What is the minimum size of router bit you can use with a small CNC routing/engraving table?

cnc router
Antony G asked:

I considering buying a cnc router table (max material cutting size is 1200mm x 800mm x 90mm). The website indicates the blade holder specfications are 3.175mm, 4mm & 6mm. Does this mean that the minimum router bit size I can use with this machine is 3.175mm? Basically, I want to cut narrow straight slots in a sheet of MDF and I need them to be as narrow as possible. Does this mean that this machine cannot cut slots more narrow than 3.175mm?

Finally, the sheet of MDF would be 30mm thickness. If the machine was to router/engrave completely through the sheet e.g to a depth of 30mm, would the cut be straight and clean with no tool marks on the cut sides of the MDF? Would a router bit with a thickness of 3.175 struggle to do this?

CNC Router