Update: 2/13/2017 - A fully threaded nut has been added based on a couple of requests.
Update 4/14/2017 - A revised version of this was created to ensure the bearings don't stick. It can be found here: http://www.thingiverse.com/thing:2248245 (by xjedix)

This spool sprocket is intended to make removing a spool of filament super easy, as easy as changing tires in NASCAR competitions, (I wish). No really, it makes removing nuts a thing of the past. It works with standard 608ZZ bearings or without, your choice. See my spool holder as this is a perfect complement to that holder but it works just as well with most other standard spool holders. (My bearings were a nice tight fit. Use the power of muscle persuasion or maybe a shop vice in a worst case scenario.)

Visit http://www.thingiverse.com/thing:2009565 for my top mounted spool holder.

For a bigger/longer version of this thing visit: http://www.thingiverse.com/thing:2075777
Changing the filament is five EASY Steps:

1. Remove nut(s) from one side of the spool threaded rod and insert the "Spooler Bolt." Fasten the nut(s) back on. You will never need to remove nuts again! I use 2 nuts on each side to lock them into place.
2. Place your desired spool of filament, (with filament unlike mine) in place. The rod and spool can both lay on their side.
3. Drop the "Spooler Nut" into place.
4. Spin tighten the "Spooler Nut" onto the "Spooler Bolt." Because I used a minimal number of threads on the nut, it spins as easy as a butterfly nut. This makes tightening the nut, a real cinch. Hand tighten the nut and bolt to finish clamping the spool into place.
5. Mount your "Spool Sprocket" on your printer's spool holder and center it.

Done!

To remove a spool reverse the steps above but skip step one. You're now qualified as a NASCAR technician. Now go change some tires!... I mean spools!

This spool sprocket should work for many types of filament spools. If it doesn't work for you, let me know in the comments and I'll see if I can accommodate your needs.

NOTE: This spool sprocket can handle a spool with a 30-65mm opening and 102mm wide. I implemented those dimension to suit my own needs. Feel free to use your slicer to adjust those dimensions to meet your own specific needs.