Upcycled spool for filament refill

Design for reusing an empty spool for filament refills.

Parts needed:
- Empty filament spool
- 3 threaded rods M4 cut to a length of ~10mm longer than the spool width
- 6 M4 nuts (I used self-securing ones)
- 3 printed spool clamps with pockets for M4 nuts
- 3 printed spool clamps (counterpart)

Take an empty filament spool and cut it into two halves. In my case the spool was made of two parts making it easy to cut along the weld using a hacksaw.
Fit the M4 nuts into the spool clamps