Don Foreman wrote:
On 12 Sep 2005 10:59:10 -0700, "ed_h" wrote:

I'm making a steel-post-and-stainless-cable railing for my deck. The
posts are standard 1-1/2 inch pipe. The cable will be attached with
swaged fittings at the end and corner posts, but will simply pass
through holes in the intermediate posts. I want to keep water from
getting inside the posts where the cable passes through, so I plan to
drill through the posts, and insert a short stainless tube across the
dimeter of the pipe. I've experimented with both brazing and soft
soldering the stainless tube in, and both appear to work, but the
soldering is much easier. Also, the heat needed for brazing tends to
melt the end of the stainless tube (5/16 OD, 1/4 ID), so the soldered
job looks better, too. The posts will be painted.

So here are the questions:

1. Will the soft soldered joint take normal outdoor Nebraska thermal
cycles (-20 F to 105 F) without cracking over time and allowing rust to
get a foothold? There is no real mechanical stress to the joint other
than from temperature changes.

2. Are there soft solders that are stronger than those for plumbing?

3. Should I consider something else, like hard solder (I think this
takes a temp as high as brass brazing, doesn't it?) or epoxy?

A tin-silver solder works great on stainless, provides good color
match, is considerably stronger than plumbing solder and works at low
temperature -- about 430F. Harris Staybrite is one such material.
Flux can be Harris Staykleen or ordinary tinner's fluid.

It will handle thermal cycles. It's used in refrigeration and in
food & beverage applications. Joints must fit well; it is quite
fluid and doesn't "bridge" gaps well. Staybrite 8 is a similar
material with higher silver content, will bridge gaps better because
it has a plastic range. It's harder to find, though.

A stronger material would be a silverbrazing material. It may not be
a good color match because most silversolders contain some copper,
and you'll get some discoloration of the stainless from heat. It
runs at about 1200 to 1400F. It'd be stronger than you need here;
I'd go with the Staybrite.

Thanks for the lead. I researched Stay Brite. It is a little hard to
find, but is available mail order, anywhere from $50-$90 for a one
pound spool. However, McMaster carries a silver/tin solder with just
about exactly the same composition (from the MSDS sheets) for about
$35. If anything, it has slightly higher silver content. It doesn't
list a brand, but I wouldn't be surprised to see that it is Stay Brite
when I get it. They also have a flux that appears to be very close to
Harris Stay Clean (again from the MSDS sheets). Thanks for the advice.