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!

Rich Grise wrote:

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. ;-) )


Bull****. I've used it on 3" and 6" copper pipe in the cooling
system of a TV transmitter. Of course, you have to know how to solder
more than a couple twisted wires to do it right..

--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On Tue, 14 Sep 2010 18:43:59 -0400, "Michael A. Terrell"
wrote:


Rich Grise wrote:

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. ;-) )


Bull****. I've used it on 3" and 6" copper pipe in the cooling
system of a TV transmitter. Of course, you have to know how to solder
more than a couple twisted wires to do it right..
And sweat brazing works the same way - just needs a lot more heat.
Brazing is just high temperature soldering when all is said and done.

wrote:

Michael A. Terrell wrote:

Rich Grise wrote:

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. ;-) )

Bull****. I've used it on 3" and 6" copper pipe in the cooling
system of a TV transmitter. Of course, you have to know how to solder
more than a couple twisted wires to do it right..

And sweat brazing works the same way - just needs a lot more heat.
Brazing is just high temperature soldering when all is said and done.


The hardest part of that job was removing the fittings from the old
copper pipe. It wasn't soldered properly and had leaked so some moron
braised the pipe to the fittings over the leaks. I had to saw them off
flush, then file away the brazed spots. After that I had to use
Oxyacetylene torch to heat the fitting while shoving a wide, narrow
screwdriver between the old pipe and the fitting. Once it was pried far
enough I used a big pair of needle nose pliers to twist a kink into the
pipe and slide it out. Then I poured ruby flux on the hot copper and
added fresh solder to properly tin each port. The excess was wiped out,
then the ends of the piper were cleaned & tinned with plenty of 99.5%
tin, .5% Antimony solder. Finally, they were carefully lined up and
heated, then slid together. Only a couple needed a touch of solder to
get a smooth joint all the way around the pipe, and that was just for
cosmetics.

All that work because some idiot was in a hurry, and the custom RCA
parts had been out of stock for over 20 years.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On Tue, 14 Sep 2010 18:43:59 -0400, Michael A. Terrell wrote:
Rich Grise wrote:

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. ;-) )

Bull****. I've used it on 3" and 6" copper pipe in the cooling
system of a TV transmitter. Of course, you have to know how to solder
more than a couple twisted wires to do it right..

No, you're right - I've never had any problem sweat-SOLDERIMG; the
question was about sweat BRAXING, which I take to be somewhat of a
different animal.

But thanks for sharing!
Rich