This is a remix of the awesome Universal Filament Spool Holder posted by butchja (https://www.thingiverse.com/thing:2070272) which allows the use of pre-cut 5/16-18 x 6" all threaded rods or double end threaded studs like the ones I have linked in the parts section below - no no cutting is necessary. It also incorporates a mounting system for the Ender3 and CR10 Style printers which is based on the design from Skrutt84's Ender 3 - Filament holder DELUXE (https://www.thingiverse.com/thing:3114139). This thing includes an end nut which captures a 5/16-18 lock nut and covers the end of the threaded rod and nut. The end nut may help a bit with aligning the spool nut. I also modified the end thread on the spool just slightly, and modified the bearing spacing so t at the bottom of this description.

This version supports spools with up to 75mm holes (which should be just about any 1KG spool).

To assemble this:

1. I first put one locknut on the end of the threaded rod, with a few mm extra threaded through.
2. Insert the rod + lockunt through the Mount piece and make sure it is fully seated.
3. Assemble the bearings into the spool part, make sure they seat all the way in.
4. Install two washers and then the spool on the threaded rod.
5. Insert a 5/16-18 locknut into the "end nut" part, make sure it is fully seated. Add another washer to this end
6. Use a wrench to install the "end nut" with the the locknut installed onto the threaded rod, don't over tighten.
7. Have fun printing!

Parts list:

• 1x 5/16"-18 x 6" Black Oxide Steel Double End Threaded Stud, a 6" bolt (thanks for the suggestion ohheyitspaul) or all thread rod.
  https://www.zoro.com/te-co-dbl-end-thd-stud-516-18x6-oal-pk2-40410/i/G1031335/

• 3x 5/16" x 11/16" OD washers (a smaller OD than these may be better)
  https://www.zoro.com/zoro-select-washer-516-bolt-st-1116-od-pk50-514031g/i/G3525496/

• 2x 5/16"-18 Lock Nuts
  https://www.zoro.com/fabory-jam-lock-nut-516-18-gr-2-zp-pk100-u124230310001/i/G9009253/

• 2x 608ZZ (skate bearings)
  Amazon Item "B01C6OFIDQ" (please copy and paste the item in the search field at Amazon, you can read why below)

The parts are not oriented for printing, see the pics for a suggested print orientation. Only minimal supports (touching the build plate) should be needed on the end nut part.

The STEP file is included for easy re-remixing :D

If you want to use this spool holder with 2020 extrusions, you can grab one of the mounts linked below, which will also work with this (I designed these for a different spoolholder but they will work with this as well).

https://www.thingiverse.com/thing:3128309

Update 8/15/2020: Based on feedback, I understand that some 5/16-18 nuts are a bit larger than the ones I used (13mm vs 12.6mm flat to flat), so I updated the end parts which hold the nuts with slightly larger pockets (13.3mm flat to flat). Due to slight differences in hardware, I also added some 0.25mm bumps to the sides of these pockets, which is a compromise to fit the 5/16-18 nuts that may be slightly over or under sized. This change should make the nuts easier to install. I've tested the fit of the new pocket design for the 5/16-18 nuts I have, and it works. Bbut if you have a problem with the fit please provide some feedback, and if possible the flat to flat measurement of the 5/16-18 nuts you are using with this model. Note that if you find that both the nuts and the bearings don't fit, you should calibrate the flow and steps on your extruder since those will affect the fit. The updated version is "V6" and all the parts and STP file have been updated with this change.

1/23/2021 - I have removed any Amazon links, and instead provided the amazon item numbers in quotes. This was done as a small protest against the way Thingiverse edited my description, and installed their Amazon Affiliate links without notifying users that they were doing it. Sorry for the extra step of having to copy and paste the item numbers, but I believe they need to be clear with content creators about this. I did not originally post my own affiliate links here - they were "clean" Amazon links, but for some content creators here, the affiliate links are the only way they receive anything back for their work, and that avenue is now closed off. More info here:
https://www.thingiverse.com/groups/thingiverse/forums/site-issues-and-feedback/topic:49539

12/14/2021 - Updated the BOM and instructions to note where to install the washers. I added two washers to the side connecting to the printer (between the mount and the bearing inside the spoolholder), and one washer on the other end.

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Thanks for looking!