I was finally able to get back to this. I was dreading pulling the table back out because everything had to be undone. But it’s done.
The motor is not direct drive to the shaft. I was wrong. It attaches to some kind of gear box. I found that there are two set screws. None of the Allen wrenches I had on hand matched either screw. As per prior posters advice I will try to tighten them as soon as I remember to take a full set down to the layout room.
In the meantime here are pictures of the underside. 
