Cutting a tiny keyway using the mill as a shaper.

[S_J_H]

ahh but that's the difference, I normally do not retract Z when surfacing with my mill.
It would not be to hard to build a solenoid triggered retract mechanism with exact repeatability and keep the Z axis rigid. Maybe in the future..

I did not pre-drill or even retract the Zaxis on any return stroke to cut that keyway.
Just a slow feed cut, return without moving Z, lower Z by .002" and repeat until it was done.

Steve