This is the stock gear that comes on the Ultimaker Stepper motor. Modified for printing in ABS. If you are like me you have to mash your first print layer to get it to stick, which will flares out prints. I compensated by tapering the bottom.
I also adjusted the model to account for ABS hole shrinkage.
Print with single wall .4 thickness. 100% fill.
Push onto stepper shaft. (it's a friction retention piece)