I needed a cutter/punch that could cut circles out of paper, polyfoam or whatever. I use it for archery target, but it can be used for anything you want.

I have designed two versions, one cutting 120mm diameter circles the other 60mm.

I have two models uploaded, one I use a  threaded insert, the other you can screw the screw into the material.

You will need:
M5 threaded insert (7mm x 5mm)
M5 screw
3mm diameter nail
9mm scalpel blade

Caution! Risk of injury, use with care!