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I was having trouble with my extruder motor skipping when I tightened the bolts and when I loosened the bolts, the motor would stop skipping but the filiment rollers would skip. Is it the easydriver current limitation? Do I need to increase its current? Is it the voltage drop over the small long motor wires? No, although these may power through the issue, the real culprit is the gears bind on the shaft. I thought I would add a washer to correct the problem (but easier solution below to check first). [youtube]http://youtu.be/vwGkWiJIKnQ[/youtube]See the video.

UPDATE: Not mentioned in the video is to first check that the bearing is fully seated into the large gear. I thought I had done this but by placing the large gear and bearing into a vice and gently hitting it with a hammer, I was able to set it enough to resolve the problem! Lesson Learned: double check the clearance and ensure the bearing is FULLY seated into the gear. Thanks.

Yep the "is it fully seated thing" caught me out when I first built the extruder.
You assume that flush with the gear face is properly seated but it isn't.
It should turn easily with not rubbing if it's assembled properly.