Good illustration but wrong terminology. Spiral does not apply to either.
They are both helixes.

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On 01 Jul 2004 17:45:24 -0400, DJ Delorie wrote:


Steve Knight writes:
http://www.byrdtool.com/

Ok, I checked these folks out. Since the cutters aren't square to the
axis, they can't make a flat surface (the cutter corners are slightly
futher away from the center of rotation than the center of the faces;
they should make shallow beads and leave lines on the wood). Can
anyone explain what they were thinking, and/or how this really works?


http://www.byrdtool.com/Difference.gif