On Sun, 18 Jul 2010 19:01:44 -0700, "Steve B"
wrote:


"RogerN" wrote


I plan to get a bottle of argon/co2 mix tomorrow and connections so I can
plug it in to power. I'll give it a try on auto body and see how it does.
It has pots for amp and wire feed, not stepped adjustments, I don't see
why it wouldn't work OK.

RogerN

I have found that with thin sheet metal, it is better to make a series of
tacks, rather than long runs, as those generally fall through. Use the
color as a guide. Make a tack, and wait until it cools down to yellow
fading away. From the available glow of the light of the puddle, you should
have enough light to already be positioned for the next spot. I do it in a
push situation, pushing the next puddle in front of the other, rather than
pulling the wire away. Got some mighty fine stitch welds like that, and far
less burnthrough. If you burn through, it's a bitch to fill up the hole, or
stop and make a patch, and the patches look like hell. Jump around and let
it cool inbetween spots to keep distortion low.

Steve

visit my blog at http://cabgbypasssurgery.com

Patching burnthrus is actually quite easy with continuous voltage
control. Just dial back both to where it works well for closing a
hole.

I would strongly recommend spending a couple of hours practicing
making and patching burnthrus on thin scrap. It'll be time very well
invested. Then when (not if) you get a burnthru, rather than cursing
you'll just grin with the thought, "no worry, mate, oy kin fix that
in a jif."

It definitely helps to have the metal bright clean. it is possible to
MIG weld thin metal that is dirty or has some surface rust or paint
residue, but it is not possible to get a good weld under those condx.
Gunnner is right on when he suggests having plenty of scrap practice
material at hand. I nearly always "calibrate my hands, ears, eyes
and machine" on a bit of scrap before I start welding for real if I
haven't welded for more than a few days.

That's not so true of TIG because TIG is so amenable to puddle
control, and independent real-time control of both heat and rate of
filler addition clear down to zero. It's less true of stick simply
because stick is seldom used on stock less than 1/8" and there's a lot
of latitude even with 1/8" rod and 1/8" stock.