Fidget Spinner - 3 arm with bearings
My son wanted a fidget spinner and I had some 8.5 mm steel balls around so made him this.
I printed it in two halves so that you trap the balls within rather than making them so they pop in.
Glue the two halves together. Takes a standard 608RS bearing
He also wanted a narrow button in the middle and domed so it could balance on his finger.
You will might need to rotate the STL so that you print so the outer part of the finger spinner are on the base.
Print the button slowly with a brim