Expanding bit

from The Collaborative International Dictionary of English v.0.48

Expanding \Ex*pand"ing\, a.
   That expands, or may be expanded; extending; spreading;
   enlarging.
   [1913 Webster]

   {Expanding bit}, {Expanding drill} (Mech.), a bit or drill
      made adjustable for holes of various sizes; one which can
      be expanded in diameter while boring.

   {Expanding pulley} (Mach.), a pulley so made, as in sections,
      that its diameter can be increased or diminished.
      [1913 Webster]