M8 Rod Stepped Headset Cup Press Cone
A stepped press cone with eight 4 mm-tall lands from 58 mm down to 30 mm diameter (2 mm-wide ledges) and an 8.3 mm bore that slides onto M8 threaded rod. Print two and clamp them with nuts and washers to seat or square bicycle headset cups, bottom-bracket cups or bearings. The step just under the cup's inside diameter centres it, and the next ledge pushes on the rim, so it works across the 30–58 mm range without depending on any one cup standard.
tool bicycle headset bearing-press