Description
This is a universal spool hub/holder designed to make spool change-outs quick and easy.

• Three "bolt" lengths available: Original, Large, Extra Large
• Accommodates spools with a center hole of 50mm - 65mm
• Print the "Enbiggener" to expand this size up to 85mm
• Other sizes available using parametric Fusion 360 file included
• Can be used with or without 608 bearings
• Designed with printability in mind - no supports required

Changing the spool is a breeze as it is essentially a giant nut and bolt with cone-like faces, and the nut threads on very quickly due to the coarse thread pitch. Once the hub is mounted on the spool simply slide in a piece of 5/16" or 8mm rod.

Have spools with a inner diameter greater than 65mm? Instead of customizing and printing an entirely new spool holder just print the "enbiggener" instead (2x). This expansion sleeve slides over the "nut" and "bolt" pieces - increasing the capacity up to 85mm.

Mounting Options
Personally, I have an Ikea ALGOT wall shelf above my printer and I just have the 5/16" rod cantilevered out from one of the support brackets (it fits inside the bracket itself). The "nut" part faces the side away from the shelf which lets me change the spool without removing the rod.

There's also a few designs out there for this spool holder to allow for free-standing and mounting to an i3 style printer frame. Here are a few that seem to be popular (thanks to UncleManuel and cyberreefguru for making these):
https://www.thingiverse.com/thing:2821355
https://www.thingiverse.com/thing:2026642

For any of these mounting options, you can optionally pre-load the bearings by threading a lock-nut on either side of the "bolt" to adjust the amount of free-wheeling during a print.

Customization
Although the included .stl files will accommodate spools with a center hole of 50mm - 65mm, I've also included a parameterized Fusion 360 file so you can tweak the dimensions and lengths as required, or customize the bearing / axle tolerances etc. The minimum size that can be accommodated is 40mm due to the size of the bearing and threads.

Attribution
This thing was inspired by the cone-like hubs such as: http://www.thingiverse.com/thing:767317 (by rowokii)

and the bearing insert design is from: http://www.thingiverse.com/thing:605360 (by AndrewBCN) which lets you extract the bearing if required.

Change log

2016-01-03
Initial upload

2016-11-24
Version 2.0 now available. Added a chamfer to the threads on both the nut and bolt to make them easier to engage. (Using rriosq's method described on the Fusion 360 forum here).

2017-12-04
Large and Extra Large "bolt" lengths now available!

• Original for spools up to 75mm wide (print height 105mm)
• Large up to 110mm (print height 140mm)
• Extra Large up to 140mm. (print height 170mm)

2018-06-29
Added suggestions for mounting the 5/16" or 8mm rod (thanks to jayjr1105 for asking the question)

2018-11-01
Added the enbiggener to increase ID size capacity to 85mm

TODO: the enbiggener does not stay in place very easily until it is tightened against a spool - I plan on adding a small detent so it "snaps" onto the spool holder (catching against the bottom chamfer) but haven't had time to do so. If anyone is keen on doing this themselves before I get around to it please feel free to do so and I can link your remix.