Bearing

Bearing

            Large “Print-in-place” Ball Bearing (Ø145mm) (barspin) / CC BY-SA 3.0
Knurled Bolt

Knurled Bolt

    Knurling bolt and nut (akira3dp0) / CC BY 3.0
Bevel Gear

Bevel Gear

    Spiral bevel gear (GeneralRulofDumb) / CC BY-SA 3.0
Elliptical Gear

Elliptical Gear

        Elliptical Gear Set with connecting links. (PerryT) / CC BY-SA 3.0