Quote Originally Posted by olderdan View Post
It could be more of a radial cam shape as in a ic engine rather than a simple eccentric
The guy that made the video said; "Cam is circular and .06" eccentric, providing 1/8" retraction."

I was thinking the same thing about an engine type cam lobe.
Clearly you want a snap action mechanism that retracts the cutting tool quickly. But it if did do it at a fixed rate, it would leave a nice finished thread pull out groove.