On Sat, 09 Apr 2011 00:32:29 -0400, Ed Huntress wrote:

"Tim Wescott" 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?

Hobbing?

P.S. Not the gear-making process, this one:

http://tinyurl.com/hobbing

Well, the cavity is cylindrically symmetrical, so I'm not sure that
"hobbing" is the right term.

It's probably been a screw machine operation since 1920, or at least
some sort of tracing operation.

Sigh -- I'm always behind the curve.

I must be dull tonight, but I can't visualize what you're doing. Are you
talking about some kind of forming in the axis of a spinning tube, or
turning the outside diameter to a profile?


Let me know if you can see this, it should explain:

http://www.hippocketaeronautics.com/...rum/index.php?
action=dlattach;topic=5869.0;attach=53766;image

I'm not so much interested in the flange around the outside as the wheel
profile on the inside.

Per Pete and Karl I guess I'm looking for a form tool, but one that gets
applied in the axial rather than the radial direction. I'm not so
interested in cutting the mating flanges -- that's both easy enough and
persnickety enough that I should do it by hand. It's getting the tire
and hub shapes cut repeatably that interests me.

So I guess the real question is: should I be able to do this with a form
tool, assuming enough rigidity in my lathe?

--
http://www.wescottdesign.com