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Hi James. Yes, touching or scratching will contaminate the tungsten point,
but I haven't had any problem with that. Many machines (like mine ) have a
hi-freq "start" mode, turning off the hi-freq as soon as a stable arc is
established. Still, I seldom use it. The amount of contamination that gets on
the tip is so minimal it doesn't affect the arc.
When you are welding, metal actually vaporises up off the puddle and gets
on the tip anyway. With aluminum, the oxide pops up. With steel, the carbon
comes out. With stainless the chromium separates.
All of these get on the tip. The trick is to move the weld puddle along
quickly to minimize the time the metal is in a liquid state, so the
alloys can't separate. Frank D.
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