Centered Z axis coupling Rev2

I had problems with the original Z coupling nuts being too loose and not being able to tighten down the jaws all the way, so I made the models 0.6mm bigger and this allowed for a tighter fit and a workable model.

If your printer is not calibrated, or you're looking for simplicity without a lot of post process cleaning up, this is not the z coupling for you. There are more simple, stronger, and less fragile designs that are easier drill out a centered hole without much headache such as Mhelmreich's design: https://www.thingiverse.com/thing:2603098, and the remixes that followed. Search for the one that fits the type of motor shaft (slotted or smooth) and for the type of z threading that you have.

This is to allow those facing problems whom have already printed their hardware to reuse some of their parts and are simply taken to this particular design.

The longer versions allow greater clamping forces so long as your printer has the clearances to accommodate them.