I got annoyed with my thin solders not coming nicely off the spool (the solder was fine enough that it would often go under the spool, kink and otherwise just be a pain.

Here is my solder spool holder 3D printed on my Bukito. I used some skateboard bearings (608 - 22mm OD, 8mm ID, 7mm thickness).

8mm = 0.315” and 5/16” = 0.313 so I used a piece of 5/16” wooden dowel

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And here it is with the solder roll:

Now the solder comes off nice and easy.

I used #4-40 x 3/8” flat head screws to hold it together, but I imagine that M2.5 should work as well.

I uploaded the FreeCAD source files, and .stl files to: https://www.thingiverse.com/thing:515131