This is a little hacksaw i made.
2 M3 screws are used for fixing the blade.
The blade is a 300 x 12.5 x 0.6 mm blade from amazon.
I stopped the printing after 3.2mm and lay the blade into the slot. Then i continued the print with the blade. That garante that the blade fits into the slot. However, if your printer is good in printing bridges, this is not needed. Do this on your own risk ;)