This is another spider coupler I designed to eliminate "z wobble" (and for me a slightly bent threaded rod). Unlike similar designs, I found plastic & rubber spacers slightly rigid. I have included a mold to fill with a substance of your choice (i used bathroom silicone). Although the silicone is soft, I have tested z travel with a dial gauge and its spot on. I don't have the hardware sizes I used (sorry), but it is the standard Printrbot shipped hardware. I left the tolerances a little tight so it will require some cleaning.
I printed the parts as follows:
-2x bottom coupler @ 90% infill .35mm layer height (.35 is my minimum .50 will work fine)
-2x top coupler @ 90% infill .35mm layer height I used honeycomb support (my bridging is horrible at the moment)
-2x molds @90 % infill .4mm layer height
-Once you have all your parts printed fill your molds, level off with a credit card etc... and allow to dry (mine took a good 24hr for silicone to cure)
-Clean as necessary, you will need re-drill out some holes. You will need a small nut and bolt for each of the bottom couplers, and a large nut for each threaded rod (top coupler). The small nuts will fit in the bottom couplers very snug, some cleaning of the first layer is required before it will fin in.
-I made sure the nuts went into the top coupler very snug, then threaded rod with several layers of Teflon tape. (to prevent the threaded rod from slipping, you may want to tighten with tools)
-Finally I broke the thin walls off the mold and was able to slide it out easily. You may want to double check the center mass of the spacer (if you use silicone) as mine was still uncured in the middle.
-Assemble & enjoy
P.S...... I applied acetone to the outer layer with a syringe (especially the teeth) to strengthen it.