Modifying an M8 Extruder Stepper for Bowden Use

Update 6/3/19 The as-printed 2 mm hole at the bottom of the filament guide may be too small if you have to withdraw filament that has expanded just above the melt zone. I opened up the hole with a 2.5 mm drill and it is always possible to withdraw the expanded end of the filament from the extruder.

Update 2/24/19 I added a filament guide that should make it easier to thread the filament below the drive gear. It is sized to work with the smaller hobbed gear. If a larger diameter gear i