Micro TIG Welding: A Practical Guide for Thin Metal

A 0.5 mm stainless steel filter housing arrives at the shop cracked along a seam. The MIG gun blows through it in a second, and a normal TIG setup with a 3/32 in tungsten puddles a crater right through the wall. What finally works is a small torch, a 0.020 in lanthanated tungsten, a few amps of current and a pulsed arc controlled by a foot pedal. That combination – tiny torch, tiny tungsten, tiny heat – is what welders mean by micro TIG welding, and it is the difference between repairing a delicate part and scrapping it.

What Micro TIG Welding Is (and What It Is Not)

Micro TIG welding is gas tungsten arc welding (GTAW) run at very low amperage, with a small torch, a fine tungsten electrode and, usually, a pulsed or spot-style arc. That is the whole idea: ordinary TIG scaled down for jobs where too much heat means a scrapped part. Everything later in this guide, from electrode choice to pulse settings, flows from it.

The naming confusion, untangled

The vocabulary here is genuinely messy, and the mess matters when you are ordering equipment or reading a spec sheet.

• GTAW is the official name. The American Welding Society lists gas tungsten arc welding among its defined processes, and it is the term you find in codes, procedures and qualification records.
• TIG is the trade abbreviation everyone says out loud. Not official, but universal.
• Heliarc is a marketing and shop-floor term used when helium rather than argon does the shielding. It describes the gas, not the process.
• Micro TIG, micro pulse welding, pulse arc welding and precision welding get used almost interchangeably by equipment makers and shops for the same family of low-current, high-control work.

Here is the honest catch: the AWS does not list micro welding as a separate, standardised process. There is no micro-TIG qualification category and no micro-TIG code clause. If a supplier tells you a machine is “AWS approved micro TIG,” treat that as marketing, not certification. What you are actually buying is a GTAW machine with a specific set of low-current capabilities.

How thin does “micro” actually mean?

The Edison Welding Institute frames its microjoining work around material thickness below roughly 0.5 mm, and technical literature often draws the line at a weld width under 0.5 mm or a heat-affected zone under 100 micrometres. Those are useful anchors, not a fence. Equipment makers routinely stretch the label across several millimetres, and plenty of real “micro” work happens on sheet that would never qualify as microjoining by a strict EWI definition.

General technical literature describes the micro-TIG process category as weld areas under about 18 square millimetres, with a current range of roughly 5 to 300 amps. That figure describes the process class, not the ceiling of one device. A bench-top unit might top out at 40 amps, and that is still micro welding. Amperage alone never settles the question, because arc stability and heat input depend on tungsten geometry, arc length, travel speed and shield gas as much as on the dial.

Micro TIG compared to the alternatives

Five process families cover the great majority of micro-joining work. Each wins in a different corner of the field.

Process	Where it wins	Where it struggles
Micro-TIG / pulsed arc	Thin sheet and tube, one-off parts, repairs, prototypes, tight access, any metal TIG handles	Slow cycle time, manual skill, not suited to tens of thousands of parts
Laser welding	Very thin material, high-volume automated runs, fine repeatability	Capital cost, Class 4 laser safety, reflective-surface restrictions
Micro resistance welding	Lowest cost per part, very fast cycles, electronics and battery tabs	Needs access from both sides, limited to specific joint designs
Electron beam welding	Deep, narrow, ultra-clean welds and very small parts	Requires a vacuum chamber, so batch rather than general job-shop work
Ultrasonic / wire bonding	Semiconductor chip connections and very fine wire to very fine pad	Niche to electronics; not a general fabrication answer

Choosing between them comes down to six questions: workpiece thickness, production quantity, material, access to the joint, budget and how much automation you need. One-off or repair work on a single part almost always favours micro TIG, because setting up a laser or a resistance welder for one component costs more time than the weld itself. High volume reverses the calculation entirely. Micro TIG also reaches places a laser head physically cannot, and it tolerates mixed materials and filler additions that a resistance welder cannot touch.

Where micro TIG is used every day

Look for it in medical devices such as catheters, guide wires, surgical instruments and hermetically sealed sensor housings. It is standard in electronics and sensors for battery tabs, thermocouples and fine wire connections where heat would damage the component. Jewellery, dental and model-making shops use pulsed micro TIG for settings, filigree and repairs near gemstones. In aerospace, thin-wall tubing, exhaust and instrumentation lines are a natural fit, and the process has its own set of standards and techniques covered in Aerospace TIG Welding: Standards, Techniques, and Training. Laboratory and prototype work relies on it for the same reason the rest of the trade does: a small torch, a small tungsten and a controlled arc can go anywhere a full-size torch cannot. For a sense of how a laser compares when volume climbs, see our guide to Alpha Laser Welding: Systems, Uses, and Safety Guide.

None of this makes micro TIG a rare speciality. It is a bench-scale skill with a wide reach, and the rest of this guide covers exactly how to set one up and run it well.

How the Micro TIG Arc Actually Works

Micro TIG isn’t its own process. It’s gas tungsten arc welding, or GTAW, simply run at much lower amperage with a smaller torch and a finer tungsten electrode. The physics remain identical to conventional TIG, only the scale is different. At its core, GTAW relies on three things: a non-consumable tungsten electrode with a melting point of about 3,422 degrees C (6,192 degrees F), an inert shielding gas (normally argon) to exclude air, and a constant-current power supply to keep amperage stable. This constant-current output is what gives TIG its precision, as small changes in arc length won’t cause large spikes in current. The basics of GTAW lay the groundwork for this level of control.

Striking the Arc and Keeping the Gap

Most micro TIG machines use a high-frequency start to ionise the gap between the tungsten and the workpiece without touching them. From there, the electrode should stay roughly 1.5 to 3 mm (0.06 to 0.12 in) above the metal. Keeping this gap short is critical, as a longer arc will wander, lose shielding, spread heat, and make travel much harder on walls as thin as 0.3 mm.

The heat comes from the arc column, the ionised gas between the tungsten and the molten pool. With no electrode contact, all of that energy is transferred through radiation and convection. The shielding gas both stabilises the column and keeps oxygen and nitrogen out of the weld.

Torch Position, Filler, and Crater Control

Torch angle is one of the quickest ways to shape your bead. Tilting the torch back roughly 10 to 15 degrees from vertical helps concentrate heat into a narrow finger at the front of the puddle rather than spreading it out. Moving in small circles or a tight weave keeps that tiny pool under control, with the leading edge of it being the target for filler.

Filler wire is always fed manually into the front of the pool, never directly into the arc. It must stay inside the gas shield, or it will oxidise and create a dirty, porous weld. At the end of the joint, the current must be ramped down through the foot pedal to slowly shrink the pool. Cutting power too abruptly is the most common cause of a centreline crater crack in micro work.

Pulse, Polarity, and Arc Stability

What truly makes a weld “micro” is the ability to limit heat input. Pulse welding achieves this by spiking to a peak current to melt a small amount of metal, then dropping to a lower base current to keep the arc alive without overheating. Between pulses, the part cools, narrowing the heat-affected zone and limiting distortion. On many precision parts, this allows for an autogenous weld with little to no filler at all.

Polarity also plays a large role in results. DCEN (electrode negative) puts most of the heat into the workpiece and is standard for steels, nickel alloys, and titanium. DCEP (electrode positive) puts more heat into the tungsten and is only used in select shallow cases. AC alternates between the two, with its electrode-positive half-cycle providing the oxide-scrubbing action needed to weld aluminium and magnesium. With the low currents used in micro TIG, factors like square wave output and high frequency are vital to prevent arc instability.

For reactive metals like aluminium, preparation is just as important as technique. The oxide layer must be removed before welding, and using the right aluminum cleaner for the job goes a long way towards preventing porosity without needing to rely on excessive heat to do the cleaning for you.

Choosing a Micro TIG Machine: Power Supply, Pulse Control and the Foot Pedal

Much of micro TIG is done on machines never sold as micro machines, and plenty of money goes on features nobody in the trade will ever use. What matters is narrower than the spec sheet: a power source that holds current steady, a torch small enough to reach the joint, and a way to feather amperage in real time.

What a GTAW power source has to do

Constant current is the non-negotiable requirement. In GTAW you hold the arc by hand, so arc length shifts whenever your hand trembles or the filler rod moves the torch. A constant current source pushes back and the amperage barely moves; a constant voltage source swings the heat, which on 0.3 mm sheet means burnthrough followed by a cold lump.

A micro TIG power source should also offer:

• DC output with fine resolution at the bottom of the range. On a 0.5 mm wall, 8 amps versus 11 amps is the difference between a clean bead and a hole.
• High frequency start, so the arc strikes without scratching the tungsten or marking a finished surface.
• Pulse and programme capability for repeat jobs and heat-sensitive material. Pulsing dumps heat in fast and lets the part cool between peaks, keeping the heat affected zone and distortion small on thin stainless and jewellery.

Why the foot pedal is close to essential

Welding 0.2 mm stainless is a conversation between your hand and the pedal. You creep current up until a pool forms, then roll back as the puddle travels so heat feeds the metal instead of dumping into one spot. Stop modulating and the pool grows, the wall thins, and you have a crater instead of a weld. Keep the pedal action smooth and linear; a detent or harsh spring makes fine work frustrating.

The two realistic purchase routes

	Dedicated micro or micro-pulse unit	Full-size pulsed TIG plus a fine torch kit
Output	Typically 60 to 150 amps, DC only	Wide range, AC available
Sold with	Slim torch, small gas lens, fine collets	You add a small torch, fine collets and gas lens
Best for	Jewellery, dental, electronics and lab work, always thin	Shops, maintenance departments and repair work
Limits	No 6 mm plate, no aluminium	Big machine alone will not do micro work

The honest trade-off: a bigger machine does not by itself make micro welds possible. What makes them possible is the torch and collets. A 3/32 in tungsten in a big torch neck on 0.5 mm sheet is still a furnace. Many of the best micro welds come out of ordinary machines fitted with a small torch and fine accessory kit.

Remote control, gas flow and grounding

Remote controls come as a foot pedal on a dedicated receptacle, a finger trigger on some torch handles, or a hand torch with a rocker switch. Check the amperage range the pedal actually controls: one that governs only the lower part of the range is no use for a thick job.

Gas flow deserves its own line. The regulator and flowmeter should deliver the low flows micro work needs, typically 4 to 8 litres per minute, and the torch should be designed so shield gas exits at the correct velocity. Overgassing a small torch can blow the pool sideways as much as undergassing lets the atmosphere in.

On the power side, OSHA requires that welding machines be grounded, that connections be checked before work starts, and that manufacturers’ instructions be followed strictly. The same standard caps open circuit voltage for manual arc welding at 80 volts AC and 100 volts DC, and OSHA 1910.252 sets the wider welding safety context, including cylinder handling and ventilation.

Single phase suits micro work; three phase only earns its place if you run a bigger shop machine hard for long periods. A dedicated, reliable ground is non-negotiable: sharing a socket with a grinder on a questionable ground is a good way to get a shock with your hand on the torch.

Cooling: air or water

Air-cooled torches are the norm for low-current work, used up to about 200 amps. Water-cooled torches become necessary up to about 600 amps, where heat conducted back into the torch body and cable insulation becomes a real problem. For micro TIG an air-cooled small torch is plenty, and coolant adds a pump, a reservoir and one more thing that can leak onto your bench.

The three purchases that matter

Strip away the feature list and three items do most of the work:

1. A micro TIG torch. Small body, small nozzle, able to reach tight spaces and hold a short arc. The limit is heat capacity: it is wonderful at 5 amps and will let go if you lean on it.
2. A foot pedal. The control that makes delicate welding possible. Look for smooth action and confirm it plugs into your machine’s pedal receptacle, which is not a universal standard.
3. A dedicated electrode grinder with a diamond wheel. A consistent point is worth more than a marginal machine upgrade, and a contaminated wheel ruins tungsten. The electrode and torch setup section of this guide covers that in more detail.

A gas lens, fine collets and a good regulator will quietly improve results more than a machine upgrade will.

What matters more than the machine

For code work the paperwork outranks the features: a welding procedure specification and a welder performance qualification decide whether your weld is acceptable, and pulse programmability does not substitute for them. AWS has authored more than 350 welding standards, developed by more than 200 technical committees and over 1,500 volunteers. Read the standard that governs your work, not the marketing sheet of the power source.

Training matters just as much. AWS education offers the CWI, CWS, CWE and CAWI professional programmes, certified welder paths and self-paced courses, and TWI’s technical FAQ library is a good free reference for the theory behind what you buy. A welder who understands heat flow can get good results from a modest machine; one who does not will burn thin parts on the best machine available.

If you also need aluminium, our guides to aluminium MIG welding and preparing aluminium correctly for welding cover the surface preparation and filler choices that micro TIG on aluminium depends on, since a dedicated micro unit without AC will not handle that metal at all.

Tungsten Electrodes, Collets and Torch Setup for Fine Work

Ask a new TIG welder what went wrong on their first thin-gauge job and you will hear: “The arc was all over the place and I kept breaking the tip.” Almost always the torch is at fault, not the machine. A tungsten of the wrong diameter, a collet with the wrong hole, a mismatched nozzle or a lopsided grind will scatter a low-current arc across the joint and wreck work that should have been routine.

How Tungsten Electrodes Are Classified

Tungsten specifications are standardised in ISO 6848 and AWS A5.12. The classification letter gives you the alloy and the colour code on the packaging; the number that follows gives the alloy content. Colours are a shop convention, not a guarantee, so read the label.

Designation	Material	Typical colour	Best used for
EWP	Pure tungsten	Green	AC welding of aluminium and magnesium
EWCe-2	2% ceriated	Orange/gray	DC work on steels and stainless, some AC
EWLa-1	1% lanthanated	Black	DCEN general work, good starting
EWLa-1.5	1.5% lanthanated	Gold	DCEN general work, good starting
EWLa-2	2% lanthanated	Blue	DCEN, improved current capacity
EWTh-1	1% thoriated	Yellow	DCEN general purpose, excellent stability
EWTh-2	2% thoriated	Red	DCEN general purpose, higher current capacity
EWZr-1	1% zirconiated	Brown	AC on aluminium, DC on alloys needing capacity

Standard sizes run from 0.5 mm (0.020 in) to 6.4 mm (0.25 in) in diameter, with lengths from 75 mm (3.0 in) to 610 mm (24.0 in). The micro TIG working family is 0.5 mm to 2.4 mm (0.020 in to 3/32 in), and for jewellery, electronics and thin sheet you will mostly live in the 0.5 to 1.0 mm range.

The Honest Trade-Offs

Thoriated electrodes give excellent arc start and stability and remain the classic general-purpose choice, which is why so many shops reach for them by reflex. The catch is that thorium is radioactive, so grinding dust and spent electrode disposal need care. Cerium and lanthanated electrodes give very good starting and stability with lower burn-off, and they are not radioactive. Zirconium raises current capacity and electrode life and is a good pick for aluminium.

For micro work on a bench where someone grinds electrodes all day, lanthanated is usually the sensible default: you give up very little in arc behaviour and take a radioactive-material headache off the bench.

Collets: The Part Most Shops Get Wrong

The collet is the small brass or copper sleeve inside the torch head that grips the tungsten and centres it in the gas stream. It holds the electrode, centres it so the arc does not wander, and conducts current into the torch.

Use a collet whose hole matches the electrode diameter exactly, and check that the hole is not worn or flared. A worn collet lets the electrode shift, the arc wanders off the work, and the weld goes somewhere you did not want it. A collet with a finer hole than the electrode will not hold it at all, so this is about a precise match rather than “tighter is better”.

Keep spare collets in every diameter you use and clean the collet body with a soft brass or nylon brush whenever you change electrodes. If you are fighting arc wander, suspect the collet before you blame the machine.

Nozzles, Gas Lenses and Diffusers

Choose the gas nozzle by its inside diameter relative to the electrode. The bore should be at least three times the electrode diameter, so a 1.0 mm electrode wants a 3 mm bore or larger and a 0.5 mm electrode wants a small 1.6 to 3 mm bore. Oversizing is fine on a micro job as long as you can still aim the shield, because gas coverage is what keeps the puddle clean.

Inside the nozzle, a gas lens is a fitted screen or spiral that narrows and directs the argon column, and a diffuser is a porous plug that smooths the flow. Both push shielding gas out of the torch and around the arc instead of letting it swirl. On delicate work with high shielding demands, such as hermetic sensor housings, a lens makes a real difference. Many small torches also accept an interchangeable cup so you can switch between a focused micro jet and a broader shield.

Grinding and Tip Shape

Grind on a dedicated electrode grinder with a diamond wheel, always longitudinally. Never grind across the electrode: that cuts a notch the arc latches onto, and the result is a wandering arc no amount of machine tweaking will fix. Take light passes and keep the tip shape consistent.

For DCEN work on steels and stainless, grind a sharp point, roughly 20 to 30 degrees included. For AC on aluminium, use a blunt or balled tip, because the electrode-positive half cycle scrubs the oxide and needs surface to work against. A sharp point on AC aluminium spits badly, which we cover in detail in our guide to prepping aluminium properly for welding.

A Quick Setup Checklist

• Electrode diameter matched to the current you will actually use
• New or cleaned collet of the exact matching hole size
• Tip ground to the shape the polarity and material demand
• Nozzle bore at least three times the electrode diameter
• Ground clamp clean and tight on the workpiece
• Argon flowing and covering the arc before you strike

Get these six right and most “my TIG torch will not behave” problems disappear. The basics of the gas tungsten arc process are worth revisiting alongside this setup work, because the hardware only makes sense once you understand what the arc needs from it.

Shielding Gas, Cleanliness and Fume Control

Micro TIG balances two invisible atmospheres. One is the gas you pour over the weld to keep oxygen and nitrogen away from a molten pool barely wider than a pinhead. The other is the air around your head, which the arc quietly fills with metal fume. Get the first wrong and the weld fails. Get the second wrong and you eventually become the statistic.

Argon, Helium and Blends: Choosing the Shielding Gas

Argon is the default GTAW shielding gas for one practical reason: it burns a stable arc that tolerates changes in arc length. On micro work, where the electrode may sit 1.5 mm from a 0.2 mm sheet, that forgiveness is everything. Move your hand a fraction and the arc keeps burning rather than snuffing out or wandering.

Helium is the alternative when you need more. It delivers deeper penetration and lets you travel faster, which suits high-heat-conductivity metals such as copper and aluminium, where heat sinks into the part before a pool can form. The trade-off: helium is harder to start and far more sensitive to arc length, so it punishes an unsteady hand. Argon-helium blends, commonly 75 percent helium or more, split the difference. Argon-hydrogen mixes boost heat on stainless but raise porosity risk, and small nitrogen additions are used in austenitic stainless and copper for metallurgical reasons.

On thin stock the blend matters less than the size and aim of the shield. A 0.2 mm sheet cannot afford a broad, lazy gas cloud. You want a small nozzle held close, with just enough flow to cover the pool, because excess flow creates turbulence that sucks air into the arc. A drafty bench ruins the arrangement: an open bay door, a fan, even a nearby grinder will blow the shield aside and leave a grey, porous weld.

Cleanliness: The Biggest Lever You Control

Cleanliness is the single biggest controllable factor in weld quality, and micro work is unforgiving about it. Every contaminant left on the surface becomes a defect at ten times the scale of a normal weld, because the pool is so small.

• Steels and stainless: wipe with alcohol or acetone before welding. Grease, oil, paint and marker ink break down into gas in the arc.
• Aluminium: remove the oxide mechanically with a dedicated stainless wire brush, or use a chemical prep. The oxide melts at far higher temperatures than the aluminium beneath it.
• After grit blasting: follow with a brush. Blasting drives grit into the surface, and embedded particles turn into inclusions.

Beginners miss one thing here. DCEN, the polarity used for steels, nickel and titanium, gives you no cleaning action at all. It is a one-way heat pump, so all oxide removal must happen before the arc starts. Our guide to the right aluminum cleaner for welding walks through the solvents, brushes and sequence for preparing aluminium in detail.

The Air You Breathe: Fume, Ventilation and the Rules

Now the part that rarely makes it into torch-setting videos. Welding fumes are a complex mixture of metal oxides and gases, and the manganese in them is a well-documented neurological concern. The NIOSH welding topic page is blunt about it, and the NIOSH Pocket Guide entry for welding fumes lists them as a potential occupational carcinogen, with lung cancer as the cancer site.

The manganese exposure limits are worth knowing, and welding inside a confined space significantly increases exposure, because the fume has nowhere to go and you are sitting in it:

Authority	Manganese limit	Type
NIOSH REL	1 mg/m³	TWA
NIOSH STEL	3 mg/m³	Short-term
OSHA PEL	5 mg/m³	Ceiling
ACGIH	Separate TLVs	Respirable & inhalable fractions

Ventilation is not optional, and OSHA 1910.252 sets the thresholds. Mechanical ventilation is required when you weld in a space under 10,000 cubic feet per welder, in a room with a ceiling under 16 ft, in a confined space, or where partitions block cross ventilation. Minimum airflow is 2,000 cubic feet per minute per welder. The local exhaust hood table scales with distance from the arc: 150 cfm through a 3 inch duct held 4-6 inches from the arc, rising to 600 cfm through a 5.5 inch duct at 10-12 inches. The closer the hood, the less air you move.

For a broader look at shop safety across processes, our carbon arc gouging and air arc safety guide covers the same principles applied to a much hotter, dirtier process.

The Takeaway

Good extraction, good shielding, clean metal. Pull the fume away from your face before it reaches your breathing zone, keep a tight gas shield over a pool you can barely see, and never let a contaminant into the arc. Do that consistently and micro TIG becomes a skill you control rather than a fight with the process.

Materials and Joints: Stainless, Aluminium, Copper, Titanium and Nickel Alloys

A micro TIG job is decided long before you strike an arc. The same torch, the same 20 amps and the same foot pedal can produce a beautiful hermetic seal in stainless and a puddle in aluminium. What changes from metal to metal is the combination of polarity, gas, electrode and surface preparation, and on thin work that combination matters more than any machine feature.

One reason GTAW holds its own on delicate assemblies is that filler metal is added by hand rather than transferred across the arc. The weld metal therefore stays chemically very close to the base metal, which is why TIG is the process of choice for critical corrosion-resistant and sealing operations (TIG process overview).

Stainless and carbon steel

Start with DCEN, a thoriated or lanthanated electrode tapered to a sharp point, and pure argon for thin work. Helium gets added as the joint thickness and travel demand grow, mainly to raise penetration and travel speed.

Preheat decisions follow the metallurgical family. Austenitic stainless steels generally need no preheating. Martensitic and ferritic stainless steels and tool steels may require preheat to slow the cooling rate, which prevents hard martensite forming in the heat-affected zone and cracking it. Mild steel under roughly one inch thick usually needs no preheat either. On micro parts the goal is to put the heat in and get it out, because the smaller the HAZ, the less the part moves.

Aluminium and magnesium

Aluminium is welded with AC so the electrode-positive half cycle scrubs the oxide film off the puddle. DCEN with helium is an alternative for automated work where a machine manages the cleaning action. For AC work, pure or zirconiated tungsten is preferred over thoriated, because thoriated electrodes are more likely to spit particles into the weld, and blunt tips are preferred over sharp points.

Heat input makes or breaks an aluminium weld. Aluminium may be preheated to 175-200 degrees C (347-392 degrees F) and thick magnesium to a maximum of 150 degrees C (302 degrees F) to improve penetration and travel speed. DCEP with a thoriated tungsten electrode and pure argon is used primarily for shallow welds, especially where joint thickness is under 1.6 mm (0.063 in). Surface prep cannot be skipped either. Our guide to aluminum cleaner for welding covers the degrease-and-brush routine that keeps oxides out of the puddle.

Copper and copper alloys

Copper throws heat away faster than almost anything else you will meet, so it demands helium and a higher heat input than the thickness suggests. The result is a wider, deeper pool that behaves nothing like a stainless puddle. Pulse control and filler timing become critical: the pool grows fast, the filler can melt before it reaches the front edge, and the bead wanders. Autogenous welding is often cleaner than fighting a runaway pool.

Titanium and nickel alloys

Both run DCEN with argon, and both punish carelessness. Titanium needs scrupulous cleaning, high purity gas and an absolute ban on copper or brass contamination. Copper contamination is a well-known cause of titanium weld porosity, and it is transferred by touch, by shared tools, by brass fittings on the torch. Nickel alloys, including the precipitation-hardened families, need clean filler, controlled heat and inert handling. If you work in these areas regularly, a shop reference such as aerospace TIG welding standards and techniques is worth reading alongside the practical routine, and Alloy 20 welding procedures covers a corrosion-resistant nickel-iron-chromium alloy in detail.

Dissimilar metals

Welding stainless to carbon steel or to nickel alloys means choosing a filler that satisfies both sides, and that choice drives the whole procedure. Two standard routes exist: buttering, where the less corrosion-resistant or less weldable metal is overlaid with a compatible filler before the joint is made, and cladding, where a corrosion-resistant layer is placed over the base and the weld is made through it. Both add a step and both buy you a joint that would otherwise fail from galvanic or dilution effects.

Joint geometry and fit-up

On thin stock, edge preparation and fit-up decide the weld before the torch does. The four geometries you will meet most are butt, lap, corner and tube-to-tube. The open-lap joint, where the two sheets overlap without a groove, is quick and forgiving but leaves you with an unreadable root and two surfaces to clean. For exhaust and instrumentation tubing, a two-pass micro TIG weld, a root pass followed by a cap pass, is the usual answer because it gives a sound sealable root and a clean visible surface.

Metal	Polarity	Gas	Electrode tip
Stainless, carbon steel	DCEN	Argon, helium as thickness grows	Pointed, thoriated or lanthanated
Aluminium, magnesium	AC (EP half cycle)	Argon	Blunt, pure or zirconiated
Copper, copper alloys	DCEN	Helium	Pointed, lanthanated
Titanium	DCEN	High purity argon	Pointed, lanthanated
Nickel alloys	DCEN	Argon	Pointed, lanthanated or thoriated

Setting Parameters: Current, Pulse, Filler, Travel Speed and Heat Input

No settings list transfers between jobs. Any list you are handed is a snapshot of someone else’s machine, gas and joint. Start from a known reference point, run a test coupon, and adjust by eye and by feel until the bead fuses properly.

Current and thickness

A common shop rule of thumb for thin stainless on DCEN is roughly 1 amp of current per 0.001 inch of thickness, so a 0.5 mm (0.020 in) housing starts near 20 amps before adjustment. Aluminium and copper pull heat away quickly and need more current at the same thickness, while stainless runs cool. A wider gap or poor fit-up raises the current needed to fuse the root, and a backing bar or heat sink lets you run cooler.

Both errors are easy to recognise. Too little heat input limits penetration, so the bead sits on the surface with cold, un-fused edges. Too much widens the bead and raises burn-through and spatter risk. On micro work the failures still matter: an un-fused bead leaks, and one that melted through will not hold pressure.

Electrode diameter is the other half of the calculation. These are typical DCEN starting ranges, not rules:

Tungsten diameter	Typical current range (DCEN)
0.5 mm (0.020 in)	5 to 20 A
1.0 mm (0.040 in)	15 to 80 A
1.6 mm (1/16 in)	70 to 150 A
2.4 mm (3/32 in)	150 to 250 A

Check the electrode supplier’s published data before committing, since tip geometry and alloy change the numbers. For micro TIG you will usually be between 0.5 mm and 1.0 mm; fine-scale joining practice is covered in Lampert’s micro welding guidance and EWI’s microjoining resources.

Pulse parameters

Pulsing is what separates micro TIG from ordinary thin-sheet TIG, and each control does something different.

• Peak current dumps heat into the pool quickly, in a burst.
• Base current maintains the arc between bursts, just enough to keep the pool alive.
• Frequency, from tens to several hundred hertz, sets how often those cycles happen.
• Pulse duration (on-time) decides how much heat lands in the work during each burst.
• Upslope and downslope soften the start and taper the end of the weld.

In micro work the peak-to-base ratio is usually modest, around 1.5:1 up to 3:1, because a big peak on a 0.3 mm wall is a burn-through. Many machines tie pulse duration to frequency through a sync control, so independent control is worth paying for. Very high frequency can strip the arc of its cushion and make it wander, so a moderate frequency with a well-shaped pulse usually beats the highest setting available.

Filler metal and technique

Use fine filler, typically 0.5 mm to 1.0 mm, matched to the parent metal. Feed it into the leading edge of the pool, not behind the arc, and keep the wire inside the gas shield so it does not oxidise. With aluminium, hold the filler back from the arc so it does not melt early and coat itself with oxide; the practical guide to aluminium MIG welding covers the handling habits that carry over. For code work, filler must meet the governing code specification, as noted in OSHA’s general welding requirements.

Travel speed and heat input

Travel speed is the counterweight to current. Too slow and the weld runs cold, with a narrow, sluggish bead that has not properly fused. Too fast and you burn through before the pool can spread. On very thin material speed is your best burn-through control.

Heat input puts a number on it. The standard relationship, as described in the reference material on tungsten inert gas welding, is:

Heat input (kJ/in) = (amperage × arc voltage × 60) ÷ (travel speed in inches per minute × 1,000)

Drop the 1,000 and you get joules per inch. A 25 amp weld on 0.5 mm stainless at 10 volts of arc and 50 inches per minute gives (25 × 10 × 60) ÷ (50 × 1,000) = 0.30 kJ/in. At 20 ipm with the same amperage, nearly double the heat goes into the part.

Two cautions. Arc voltage is not fixed; it drifts with arc length, shielding gas and electrode condition, so treat the result as an estimate. And heat input alone does not describe a good weld on thin material, where fusion and dwell matter more. The formula guides you; it does not qualify the procedure.

Qualification is what actually counts

For code work the settings above are inputs, not permission: you need a welding procedure specification and a welder performance qualification. AWS D1.1/D1.1M:2025-AMD1 covers structural steel, AWS D1.2/D1.2M:2026 covers structural aluminium, AWS D1.6 handles stainless steel, and ASME Section IX governs ASME B31 work. Thin-wall aerospace work has its own demands, see our guide to aerospace TIG welding standards and training.

AWS education offers in-person, online instructor-led and self-paced paths (Certified Welder, Inspector, Supervisor, Educator), and TWI’s technical knowledge library publishes free FAQs and best practice guides. Keep a log of your settings and why.

Common Micro TIG Mistakes and How to Diagnose Them

Micro TIG fails quietly. The arc still strikes, the machine still beeps, and you still get a bead that looks like a bead. But the joint is porous, or the tungsten is now part of the part, or that “seam” is really a hole with a shiny edge. Troubleshooting works best when you stop guessing and start reading the defect, because each one has a signature cause that narrows the search fast.

Porosity: the signature GTAW defect

Porosity shows up as gas bubbles, open pits or a spongy, cratered bead. It is the number one problem in gas tungsten arc welding and it is almost always a shielding failure. On DCEN the power supply gives you no cleaning action, so oxide removal before welding is entirely your job. Whatever you skip on the joint will show up in the weld.

The usual causes, roughly in order of how often they turn up:

• Low or mis-aimed gas flow. The nozzle is not centred on the joint, so the tungsten and pool sit outside the protective column of argon. Check flow at the nozzle with a flowmeter, not just at the regulator.
• Drafts and open doors. A shop door opening on the far side of the bench will strip the shield off the arc. A windshield of heavy sheet, or even a cardboard screen, solves it.
• Contamination. Oil, grease, paint, moisture, cutting fluid and loose oxide all generate gas or float to the surface. Degrease and brush the joint right before welding.
• Old or contaminated gas. A cylinder left open, or a bottle with water in it, will not shield properly.
• Torch held too far away. Every extra millimetre of arc length weakens the shielding and widens the heat pattern. Micro work wants a very short arc.

The fix is boring and effective: clean joint, verified argon flow, wind break, tight arc. For a specific example of how much joint preparation matters on sensitive alloys, see our guide to prepping aluminium properly for welding.

Tungsten contamination and inclusions

A dark, flickering arc with a wandering puddle and a bead containing small bright specks points to tungsten in the weld. When the arc wanders, the welder reflexively dips the electrode into the pool, which melts a bit of tungsten. Those droplets get carried into the puddle and end up in the finished joint.

Common triggers:

• Dipping the electrode into the pool, the single most common cause
• Letting the filler wire touch the tungsten
• A dirty or oversized collet that lets the electrode wobble
• An electrode too small for the current, so the tip overheats and sheds particles
• Weak gas coverage at the tip, letting the hot tungsten oxidise and sputter

Exceeding the current capability of the electrode can result in tungsten inclusions in the weld, and radiography is how you find them. Prevention is straightforward: switch the electrode type to something rated for the amperage, or step up to a larger electrode diameter.

Spitting on aluminium

Aluminium makes spitting far more likely than steel, and a spitting bead looks like a caterpillar trail of small blobs. The root cause is usually a spit-prone electrode combined with the wrong tip geometry. Pure tungsten or a zirconiated electrode with a blunt tip is the safer choice for aluminium, since a sharp, thin, overheated point tends to shed metal. Keep amperage modest, keep the arc short, and expect some cleanup of the bead before it looks presentable.

Arc wander and an unstable arc

If the arc chases around the joint, the sound changes pitch, or the arc refuses to strike cleanly, work through this list in order:

• A dirty or badly ground tungsten, with the tip wandering off the centre of the electrode
• A loose, wrong-size or contaminated collet, which lets the electrode shift inside the cup
• Incorrect polarity, which flips the heat distribution
• A worn cable connection at the work clamp or the torch, a common and often overlooked cause
• Low gas flow starving the arc
• Rectification on AC, where the arc can wander if the machine’s balance is poor

OSHA requires that cables with splices within 10 feet (3 m) of the holder not be used, and that coiled welding cable be spread out before use to prevent overheating and insulation damage, so check your leads as part of the diagnosis, not just the torch. Full detail on cable and lead requirements is in OSHA 1910.252.

Burn-through and crater holes

On a 0.3 mm wall, burn-through is the welder’s own heat arriving faster than the metal can spread it. Causes are too much current, no filler, too fast a travel speed, or too little backing under the joint. The fixes are direct: feather the pedal and drop the amperage, feed filler to fill the gap, slow down slightly, and put a copper backing bar under the work to soak up heat and pull the puddle back together. A smaller, more deliberate pool fixes what a bigger machine cannot.

Lack of fusion and cold, narrow beads

A bead that looks like a neat little rope but peels off the plate, or one that sits proud and dark with no melting into the base metal, is a fusion problem. The heat was not there, or it was not delivered where it mattered. Typical causes are too little current, travel so slow the arc just treads rather than melts, dirty or oxidised metal, a torch at the wrong angle, or an oversized electrode drawing heat away from the work. Fixes: raise current a small step, check the grind, clean the metal, and hold the torch at a 10 to 15 degree tilt from vertical with the arc directed into the joint.

Excessive spatter and a wide, flat bead

A wide, flat, splattered bead means too much current for the joint, a long arc, an arc length that keeps changing, or a hot electrode working well past its capacity. All four push more heat into the pool than the bead can absorb. Reduce amperage, shorten the arc, let the electrode cool between welds, and confirm the electrode diameter suits the amperage you are actually running.

Symptom	Most likely cause	First adjustment
Porous, pitted bead	Low or mis-aimed gas flow, draft, dirty joint	Verify argon flow at the nozzle, add a wind break, degrease the joint
Tungsten specks in the weld, wandering arc	Electrode dipped in the pool, filler touching the tungsten	Grind the tip on the diamond wheel and do not reuse it
Arc refuses to strike or runs off to one side	Dirty or uneven grind, loose or wrong collet	Regrind to a consistent point and reseat the collet
Spitting on aluminium	Spit-prone electrode, sharp tip, high amperage	Switch to pure or zirconiated tungsten with a blunt tip, lower the current
Hole blown through the joint	Too much current, no filler, no backing bar	Feather the pedal down, add filler and a copper backing bar
Cold, narrow bead that will not fuse	Too little heat, too slow travel, dirty metal	Raise current one step, clean the joint, tilt the torch 10 to 15 degrees
Wide, flat, spattered bead	Excess amperage, long or wandering arc, overheated electrode	Shorten the arc and step the amperage down
Crack beside an otherwise good bead	Rapid cooling, wide HAZ	Add a backing bar or chill block, narrow the bead, slow the cooling

One habit ties all of these together: change one variable at a time. If you drop the current, change the gas flow and swap the electrode within the same five minutes, you have learned nothing about which fix actually worked, and the next weld on the real job will be a guess.

Where Micro TIG Earns Its Keep: Real Jobs and Process Comparisons

Understanding how a pulsed arc behaves only gets you so far. The decision that actually matters on a shop floor is when a micro TIG set is the right answer, and when it is an expensive way to do something a laser, a resistance welder or a wire bonder does better.

Medical technology and hermetic sealing

Medicine is the traditional home of micro joining. Catheters, guide wires, surgical instruments and implant housings all contain joints thinner than a human hair, with tolerances tighter than conventional welding can hold. The most demanding version is hermetic sealing: closing a sensor, capsule or implant housing so that nothing crosses the weld. A leak measured in parts per billion is enough to ruin a pressure sensor or let fluid into an implantable capsule, so the weld is not merely structural, it is a performance specification. Validation is typically done by helium leak test, which is why hermetic sealing stays one of the core micro TIG applications rather than a niche extra.

The Edison Welding Institute microjoining program lists micro TIG among its core technologies and has applied it to smoothing wire ends on an ear, nose and throat surgical device, alongside lighting, sensors, miniature motors and fibre optics assemblies. EWI labs run micro-TIG welders as part of that work.

Electronics, sensors and fine wire

Battery tabs, thermocouple junctions, sensor housings and fine wire connections share one problem: the wire is trivial to weld, but the component behind it is not heat tolerant. A weld that would be fine on a steel bracket can anneal a magnet, crack a ceramic substrate or damage a sensor die. A pulsed micro TIG gives a small, fast, controlled pool, which is why electronics work is the most common reason a technician buys a dedicated micro unit. The Lampert micro welding overview shows how the same pulsed arc scales across these small assemblies.

Jewellery, dental and model making

Jewellery is where micro TIG became a household name. Settings, chain links, filigree and nickel silver frames are joined with spot or seam welds on the bench. A pulsed, spot-capable machine is ideal near gemstones and finished work because the current can be dumped and then reduced, keeping the heat in the joint instead of driving it into the stone setting or the polish. The same logic applies to dental and model-making work, where a single bad bead means remaking the piece.

Aerospace and thin-wall fabrication

Thin-wall tubing, exhaust components and instrumentation lines are micro TIG territory because the wall thickness leaves no room for error in heat input. Aerospace TIG welding standards and techniques are covered in more detail elsewhere, but one research finding is useful here: published work on micro TIG tube welding of 0.2 mm AISI 321 austenitic stainless steel found that weld seam width and heat-affected zone were governed by the welding power parameters. On very thin wall you do not chase settings, you control the parameters and the geometry follows.

Repair and maintenance

Most shops meet micro TIG first as a repair tool rather than a production process. Cracked filter housings, worn tool edges, chipped turbine tips, split brackets and broken sensor bodies are all jobs where scrapping the part costs far more than the welder. A dedicated micro unit pays for itself quickly here, because it can be set up on a bench in minutes and used on the spot instead of routing the part out.

How micro TIG compares with the alternatives

Process	Typical range	Where it wins	Main limitation
Micro TIG / pulsed arc	About 0.1 mm upward	One-off parts, repairs, precious metals, single-sided access	Manual, slower cycle time
Laser micro welding	Below roughly 0.1 mm	High-volume automated runs, tiny deep seams	Class 4 laser safety and high capital cost
Micro resistance welding	Sheet, wire, foil	Cheapest and fastest in high volume	Needs access from both sides
Electron beam	Micron scale	Ultimate precision, very narrow deep welds	Requires a vacuum chamber
Ultrasonic / wire bonding	Wire to pad or chip	Standard for semiconductor chip connections	A different joint type entirely

The honest comparison is not about which process is best, it is about which one fits the job. Laser micro welding is the stronger option below roughly 0.1 mm and for high-volume production, but it drags in Class 4 laser safety controls and a much larger capital outlay. Micro resistance welding is cheapest and fastest in volume, at the price of needing electrode access on both sides of the joint. Electron beam gives unmatched precision, but the vacuum chamber is a barrier most shops never clear. Ultrasonic and wire bonding own the semiconductor field, where wire bonding remains the standard method of connecting to chip pads.

Micro TIG and pulsed arc welding remain the pragmatic first choice from about 0.1 mm upward, for single pieces, repairs, prototypes, precious metals and joints you can only reach from one side. That is why a compact micro set with a small torch and a foot pedal earns a permanent place in the shop. The Alpha laser welding guide is worth reading if you are weighing a laser purchase against it.

Building a Micro TIG Setup, a Practice Plan and a Quality System

The Bench Setup

• A stable bench. You cannot hold a 5 mm puddle steady on a flimsy table.
• A real ground clamp on bare metal. Poor grounding causes erratic arc behaviour at micro currents.
• An argon regulator and flowmeter sized to your cylinder. Check flow with a cold cup, then set it for your nozzle size.
• A foot or finger control, the heat valve. The welding equipment buying guide shows how to judge a machine.
• A small torch with a ceramic nozzle and the right collets. Spare collets in every diameter, plus a gas lens for delicate work.
• A dedicated diamond-wheel electrode grinder and a sealed storage tube. A bench grinder contaminates the wheel and ruins your tips; tungsten picks up moisture and dust.
• Filler metal matched to the job, small diameters, stored dry. The electrode selection guide covers matching filler to base metal.
• A backing bar or copper heat sink. On thin work this is the difference between a good weld and a hole.
• Fume extraction and eye protection, a helmet or hand shield with the correct shade lens plus local exhaust. The gas welding safety walkthrough covers the fume side.

Safety That Is Not Optional

OSHA’s filter lens guide calls for shade 11 for gas-shielded arc welding on nonferrous metals and shade 12 on ferrous metals. Arc light and UV still reach skin and eyes nearby, so keep spectators and reflections away.

Fire watch is not optional. OSHA requires a fire watch wherever appreciable combustible material sits within 35 feet of the work, maintained for at least half an hour after welding stops. Hollow containers must be vented and cleaned of flammable material, with inert gas purging recommended. If you pause for long periods, remove electrodes from their holders and disconnect the machine. Handle cylinders upright and chained, valve closed, capped when not in use.

A Staged Practice Plan

Stage	Material	Focus
1	Mild steel scrap	Torch and puddle control, foot pedal feathering
2	Stainless sheet	Heat control, colour, crater fill
3	Aluminium	AC cleaning cycle, surface prep
4	Copper	Helium, higher heat input, filler timing
5	Your actual part	Test coupon first, then the real job

Never skip stage five’s coupon: weld a scrap of the same material and thickness first and you learn what the part will do before you damage it. Work the stages in order and confidence comes in weeks, not years.

A Simple Quality System

Keep a weld log in a notebook: material, thickness, machine, amperage, gas and flow, electrode size and type, filler, pulse program, and the result, good or bad. Inspect visually every time, add dye penetrant on critical stainless work, and leak or pressure test where the joint must be hermetic. For code work, the route is a welding procedure specification plus welder performance qualification, drawn from the AWS standards library and ASME Section IX.

The Learning Path, and the Takeaway

AWS offers training in in-person, online instructor-led, self-paced and dual formats, all aligned to its certifications and standards, so a route fits your schedule. TWI’s technical FAQ and job knowledge material is excellent free background reading. Then get back to the bench.

Micro TIG is learnable, and most of the learning happens in the first twenty hours of puddle control. A small torch, fine tungsten, steady hand and a patient foot pedal beat expensive equipment every time. Keep the arc short, the pool small, the metal clean and the gas flowing, and treat every weld as information. That is how beginners become the people others send their delicate work to.

Frequently Asked Questions

What is the difference between micro TIG welding and regular TIG welding?

It is the same process – gas tungsten arc welding – run at much lower amperage with a smaller torch, finer tungsten and very tight heat control. Regular TIG is normally thought of as structural or sheet work; micro TIG is aimed at thin, delicate or heat-sensitive parts where the heat-affected zone and distortion must be kept tiny.

What is the thinnest material micro TIG can weld?

Around 0.1 mm (0.004 in) is the practical lower limit for pulsed micro-TIG in industrial use, with weld spot sizes of roughly 0.2 mm and up. Below that, laser welding, micro resistance welding or ultrasonic/wire bonding usually take over.

Do I need a special machine for micro TIG, or can I use a normal TIG welder?

A normal TIG welder with DC, high-frequency start and a foot pedal can do fine work if you add a small torch, fine collets and a gas lens. A dedicated micro or micro-pulse unit gives you finer current control, repeatability and better shielding, which matters for production and jewellery or electronics work.

Which tungsten electrode is best for micro TIG?

Lanthanated (EWLa-1.5 or EWLa-2) and ceriated (EWCe-2) electrodes are the usual choice because they start easily, run stably at low current and are not radioactive. Thoriated (EWTh-2) electrodes still perform excellently but thorium is radioactive, so dust and disposal need care.

Can you micro TIG aluminium?

Yes, but it is the hardest material in the micro family. Alternating current with its electrode-positive cleaning half-cycle, a blunt pure or zirconiated tungsten, clean oxide-free surfaces and a preheat of 175-200 degrees C are the standard countermeasures. Some industrial micro units include a dedicated aluminium mode.

What causes pinholes in a micro TIG weld?

Almost always shielding or cleanliness: gas flow too low, a torch held too far from the work, a draught in the shop, or oil, paint, moisture or oxide left on the joint. On DCEN the arc does not clean the metal for you, so the joint has to be prepared properly before you strike.

Is micro TIG welding safer than other processes?

It is not inherently safer. TIG produces no smoke of its own but the arc light is very bright, generating intense UV plus ozone and nitrogen oxides, and the fumes from the base metal are still present. You still need proper eye protection, extraction, fire control and clean handling of the workpiece.

When is micro TIG the wrong process to use?

It is the wrong choice for high-volume, high-cycle-time production where laser or resistance welding wins on economics, for material below about 0.1 mm, and for chip-level connections where wire bonding is the standard. It is also poor value if you need high amperage and thick-section capability more than precision.

Do I need to qualify a micro TIG procedure?

For repair and hobby work, no. For code-governed fabrication of pressure parts, structural aluminium or stainless, yes – you need a qualified welding procedure specification and a welder performance qualification, typically to AWS D1.1, D1.2 or D1.6, or ASME Section IX.

How do I stop burn-through when welding very thin sheet?

Lower the current and let the foot pedal do the work – feathering the current as the pool grows is the single most effective technique. Add filler metal, travel slightly faster, use a backing bar or heat sink under the joint, and keep the arc short and the puddle as small as the part allows.