I think that cardboard requires a drag knife,not a rotary cutter. I have log believed that a drag knife blade could be held in an unpowered spindle would work in a small cnc machine and did indeed intend to try this, but have never yet got around to trying it. My wife uses a a card cutting machine (craft robo) which works well for THIN card, sadly however the blade diameter is too small for my i/8" collet chuck. My intention had been to try to get one of my many (too many) broken 0.5mm cutters reground with an offset point, but the road ro hell is paved with good intentions!!! I still think it would work though. G.