Stepper Motor Gear

[MrDoom]

Interesting, I must try sharpening it then
As far as I know the steppers are meant to operate without problems up to about 80ºC, so they will seem too hot before they are even close to their limit.
You could also reduce the stepper driver current, I set all of mine to 0.8V and it seems to be a little cooler and has no problems printing.

[BernardRichhi]

For most extruders there's this little rotating gear that pushes against the filament inside the print head. This little gear is controlled by a step motor, and is kept right up against the filament with another spring loaded wheel to prevent slippage. When you create a 3D printed file, the slicer program generates a G-code, which tells the stepper motor controlling that little gear to rotate just a little bit each time it wants to print something, thus pulling in more filament and pushing heated filament out the hot-end.