TIG Welding

Safety

As MIG, plus: tungsten dust from grinding is best not breathed; thoriated tungsten is mildly radioactive — use lanthanated. HF start can upset pacemakers.

Done When

A uniform bead of overlapping crescents, silver or straw-coloured on stainless, with no discolouration beyond light gold — the colour is a thermometer.

Steps

Grind the tungsten to a point along its length, never across.

Clean the joint and the filler with acetone; aluminium with a dedicated stainless brush.

Set amps roughly one per thousandth of an inch of thickness; use the pedal to trim.

Strike, form a puddle, then dab filler into the leading edge — never into the arc.

Move, dab, move, dab: consistent rhythm makes the stacked-dime bead.

Ease off the pedal at the end and keep the gas on for post-flow so the hot metal is covered.

Tools

TIG machine with high-frequency start and AC for aluminium, 2 % lanthanated tungsten, pure argon, filler rods, foot pedal, gas lens, helmet, thin gloves.

The Science

Tungsten survives the arc because it melts at 3,400 °C. Argon shields the pool completely, so reactive metals like titanium and aluminium can be welded at all — aluminium needs AC, because the reverse half-cycle blasts off its oxide skin, which melts 1,500 °C hotter than the metal under it. Heat input is controlled independently of filler, which is what makes it precise.

How It Fails

Grey, sooty welds: gas coverage lost. A tungsten inclusion when the electrode touches the pool. Cracked aluminium from wrong filler or a rushed cool. Sugared stainless on the back from no back-purge.

Summary

The precise process: an arc from a non-consumable tungsten electrode under pure argon, filler fed by hand — for stainless, aluminium, titanium, and anything that has to look right.