Hi Gaston, is what Paolo wrote above what you were asking for when you mentioned "skeleton font" (font with bones in it), or were you asking about something else like getting fonts that are made up of a single central line instead of for filled text.

Normal TrueType fonts are set up to be a filled area instead of a single central curve line, but I think that there are some out there for CNC that are made up of only central lines and not filled. To find some you might try a search for something like:
"single stroke" truetype

I'm not entirely sure if those will work properly with MoI, but I think probably so if you choose the "Create: Curves" option.

When you use the Draw solid / Text command to create text geometry, that Create: option is near the bottom of the options panel, by default it tries to create solids but you can set that option to make it create only curves instead which sounds like it may be what you need in this case.

- Michael