Quote Originally Posted by iBeta View Post
Maybe this is impossible, but thought I'd ask.
The word Impossible doesn't exist on this Forum.

This is simple thing to make. Just linear rails with spring pushing down for tension. The depth is controlled with the adjustable height plastic depth control.

Daft as it sounds you could just remove power from your Z axis stepper so there is no holding torque. Fit strong spring to pull down on Z axis then fit plastic collar to the tool to control depth.!! . . . .Instant depth control.