TIG filler rod size - criticality/sensitivity and conseq's

Hi all
I am feeling a lot driven nuts with my TIG welding, trying to qualify on stainless. At college we have no TIG filler rods less than 1.6mm
(63thou's) diameter, in any material. On all steels using 1.6mm sheet (63thou's) coupons, I find using 1.6mm rod causes a very stop/go weld. OTOH if I chop-off some 1mm (40thou) or 1.2mm (48thou) MIG wire and use that as filler for mild steel, all seems quite promising. Am I mistaken in thinking that you are taking a too big a "shot" of heat out of the weld pool when you dip the rod whose thickness equals the sheet metal thickness?
Ernie previously made this recommendation covering this thickness of material
> Base Metal Tungsten Filler rod Amperage > ... > 0.030" - 1/8" 1/16" 0.030" - 0.045" 15 - 90
so it would seem I should indeed be using filler rod of the dia. I am taking from the MIG machines.
Now all this is *^%%#$#d-up when I actually come to try to qualify on stainless steel, because again the smallest wire is 1.6mm and I cannot swipe wire from anywhere else. In my fillet welding I am having a damn' hard time trying to get a decent fillet without overheating the plates and causing melting defects on the back-surface.
Something I am finding difficult is getting the big rod into the melt pool past the tungsten while keeping the arc short enough to get tight into the corner and run a small (proportionate?) fillet while not touching / dipping / contaminating the tungsten with the rod.
Am I lacking experience to handle these rods which are just fine or am I trying to work against loaded odds?
Should I run to the welding store and buy some of these rods "out of my own pocket" in order to get the qualification done?
Richard Smith
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I do it all the time. SInce I can't get the other instructors to always buy 0.045" filler rod I have a few spools of MIG wire set aside. Just spool off a length and draw3 it through your fingers tostraighten.

Bring your own filler. Using 1.6 mm filler on 1.6mm materiel is doable, but a pain. Use some smaller wire.
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As well, .063" filler rod is hard to fit under a close tungsten, you sort of have to back away as you dip, then advance. .125" plate suits .063" rod, much less and it's .045".
-- David Algie Algie Composite Aircraft http://members.iquest.net/~aca /
http://groups.yahoo.com/group/algiecompositeaircraft /
wrote:

Amperage
90
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