Second and working version cleans up the sizing issue (think I used diameter value as radius in OpenScad initially) so it is printable on standard ToM/Cupcake. It accidentally turns out to be an interesting design for calibration and testing.

This is an index plate for a dividing head (http://en.wikipedia.org/wiki/Indexing_head), used with subtractive processes on milling machines or lathes. Wanted to see if I could make a plate with more and different combinations of holes than were available, but still compatible with the dividing head.

The rings of holes are primes (13, 17, 19, 23, 29, 31, 37, 41, 43, 47). You can use a geared mechanism to divide a circle into any number of parts. For example, making a N-tooth gear, or cutting M faces on a solid. For an idea of how they work, see atmpage.org/contrib/JSAPP/divide/divhead.html or gearcutting.blogspot.com/2008/02/dividing-head-settings.html.

This is the first step in building a simple dividing head.

Big thanks to Doug (http://www.thingiverse.com/dougc314) for helping cleanup and print.