A simple solution for re-spooling filament onto a spool! The re-spooler has 3/8-16 inch UNC threads incorporated into the design. Print the re-spooler wheels twice, and use a 3/8-16 inch UNC threaded rod or sufficiently long bolt with the same thread pattern to assemble. Thread on one of the re-spooler wheels, slide on an empty spool of filament, and thread on the other re-spooler wheel and tighten. I used a drill to spin up the re-spooler and transfer filament from a 2kg spool to an empty 1kg spool. I recommend using a TUSH (The Ultimate Spool Holder) or similar for the larger spool.

• https://www.thingiverse.com/thing:2047554
• https://www.thingiverse.com/thing:3885870

Additionally, as you can imagine, this re-spooler could be used for a number of things, not just filament spools!