[Shop-talk] Annealing Copper bars

[Jack Brooks]

David,

Thanks for the heads up on the Bernzomatic TS-8000.  I am using a 20+ year old all brass Bernzomatic head which has never let me down before, but it could be a contributing factor. It does put out a heck of a long beautiful blue flame though.

I chose to support the copper bars on the hack saw blade teeth because there is the least contact between the part and the support to wick away the heat. I was afraid that brickwork would absorb some of the heat.  I did unsuccessfully search my garage for some old refractory blanket. 

Cleaning - Good reminder about sandpaper on glass - Thanks.  I learned the "glass" trick when rebuilding a 1960 Triumph TR3 engine and took the crank thrust bearing down to the minimum specified gap by sanding a mismatched set of standard and oversized backing plates down on a piece of glass and also blueprinted the pump by reducing the pump rotor baseplate clearances on a sandpaper/glass setup. Great tip!

Jack



-----Original Message-----
From: David Scheidt <dmscheidt at gmail.com> 
Sent: Sunday, August 9, 2020 7:21 AM
To: Jack Brooks <JIBrooks at live.com>; shop-talk <shop-talk at autox.team.net>
Subject: Re: [Shop-talk] Annealing Copper bars

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.
>