"axolotl" wrote in message
...
On 1/19/2010 7:43 PM, Pete C. wrote:

I expect you probably have to break it down into 4? separate arcs and
cut each one in a separate setup with the part and mill positioned the
proper distance from the center of the rotary table.

I was looking at the 5 centered arch graphical method, thinking that given
an ellipse bounded by a rectangle, one could mathematically determine
offsets and radii. My head hurt. It then occurred to me that someone in
the bad old days before CNC must have done this. Hence my appeal to the
collective knowledge pool.

Kevin Gallimore

If you really want to do it mechanically without moving two axes
independently, you need two rotary tables mounted one top of the other. The
top is offset by half the distance between the foci of the ellipse. Then
rotate the two tables at the same rate.