School's over, so it's time to catch up on documentation. The lathe isn't finished yet, but I've made a lot of progress. Sadly, I won't have shop access this summer, so the lathe won't get finished until August or September.
The compound was made from two pieces, a dovetail slide which holds the ball nut, and a cone-shaped base. The two pieces were silver-soldered together.
The base of the slide had a ring milled in it with a rotary table, so that the force clamping it down to the cross slide acts at a maximal radius:
The cone is clamped pulled down by a pair of set screws, the ends of which are turned to 45 degree cones:
The carriage, compound, and cross slide assembled on the bed of the lathe: