Adapter to mount a filament spool on a thinner axle

This Thing makes an adapter that lets you use a narrow axle to mount a variety of filament spools on a 3D printer.

Filament spools, even from the same manufacturer, tend to have a variety of axle hole sizes, from small to quite large. If mounted on a 1/2" or 3/4" dowel as an axle, the mismatch between axle diameter and the spool opening will result in extra resistance, less filament being fed to the hot end and print quality problems.

A year or so ago, I made a bearing adapter to fix this