Some geometric trickery is used here to make this a gear that will print well even on machines that, like mine, have poor or no buffering of GCodes and stop momentarily at the end of line segments.

Skeinforge will only record four line segments for the inner hole of the gear, and won't have stops midway up the gears, features not found in the Blender Gear script.

The hole is small enough (and on my machine got represented faithfully!) to thread with a 2mm post, making it a good candidate for building gearboxes.

EDIT: Uploaded a "test clip" file which can be used in conjunction with a couple of posts cut from a wire coat hanger to build arbitrary-length gear trains for test purposes. I found that a few washers in the right places can really smooth out the train.