Time to mount the motors! All the ball screws needed to be turned down on a lathe so that a standard coupler could be used to attach them to the motor output shaft. This is a very laborious and time consuming process that is probably best left to someone else. Being a masochist, I went ahead and turned them down myself on my mini-lathe. The outer surface, to about 1/8" depth, is extremely hardened steel. To the point that it cannot be cut with a standard bandsaw blade. It's really tough stuff.
The actual motor and ballnut mounts are made from welded steel plate, then ground flat on a plane sander. It is most important to get the mounts to a perfect 90 degree angle, as any adjustment in this dimension has to be done with shims. When completed I only needed a shim under the Y axis ballnut mount, which was cut out of a cheap auto parts store feeler gauge set.