On Sun, 12 Sep 2010 15:16:24 -0700, Tim Wescott wrote:

Needed to join two pieces of mild steel today, with minimal bead and as
strong or nearly so as the parent metal.

So I got each one hot, got a thin coating of brazing rod melted onto
each one, then slapped them together and heated the back of the
accessible piece.

Poof! Instant bond. What a joy brazing is.

Is this an accepted procedure? Are there any pitfalls that I should
know of? How likely is it that I've got a joint that's mostly flux?

(It's totally not anything-critical, except that it's part of a stand
for painting a model airplane -- so the worst that will happen if it
fails is that the air will turn blue.)

I've only brazed one time, and I had very good "coaching"[1] - it was a
car part where an "L" bend had opened on the inside.

When I first started to try to braze the part, I assumed that the braze
metal would act something like solder, but tougher. No such luck. One
of the "coaches" said, "You have to puddle the iron."

Imagine my surprise when the braze lasted the rest of the life of the
car! I was amazed.

But I definitely got me doubts about "sweat-brazing," primarily because
it brings to mind sweat-soldering, which is trivial to do, works, and
doesn't need an OA flame, but it's only useful for electronic circuit
components. (and "brazing" doesn't seem to work that way. ;-) )

Cheers!
Rich
1: a handful of guys who knew their stuff all advising me simultaneously!