Has anyone used a pneumatic type pen on their homemade cnc?? If so, what are the pros to using it and what are the cons? Which one would you recommend? Do they make them to hold the standard 1/8" or 1/4" bits? Are the strong enough and fast enough to get the job done?

I looked at them but you need a much bigger compressor than I have, the rated flow rates quoted are normally for only short duty cycles.

Graham