These bushings (range of sizes) enable grasping the rounded end or sphere of a spindle. Please see my video for an application on www.AsWoodTurns.com
From one end, the bushing is hollowed to accept a sphere of the given size. From the other end, the exterior forms a dovetail to fit many woodturning chucks.
Orient the print to prevent overhangs.
A given size accommodates a small range of sphere diameters.
For further instructions, please see my video at
https://www.aswoodturns.com/2024/06/eccentric-scoop/
The author marked this model as their own original creation.