Sometimes I want to use 2" "olympic" barbell plates on a 1" dumbbell. This adapter is a simple sleeve to allow that. You still need to make sure the plate itself is well secured to the dumbbell (e.g. by sandwiching it between two plates of the right size).

Printed in regular PLA, I have used this approach for four years with plates up to 15lbs (7kg) with no issues.

Included .f3d model is parametric on all important dimensions.

For printing, I use PLA or PETG. Three perimeters with a .4mm nozzle is enough to avoid infill and make it solid.