Aluminum will just melt out. I'd try the copper bar but leave it long
out both sides to give it some heat disapating ability.

The correct way to do this is have an EDM shop do the hole. Not expensive.

dave wrote:

I need to make a piece of sheet steel .250 thick, roughly postcard
sized, with a square-edged "through-slot" (perforation) in the center of
it approx .0625 wide by .750 long. in my shop, the easiest way would be
to weld two pieces together at both ends, grind flush, and leave the
slot 'open' in the center. can I stick a small sheet or copper in the
'desired open spot' and expect it to resist the 'buzzbox arc', when I'm
using 6011 rod? what about sheet aluminum? or is there something better?

what'll -resist- the arc temperature, not melt, and stay square? getting
the inside ends square again with a tiny jewelers file could take hours....

thanks guys for tips and ideas :-)

toolie