Simple Z axis Couplers

#A simple yet efficient Z coupler !
It works with 10mm M3 bolts & nuts.
There are 2 couplers :
- One is designed for **5mm motor shaft / 8 mm ACME rod** : Z-axis-coupler-5x8.stl.
- One is designed for **5mm motor shaft / 6.4 mm ACME rod** : Z-axis-coupler-5x6.4.stl. This coupler is ment for **Printrbot Simple** & **Simple Metal** printers but work perfectly fine with **other printers** with 6.4 mm ACME rod.
- One is designed for **5mm motor shaft / 5 mm ACME rod** : Z-axis-coupler-5x5.stl.
[Update 03/09/15] : fixed the screw axis closer to the body for a stronger grip on motor shaft & Acme rod (all versions).