What's inside
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Starting amperage for thin stainless steel
For thin stainless, begin around 30–40 amps for 0.5 mm sheet, 40–55 amps for 0.8 mm, and 55–75 amps for 1.2 mm. These are starting ranges, not fixed settings: joint fit, torch angle, travel speed, tungsten size, and how well the parts conduct heat all matter. A butt joint with a small, even gap needs less heat than a thick lap joint or a piece clamped to a heavy fixture.
Set the machine to DC electrode negative (DCEN), use a sharp tungsten, and make a short test bead on scrap of the same thickness. Increase current if the puddle is slow to form or the bead is tall and narrow. Reduce it if the edges melt away before you can move, or the puddle gets too wide. If the machine has a foot pedal or torch control, set a useful maximum and regulate heat as you weld; a machine with only a fixed setting demands steadier travel speed.
Practical starting settings
| Stainless thickness | Starting current | Filler rod | Typical tungsten |
|---|---|---|---|
| 0.5 mm (about 24 gauge) | 30–40 A | 0.8–1.0 mm | 1.0 mm |
| 0.8 mm (about 22 gauge) | 40–55 A | 1.0–1.2 mm | 1.0 or 1.6 mm |
| 1.2 mm (about 18 gauge) | 55–75 A | 1.2–1.6 mm | 1.6 mm |
These figures assume a short, controlled arc and a reasonably tight fit-up. They are useful starting points for flat or horizontal work, but overhead or awkward-position welding may call for less current. A small inverter TIG welder with adjustable output and a pedal is often easier to control on thin sheet than a large machine without fine adjustment. If you are shopping, compare the actual minimum amperage and control options on DC TIG welders with foot pedals, not just the advertised maximum output.
Fit-up and preparation matter as much as amps
Clean the weld zone with a dedicated stainless-steel brush or clean abrasive, and remove oil, paint, and adhesive. Keep tools used on stainless separate from tools used on carbon steel; embedded iron can rust and stain the finished surface. Solvent-cleaned metal must be fully dry before welding. Use clean gloves so you do not transfer grease back onto the joint.
Thin sheet magnifies fit-up problems. A gap that looks minor can open as the edges heat, leading to burn-through or a lumpy bead. Aim for close, consistent contact and tack the joint every few centimetres before welding between tacks. For a butt joint, a copper backing bar can support the edges and pull heat away, but it needs to sit tightly against the work. Clamps and a heavy fixture also reduce distortion, though they may draw heat out enough to slow puddle formation.
Gas, torch setup, and travel speed
Use argon shielding gas, commonly around 8–12 cubic feet per hour (CFH) with a suitable cup in a draft-free area. More flow is not automatically better: excessive flow can create turbulence that pulls air into the shield. Wind can ruin shielding even at a higher flow rate, so use a screen or move indoors. A small gas lens and larger cup can provide more consistent coverage when access allows.
Keep the arc short, roughly the diameter of the tungsten, and hold the torch at a modest angle. A long arc spreads heat, widens the bead, and increases the chance of oxidation. Move steadily once the puddle forms; lingering in one spot is a common cause of burn-through. Add small, frequent dabs of filler rather than large deposits. Filler helps bridge a close joint and can make the bead less prone to cracking, but it will not fix a badly uneven gap.
For very thin sheet, pulsed TIG can make heat input easier to manage by alternating between a higher peak current and a lower background current. It is a useful control, not a substitute for good fit-up and consistent motion. A basic machine without pulse can still weld thin stainless well. If you want to compare machines, check low-end amperage control and pulse functions before paying extra for features you may rarely use.
Read the bead and adjust one thing at a time
Burn-through or sagging edges: lower the peak current by 5–10 amps, move faster, close the gap, or add backing. Change one factor at a time so you can tell what helped. A gap or a pause at the edge is often the real cause, not simply an overly high panel setting.
Cold, raised bead: increase current slightly or slow down enough to form a small puddle. Check that the tungsten is not contaminated and that you have a short arc. If the puddle refuses to wet the edges, recheck the surface for oil or oxide.
Blue, grey, or black weld area: improve shielding and reduce excess heat. A clean stainless TIG weld should generally be silver to light straw, though appearance varies with alloy and finish. Heavy discoloration signals oxidation and may reduce corrosion resistance. Let the weld cool under shielding when practical, and avoid repeatedly heating the same section.
Distortion: use more tacks, alternate weld direction, and allow cooling between short sections. Thin stainless expands and moves quickly. Clamping helps, but clamps cannot compensate for an overly long, hot pass.
What equipment is worth buying?
A basic DC TIG machine can do this work; AC output is not needed for stainless. A pedal is worthwhile for varied joints and heat-sensitive sheet, while a torch switch is cheaper and adequate for repeatable runs after testing. Choose a pure tungsten or an appropriate lanthanated tungsten and grind it lengthwise to a point. For thin sheet, a small-diameter lanthanated tungsten makes a fine arc possible, but it is fragile and easier to overheat than a thicker electrode.
Use a properly rated welding helmet, gloves, and protective clothing; TIG’s quiet arc still produces intense ultraviolet radiation. A TIG-capable auto-darkening helmet with low-amp sensitivity can help you see the start of a small puddle. A cheaper passive helmet is perfectly workable if it fits well and you can lower it reliably before striking the arc. Whichever setup you use, practise on matching scrap, make a short bead, and adjust current in small steps rather than chasing a perfect number.