When the sphere is formed the cutting cartridge 1 is replaced by a small tool rest 9 in order to cut a groove to partially part off the tennon.
While doing this the brake 10 is locked.
The same can be done on the other side.
Turn the sphere turn it through 90° rechuck it by mounting it between a homemade wooden cup chuck and a tail chuck 11.
Reposition the bottom plate to the new centre by using the precision stop 12.