This is an engraver attachment for one of my 3D printers. While it is not likely that it will be directly usable on other printers, it should be able to be modified for other devices. The engraver works wall and can be seen in action on https://www.youtube.com/watch?v=Jz5oezLPVYU
This device is suitable for engraving things like PCBs, signs, etc. and also for engraving although limited as to depth of the engraving. It can also be used a the batch drilling machine for PCBs and similar projects.
As most 3D printers have open mechanical works a vacuum nozzle has been included to keep the swarf from doing any damage.
There are instructions for assembly, drawings,the  and a parts list in the thing Files

I have added an upgraded carriage for this to take a Proxxon Micromot IBS/E instead of the Proxxon Micromot 50/E
When I tried to do some isolation routing for a PCB I found that the lines were too broad and this was caused by the bearings in spindle motor having too much radial play. The milling attachment can now give isolation tracks of close to 0.15mm.