what wire size to use for lincoln 180

what wire size is best for a lincoln 180? I has .025 solid core now and was thinking about going up to .035

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.025" is fine and probably the best choice for really thin metal like auto body panels.

but for thicker stuff i like to use .035" wire.
there is something called "current density" and there is probably a really long definition but basically, you just cant get optimum penetration on thick metal if the wire is too small.

Some folks like to just use .030" for everything as a " one size fits all" solution.