I'm having some trouble with the cut. I'm using 3mm plywood from the hobby shop. It must have hard spots or knots on the inside layer. I've broken 3 bits. I'll have to go back to the store and get some thin basswood.
I'm trying to cut these with a .0312" router bit and am having trouble with the fit up. The pieces are loose an not fitting tight. I've tried to offset the cut and it's worse. I guess I don't quite understand the way offsets work. I also have some new 1mm bits I could try out. I guess they are about .0394".
I've never used a CNC router myself but I've done a fair bit of DIY in my time and have broken many a 1mm drill bit. Even 2mm drill bits are quite easy to break unless you are careful.
I suggest that rather than break some more 1mm bits you use a thicker router bit. Maybe about diameter 3mm or 1/8th inch - 0.125" maybe.
My webpage - (which is taking a few minutes to load up because the free hosting server is overloaded)
http://scot.tk/trispokedovetiles/trispokedovetiles-CNC.htm(Once you get it loaded up it might be an idea to "save page as.." and run the webpage locally in future)
Anyway that "Trispokedovetiles: CNC code to cut tiles" webpage has got an option to generate CNC code for router cutting for any size of router bit, though you must input the dimensions in mm.