The Gear set transforms the power to torque.
It makes the Nimble so powerful and small. The 30:1 gear ratio is perfect for translating stepper rotation to pure filament pushing torque.
The Hob is the driving force in the Nimble. It converts the torque to filament movement.
The custom designed Hob is small, but the teeth have real grip and the shape holds the filament without generating too much chaff. The chaff that is formed, is easily removed because of the rounded grooves.
The set consists of the worm, the gear, and the hob.