I did a Google search on "definition spiral", and after looking at a few of
the hits, below seems to
describe what need.

The site said difference between a Archimedean spiral and a logarithmic
spiral is that the Archimedean
has a constant distance between the spirals, whereas the distance in a
logarithmic spiral forms a geometric
progression.

Suggest you check it out.

http://en.wikipedia.org/wiki/Archimedean_spiral

Ace


wrote in message
oups.com...
An approximate spiral can be
cut by making half circles, each
one smaller by the difference of the
gap and the width of the cutter.

Great! Very simple.

I drew one with a compass...
I have a question... There are
two center points in this scheme,
one for each "side" of the spiral.
My drawing wasn't very precise,
so I cant get a good measurement
of the distance between these center
points.

1/2" cutter, 1/8" space between cuts,
11" diameter outer half circle (11" between
CENTER of cutter)

What will distance between centerpoints
be?


Rich