5mm to 8mm coupler

This the latest revision of my 5mm to 8mm shaft coupler. This design has a reduced overall size for limited space.
It also intended to protect your Z axis in the event of a crash. The coupler should fail before your Z axis is driven through your build platform or end stops when it encounters significant resistance. I have tested this coupler on a printrbot Plus V1 and a Prusa i3 with good results.

The revision 8 couplers are designed with two locking screws per shaft and are intended for higher torque requirements. These are not the damage preventing type. I will upload the revision 9 version soon that will incorporate a damage reducing failure feature.