A beginner should be able to facet a 10 mm. I cut the end off a clear quartz crystal. Since it was basically round I rough shaped it into a 15 mm. I chose a big crystal to preform so I could see what I was doing. Late winter in Idaho isn't very warm.
Wet hands get cold fast outdoors.
At the facet machine, the parts catalog told what an index gear was, but not how to disconnect it from the arm so the arm and dop can rotate freely on the lap. The instruction book said to do just that, with the arm set at 90 degrees. It stayed disconnected. The arm spun freely. The instruction book said to set the angle at 45 degrees with the bottom of the 45 degree table attachment flat on the lap, then put in the stone into the table attachment.