined procedure control looks like. For vertical and overhead filler selection, the all-position welding rod guide fills in the gaps. Migrating from TIG to aluminum production work? See our aluminum MIG welding guide, and grab quality cylinders through an Airgas welding supplies buyer’s guide before your next project.

One last reminder: a TIG amp chart is a starting point, never a substitute for puddle observation. The metal in front of you is the final authority on whether the number on the dial was right. Start with the chart, trust the puddle, tune in small steps, and write down what works. Do that consistently and within a few months you will stop needing to look amperage up at all, because you will already know what 1/8-inch aluminum and 0.049-inch stainless tubing feel like under your hand.

Frequently Asked Questions

What is the basic rule of thumb for TIG welding amperage?

For mild steel, start at about 1 amp per 0.001 inch (1 amp per 0.025 mm) of material thickness. So 1/8-inch plate starts near 125 amps, and 16-gauge (about 0.063 in) starts near 60–70 amps. Adjust from there based on joint type, position, and heat sinking.

Do I need more amps for aluminum than steel?

Yes. Aluminum conducts heat away from the puddle roughly five times faster than steel, so it usually needs about 20–30% more amperage at the same thickness, welded on AC with adequate cleaning action. Travel speed also has to increase to avoid melting the edges away.

Why does stainless steel need different settings than mild steel?

Stainless concentrates heat because of lower thermal conductivity, so many welders run slightly lower amps with faster travel to limit the heat-affected zone. On tubing, the root must be back-purged with argon to prevent sugaring, and excessive heat can cause sensitization and discoloration.

What tungsten size should I use for a given amperage?

A 1/16-inch tungsten suits roughly 0–80 amps, 3/32-inch covers about 40–150 amps, 1/8-inch handles 125–250 amps, and 5/32-inch is for 160–500 amps. For most shop work from sheet to 1/4-inch plate, a 3/32-inch 2% lanthanated tungsten is the versatile choice.

What happens if my amperage is too high or too low?

Too high causes burn-through, wide flat beads, undercut, excessive distortion, and crater cracks. Too low produces cold lumpy beads sitting on the surface, lack of fusion, and a wandering arc. Both conditions weaken the joint; adjust in 5–10 amp increments and let the puddle guide you.

How does the foot pedal change my amperage settings?

The pedal lets you vary current from nearly zero up to the maximum set on the machine dial. A common technique is to start at 60–70% of set amps for the tack and puddle start, rise to full set amps for travel, then taper off for crater fill.

Does pulse welding reduce the amps I need?

Pulsing alternates between a peak amperage and a lower base amperage, cutting average heat input without changing penetration at the peak. It does not replace proper base settings — you still set the peak value from the chart, then tune frequency and base amps (often 40–60% of peak) for control.

How accurate is a printed TIG amp chart?

It is accurate as a starting point, but real amps depend on joint design, position, travel speed, fit-up gaps, backing material, torch cooling, and your machine’s actual output. Always verify on scrap of the same alloy and thickness before welding the final part.