Today I started working on an ABS extruder head. I used a pinch roller design similar to the one used by RepRap here. Instead of 3D printing the body, I cut one from plywood on the ShopBot. Here's a picture of the cad drawing:
I'll try to take a picture of the real thing sometime soon.
I ended up knurling the stepper motor shaft on the lathe, managed to get the rollers assembled. Using a NEMA 17 motor at 50% current, I managed to get about 60 in/min filament feed rate. Right now the motor stalls before the ABS filament slips which I guess is good. We'll have to see if it can generate enough force to drive the hot part of the extruder.
I also ordered a bunch of other parts for the rest of the extruder today. Those should be here in a few days...