3d Printer CNC Router Conversion

[daveefordays]

I've seen a few random pictures of people converting their 3D printers to a CNC router / mill by replacing their print head with an electric drill motor and bit. 

It seems that generally printer frames aren't stiff enough to cut most things but acrylic and wood should be fine... Does anyone have any experience with something like this?

I also saw one where the guy had made his printhead and router head easily swappable so a few plugs and a few screws and he could switch between the setups.