Over-the-top spool holder for monoprice/wanhao

Over-the-top spool holder for monoprice select. No more stick-slip knocking noises coming from spool holder.

- Self-centering threaded double wedge design.
- Big bearing at the nut end (6805)
- Little bearing on the cantilever end (R626)
- Zip-tie friction stabilizer

Bearings were selected because I had them in my old bicycle parts bin. I think they were old bicycle hub bearings. Worked out good. Printed at 0.1mm layer height to form the threads correctly.