This is an expanding arbor clamp I designed and tested to allow printing staff to hold stones easily while dipping into the hydrographic printing tank. The concept is that as you tighten the eyelet bolt, the fingers of the arbor clamp splay outwards and grip the stone from the inside. This is printed from a more flexible PETG and keyholes are added to try to alleviate cracking problems:

It allowed us to drill significantly shallower holes than before, saving cost on diamond drill bits and time drilling.