This is a simple extruder I made for 1.75mm filament. The only things you need to complete is an insert for motor shaft and a 8 x 11 x 7mm Bearing and some 3mm screws.

It will fit a Nema 17 Stepper Motor and the famous chineese extruder. (the black one that you easily find on eBay)

Enjoy !

http://www.youtube.com/watch?v=sRRu5mCk6TQ&feature=youtu.be
http://www.youtube.com/watch?v=5AlZcp0Gpig