On Sat, 09 Apr 2011 22:39:06 -0400, Ed Huntress wrote:

"Tim Wescott" wrote in message
...
On Sat, 09 Apr 2011 18:27:27 -0400, Ed Huntress wrote:

"Tim Wescott" wrote in message
...
On 04/09/2011 02:19 PM, Ed Huntress wrote:
"Tim wrote in message
...
On 04/09/2011 10:20 AM, Ed Huntress wrote:
"Tim wrote in message
...
On Sat, 09 Apr 2011 12:41:01 -0400, Ed Huntress wrote:

"Tim wrote in message
...
On Sat, 09 Apr 2011 00:32:29 -0400, Ed Huntress wrote:

"Tim wrote in message
...
On Fri, 08 Apr 2011 23:16:17 -0400, Spehro Pefhany wrote:

On Fri, 08 Apr 2011 23:08:55 -0400, Spehro Pefhany
wrote:

On Fri, 08 Apr 2011 21:38:25 -0500, the renowned Tim
Wescott wrote:

I want to make a bunch of identical molds, for 3/4"
diameter model
airplane wheels.

I'm envisioning a tool that's 3/8" across, that I just
sharpen up,
grit my teeth, and push into a spinning piece of aluminum
to make
my desired profile.

Is this a sensible thing to consider? Is there some other
way (short of CNC machining) to easily duplicate cavities
in the ends
of a bunch of aluminum tubes?

Since you got me started on this, g here are two other things to
consider.

The other point, about your workpiece material: It looks like you're
machining wrought barstock, probably 6061 or 2024. I don't know the
figures for 6061 but in 2024, the thermal conductivity in the T3 or T4
state is roughly half that of the same material in the annealed state.

I'm sure you won't be annealing the material just from heating the
foam, but if you have in mind to anneal the tool first, to get better
conductivity, keep in mind that the material will revert to the
tempered state in a couple of hours if you don't give it a full
anneal.

Neither of things probably matter, but I hate to leave details hanging
around, just in case. d8-)

It is, indeed, 6061, heat treated to some three or four-digit code with
a "T6" at the beginning. So I'm assuming that for my purposes it's T6.

Yes. The other codes have meaning, but they aren't relevant here.


I'm mostly thinking of heat conductivity in competition with plastic or
wood. Since the current process involves clamping up one mold with a
pair of vice grips and tossing the assembly in the oven for half an
hour, I can't claim that speed is of the essence. Before I start
worrying about the thermal conductivity of the aluminum I should think
about better ways to conduct heat _to_ the aluminum, like fins and a
fan in the oven, or immersing the mold in boiling water, instead of
putting it in a still-air oven.

How hot does it have to be?

Damned if I know. I _do_ know that if I bake it for 30 minutes at 150
degrees it forms, but doesn't seem to do so as well. If I bake it for 30
minutes at 200, it works better. I should try 250 -- I expect I'll melt
the plastic, but that'll be a learning experience, right?

--
http://www.wescottdesign.com