ceramic cups are the cast forms.  Sacrificial, get busted off.

Opening in the table top has to be smaller than the largest dimension of the cup top.

The cup needs to land in the opening of the cross plate.

The cup gets busted off, then the part gets placed into the opening, then the part gets 
"shell" knocked off.

opening should be round "horseshoe so the part can easily be slid in and out.