lighter screw

from The Collaborative International Dictionary of English v.0.48
Lighter \Light"er\, n. [D. ligter, fr. ligt light. See {Light}
   not heavy.] (Naut.)
   A large boat or barge, mainly used in unloading or loading
   vessels which can not reach the wharves at the place of
   shipment or delivery.
   [1913 Webster]

   {Lighter screw} (Mach.), a screw for adjusting the distance
      between the stones in a grinding mill by raising or
      lowering the bridgetree.
      [1913 Webster]
    

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