[Shop-talk] Annealing Copper bars

[David Scheidt]

On Sat, Aug 8, 2020 at 5:51 PM Jack Brooks <JIBrooks at live.com> wrote:
>
> Insulation - BINGO!  Great thought Donald!
>
> I underestimated copper's heat transmission rate.  Using propane, I could not get a 1/8 x 1 inch x 8 inch bar to get to glow with the bottom of the bar clamped in a vice.  I decided to try "Insulating".
>
> I laid a 3 inch long copper bar (typical busbar length) across the teeth of two sections of a coarse hack saw blade clamped off to the side of my vice.  There is almost no contact between the copper bar and these supports, only across the tips of the teeth on the two halves of the hack saw blades, so maybe a dozen pinheads.  With this arrangement and with a partially-dark room, I could just barely see the red glow in the copper. After a quench, the copper bar was soft!

That's a clever way of doing it.  A firebrick is the usual suface to
put things on while they're heated.  For a propane torch, you could
use a regular brick, or a cinderblock. They don't work with a welding
torch, because they explode.  Also, there's a surprising difference in
torch output.  A few years ago, I couldn't get a 1" copper fitting hot
enough to flow solder using the crappy propane torch I'd had for 20
years.   I bought a Bernzomatic TS-8000, at the advise of a plumber,
and it did it with out breaking a sweat.

>
> I now have a method.  Now I have to insure that I can clean up the contact surfaces well without affecting the flatness and I can go forward with softening the real busbars.

Sand paper or emery paper on glass will work well.
>