I intended to make the filament cutter from Vetterick, but my hardware store didn't have any suitable springs. Here is a remix of the design that doesn't require any springs or screws. Just 3 sections of a blade for 9mm box cutters. To put together slide the lid into place, lifting the slicing head over the edge. Then just push down to cut filament. The spring is fairly gentle, so it it's sticking down, just sand/scrape off the edges of the cutting head.
This cutter also includes a holder than can be screwed or taped to the top of your printer frame.