"Tim Wescott" wrote in message
...
On 04/09/2011 02:19 PM, Ed Huntress wrote:
"Tim wrote in message
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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.

First, on regular skiving tools, which plunge in from the side of the work,
it's common when cutting steel to set the top of the tool 0.002" or so above
the centerline to get some effective top rake, or, more commonly, 0.002"
*below* the centerline, to avoid the need, in shallow cuts, for front
clearance. When wire EDM first came on the market, a lot of tools were made
this way, because you couldn't tilt the wire on those early ones. They just
left them square on the ends, with no clearance.

This probably means little when cutting aluminum and plunging from the end
is no place to try it, anyway. But if you like working with these tools and
try them from the side, particularly on steel, keep it in mind.

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-)

--
Ed Huntress