triblet

from The Collaborative International Dictionary of English v.0.48

Triblet \Trib"let\, Tribolet \Trib"o*let\, n.] [F. triboulet.]
   1. A goldsmith's tool used in making rings. --Ainsworth.
      [1913 Webster]

   2. A steel cylinder round which metal is drawn in the process
      of forming tubes. --Tomlinson.
      [1913 Webster]

   3. (Blacksmithing) A tapering mandrel.
      [1913 Webster]