On Wed, 01 Aug 2007 08:52:11 -0500, Ignoramus5693
wrote:

I have a copper bar that I am deciding whether to keep it (1x2x15"). I
cannot think of any hobby style need that would involve a copper bar
like that.

Very useful for welding thin aluminum sheetmetal corners without
blowing holes. The copper bar stops blowthrus by acting as a chill.
Lightly chamfer a corner on the copper bar to create a bit of space
under the corner to be welded. You don't want the bar to chill the
puddle right in/on the joint. Clamp aluminum pieces to bar with the
chamfer under the corner to be welded.
Weld away!

I make boxes by welding up pieces of sheetmetal, because I don't have
a brake to bend them. Even if I did, with welding I don't have to
worry about bending allowances to get the dimensions right.

It's even handy with thin steel sheetmetal, because weld-thru
(excessive penetration) won't stick to the copper; it'll just
reinforce the inside of the corner.