I finished 8 of the 16 parts (4 of 2 different designs, had 8 of a second design 1/2 done). Broke the flex coupling on the Y-axis. Woudl not be surprised if these were "home made". Just a cheap aluminum flex coupler. One bores did NOT match the shaft end (shaft had a keyslot, but coupler did not, so no key used). Both ends used miniscule set screws, and no locking compound. I am going to replace this one with an Oldham coupling and use a key on the shaft that has a slot. Will post pix later.