This is a variation based on the work http://www.thingiverse.com/thing:311515 . I found that it was difficult to find the hole for the filament. So I used Fusion 360 to recreate the part. I made it tall enough to stand above the top plate on the Rostock Max 2. I also tapered it to guide the filament to the hole in the bottom.
(You will have to revisit the original submission to get the nut that is to go on this.) no longer true it is all here now
Finally, I tried to apply a thread in Fusion 360 and it did not appear on the STL. If someone has any idea what I may have done wrong message me.
NOTE: 2/28.2016 9:20PM CST I got a note from a friend that I must have forgotten to check the "Modeled" box and that was the problem DUH.
Also be aware my printers are busy so I have not yet printed the update. I will attempt to do it tomorrow and supply feedback.
NOTE: 2/29/2016 17:23 CST.
I have had time to print the actually threaded version and it was perfect. I was able to use the knob it had tapped with the printed threads and the matched. You do not need to worry about printing it.
Note: 2/29/2016 20:35 CST
I even have the nut with the threads in it now. Honestly I had to use a tap on the one I printed on my Printrbot with PLA, but that may only indicate that I need to do some work on the settings for my printer. I will try it on the Rostock as soon as it is free.