Lens hole cutter for foam insert. Stock 64mm hole for 50mm Nikon lens.

thingiverse

I decided to make my own hole cutter for foam inserts to fit my lenses perfectly. It was designed to start in the reverse setting to get the cut started, and then switch to forward setting to finish off the hole. It's easier and cleaner than a carving knife, and less expensive than getting a hole saw from the hardware store. 64mm is the outside dimension. The one you see pictured does not have the top edge sharpened like in the model, I figured that would give an even cleaner cut, also go slow with the drill to start