I did a short video to explain the most important features of my home made faceting head:
Btw, now it's not only the head, but actually the whole machine that I built myself. It does maybe not look as the fanciest one, but it was quite significantly cheaper than to buy a ready made one, and it is definitely subject to constant improvement.
Here are two stones - a smokey quartz and a simple glass marble - that I cut already with the new head. It was a tremendous saving of time and accuracy is great:
Edit 2017-02-15: Here's an illustration of cutting and polishing a glass marble to a standard round brilliant: