Wanted to make bearings fit into this spool holder I had already printed, so I made these little couplers that fit into the holes on the uprights, that also fit standard 608 bearings.

Print a simple rod to go between the two or perhaps find a long bolt that the filament spool can rest on. Since this incorporates bearings it should reduce most of the drag or pull.

Printed on the Delta Go at 30mm/sec with AMZ3D yellow PLA, at 205 degrees. I needed a brim (most stuff does on the Delta Go) but if you have good adhesion you won't need it.

There are two slight chamfers that will allow you to slide the bearings into the coupler, and the coupler into the holder uprights so these should simply be friction-fit. This exact size JUST fit into the uprights and fit the bearings perfectly, but my tolerances might be different than yours. I've included the SketchUp and DS Mechanical raw files if you'd like to tweak the diameter to match your printer's tolerances.

Designed with DS Mechanical.