For Christmas this year we were giving my nephew a Viewmaster. While there are plenty of discs out there, they seemed dated to me. So I went about trying to make my own by finding pics on the internet. These parts were designed so that I could cut the overhead projector sheet circles using an Exacto blade, the type with the flat tip, that was heated to allow it to be melted through the slot in the cutter part. I used a 5mm bolt and nut. The same base part us used to do the cutting on and then also used to as the bottom of the clamp which held the hand cut card stock discs together while the glue sets. These were printed at 0.28 mm layer height and 10% infill.