Martin, thanks for clarifying the BCD/scaling issue.

From what I gather, Leadhead is planning on machining the gear, by mounting the blank flat on the machine I.e. so the gear axis and spindle are in the same plane.

If you've not seen it before, you might want to have a play with Gearotic (www.gearotic.com). It's written by Art (the original man behind Mach), and allows you to design/simulate all sorts of weird mechanisms. It originally started as just a gear designer, but has grown. The only limitation without a license, is you can't export different file formats, but if you do license it, it can produce various 3D file formats, or even generate the required G-code using either 3 or 4 axis.