Cutting (perfect) circles out of paper or cardboard are not easy if you use scissors. With this rather simple construction, it is a piece of cake. I used 5.2 mm pertinax (phenolic paper) I got from a donor. It's very hard, still good to work with a cnc if you have a single flute end mill. Parameters are small depth per cut and fast cutting speed. Don't forget to engage a dust collection as the fine dust is not exactly healthy.

CircleCutter, 5 mm Pertinax Detail CircleCutter, 5 mm Pertinax Using the CircleCutter CircleCutter 3-D-model

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