On 9 Jan 2006 17:35:47 -0800, "Ardilla Volante'"
wrote:

I need some help.


I am making a gigantic " weather vane type thing" (technical term?).

(some very thick material and I am slightly intimidated)

its made up of 4 arms coming out radially from a central bearing unit.

the arms are a mix of rectangular tubing (6" x 2" x 1/8" thick.) and
3/8" plate.

the central unit is machined from a round of 12" 6061. it rotates on a
hardened point with a delrin collar.

I need to stick the arms to the bearing. The two pieces mate on a
flat groove vertically along the bearing.

____the question______

is the extra penetration gained from using Ar/He worth the extra
dollars?, (we've been using straight Ar)

also, aside from oxy acetylene, what pre-heat methods have any of you
had luck with?

any help would be much appreciated.

It seems to me that penetration is only an issue if you're trying to
weld clear thru something. I think if you can get a puddle going,
you can make a weld. What difference does it make how deep the
puddle goes into the metal, as long as the pieces are fused together?

So I would think that if you can get a puddle going on the 12" round
with argon, you can weld it -- and if you can't then try a hotter gas
mix or a bigger welder.