Collet

n.
  1. A small collar or neckband.
  2. (Mech.) A small metal ring; a small collar fastened on an arbor; as, the collet on the balance arbor of a watch; a small socket on a stem, for holding a drill.
    1. The part of a ring containing the bezel in which the stone is set.
    2. The flat table at the base of a brilliant. See Illust. of Brilliant.