Well everyone, I just got done with my junior machine design project for school and thought you all would probably enjoy this.
It's a quick change gearbox capable of tuning: .050in/rev, .010 in/rev; 12, 16,18,20, 24, 28, 32, 40, and 48 tpi. sorry, no metric here. It also has a built in quick change tool feed direction function.
I've done a complete design including fab drawings, stress calculations, fatigue life analysis, press fits, you name it. this could actually be built if someone were so inclined.