What Tungsten electrode Diameter do
I use?

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Is there a rule of thumb on what diameter tungsten to use?

Some textbooks and technical guides recommend using the smallest tungsten electrode possible for best results .

But is that very practical?

Does it even hold true with todays TIG inverters?

Lets look at it from a practical standpoint.

Tungsten electrodes are kind of like stick welding electrodes in that they have a recommended amperage range....and if you get outside that range, things get wonky.

If you use a large diameter tungsten on a very low amperage job, you may or may not get a crisp arc start or a stable arc at low amperage.

(Think 1/8" electrode on razor blades)

On the other hand if you try to weld thick metal at 200 amps using a small 1/6" tungsten, the tip will melt away and most likely dump into your weld.

Another consideration is that different types of tungsten electrodes can vary greatly on maximum amperage capability.

Pure Tungsten

Pure tungsten was recommended for years for aluminum because of its ability to hold a nice balled tip on AC.

But pure tungsten has the lowest amp capacity of all the tungsten electrodes.

That’s why it balls up so easily on the tip and why it has been used for years to weld aluminum on older transformer machines.

Zirconiated will hold up quite a bit better than pure tungsten for AC TIG welding of aluminum and is a pretty good choice for transformer machines because it balls nicely but handles more amperage than pure tungsten electrodes.

Pretty much all of the other types of tungsten electrodes rated for both AC and DC  have similar recommended amperage ranges.

2% thoriated, 2% lanthanated, 2% Ceriated, LayZr, E3, etc all have farily similar maximum amp capacity before they overheat and spit tungsten particles in your weld. (in my experience 2% lanthanated will carry a bit more current than the rest).

There are quite a few charts online that list amperage ranges for tungsten electrodes but the problem is the maximum amperage listed is usually on the ragged edge of being too much.

I saw a Miller Electric tungsten chart that listed the maximum amperage of 1/16” electrodes (ceriated, lanthanated, and thoriated) At 150 amps.

My experience tells me not to weld at 150 amps with a 1/16" tungsten.

Whenever I get up around 120 amps with a 1/16" tungsten...even on DC, I notice  some sputtering and tip erosion.

That is why I have my own personal max of around 100 amps for a 1/16” diameter tungsten on DC…and about 80 amps on AC.

why chance it when it only takes a few seconds to swap over to a 3/32"?

When you weld near the maximum amperage range for any size tungsten electrode, you risk dumping tungsten in your puddle.

So here is a down and dirty chart that is more reasonable on maximum amperage ranges for tungsten on DCEN.

AC maximums are usually about 15%-30% less.

.020”- 20 amps max

.040” - 60 amps max

1/16” - 100 amps max

3/32” - 220 amps max

1/8” - 350 amps max

5/32” - 400 amps max

What about low amp arc starts?

It is true that using the smallest diameter tungsten to get the job done will usually help with crisper arc starts at low amps.

But correctly sharpening your tungsten and having a good ground connection help too.

I keep a 3/32” 2% lanthanated tungsten in my tig torch for 95% of my welding.

I sharpen it like a needle for really thin steel.

I use a more blunt taper for really thick steel and aluminum.

I have known folks who use a 1/8" diameter tungsten for all their welding.

That might make sense for a pipe shop or a job shop where you are welding thick aluminum one minute and stainless steel the next along with different thicknesses and different metals every day.

But for most folks, a 3/32" tungsten probably makes sense.

Rarely do I need to use a different Tungsten electrode Diameter other than 3/32"...it seems to be very versatile for a 200 amp tig welder.

But ...If I need to weld something paper thin, and I am not getting stable arc starts with the 3/32”, I might drop down to a 1/16” tungsten.

If I need to weld thick aluminum and need to go over 190 amps or so, I jump up to 1/8”.

There are always exceptions…but thats welding for ya.