Tig welders explained: AC, DC, and what the extras are for
What a tig welder is, why aluminum needs AC, what high frequency start, lift tig and a foot pedal do, and the specs to check before buying.
Tig is the process people picture when they think of neat, stacked welds on a bike frame or a stainless exhaust. It is precise and clean. It is also slow, and the machines vary more than any other kind, so the listing needs careful reading.
Two questions sort tig machines. Does it output AC as well as DC, which decides whether it can weld aluminum? And how does it start the arc, by touch or by high frequency? After that, check rated output, duty cycle and input current, as with any welder.
Torch, filler and pedal
The torch holds a tungsten electrode, a hard metal rod ground to a point that carries the arc (the electrical discharge that melts the metal) without melting itself. Argon flows around it to shield the puddle. You melt a small pool on the joint and dab filler rod into its leading edge with your other hand. A foot pedal or a thumb control varies the current as you go. How that compares with the other processes is in mig vs tig vs stick.
Everything must be clean: the metal, the filler and the tungsten. If the tungsten touches the puddle, you stop and regrind it.
The features, decoded
| On the listing | What it means |
|---|---|
| DC tig | Steel, stainless, chromoly, copper. Not aluminum |
| AC/DC tig | Adds aluminum and magnesium |
| Lift tig | Touch the tungsten to the work and lift to start. No pedal needed, fewer parts |
| HF start | The arc starts without contact. Cleaner, and standard on dedicated tig machines |
| Foot pedal or torch amperage control | Lets you vary heat mid-weld. Often sold separately |
| Pulse | Switches between high and low current many times a second to limit heat on thin metal |
| AC balance, AC frequency | Aluminum settings: how much cleaning action, and how focused the arc is |
| Gas solenoid, pre-flow and post-flow | The machine starts and stops the argon. Without one, you open a valve on the torch by hand |
What else a tig setup needs
- A cylinder of pure argon and a regulator or flowmeter. This is not the argon and carbon dioxide mix used for mig, so a shop that does both keeps two cylinders.
- Tungsten electrodes in the right diameter, and a way to grind them. A separate guide on tungsten types is planned.
- Filler rod matched to the base metal.
- A torch, if the machine does not ship with one. Air-cooled torches suit home use. High current for long periods needs a water-cooled torch and a cooler.
- Gloves thin enough to feel the filler rod, and full coverage for your skin. Tig makes little smoke, so nothing dims the arc, and the ultraviolet is intense. The tig rows in the helmet shade chart suggest darker shades than the minimum for that reason. A helmet rated for low amperage tig matters too, because a small arc can fail to trigger weaker sensors. Our helmet roundup lists each pick’s lowest tig rating.
Power and duty cycle
Tig welds are often long and continuous, so duty cycle matters more than it does for short mig tacks. Read the rated output for the tig process specifically. On multiprocess machines it can differ from the mig rating. The ARCCAPTAIN MIG205MP, for one, publishes tig and stick ratings on its nameplate and no mig rating at all. Input current and breaker figures for the machines we have checked are in the welder comparison table.
Tig usually draws less from the wall than stick or mig at the same output current, because the arc voltage is lower. The YesWelder MCT-520 manual lists a 29 amp maximum input for tig on 110 volts, against 37 for mig and 45 for stick. That is still beyond a household circuit at full output. See welder amp draw.
Routes into tig
If you want tig alongside mig and stick on steel, a multiprocess machine with DC tig is the low-cost route, and our multiprocess roundup notes which picks have high frequency start. If aluminum is the goal, look for a dedicated AC/DC tig machine. We compare two budget ones in PrimeWeld TIG225X vs ARCCAPTAIN TIG200P.
Tig’s precision is why it is used on critical work such as pressure piping and aircraft parts. That work is done by certified welders to written procedures. Nothing on this site says a weld will hold a load or pressure.
Frequently asked questions
What is a tig welder?
A welder that strikes the arc from a tungsten electrode that does not melt. You hold the torch in one hand and feed filler rod with the other, and shielding gas, normally pure argon, flows from the torch. The formal name is gas tungsten arc welding, GTAW.
Do I need AC to tig weld aluminum?
Yes, in practice. Aluminum carries a tough oxide skin that melts at a far higher temperature than the metal under it. Alternating current breaks that skin up on one half of each cycle and welds on the other. A DC only tig machine suits steel, stainless and chromoly, and is not the tool for aluminum.
What is the difference between lift tig and high frequency start?
They are two ways of starting the arc. With lift tig you touch the tungsten to the work and lift away. It is simple, and can leave a trace of tungsten in the weld. High frequency start jumps the arc across a small gap without contact, which keeps the tungsten and the weld cleaner. HF start usually comes with a gas solenoid and a pedal connection.
Can a multiprocess welder do real tig?
Most offer DC tig, which covers steel and stainless. Many are lift start only, and some sell the torch separately. A few budget machines add high frequency start. Very few multiprocess machines offer AC, so aluminum tig generally means a dedicated AC/DC machine. Check each of these on the listing.