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?