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[v., n. koun-ter-singk; v. also koun-ter-singk] /v., n. ˈkaʊn tərˌsɪŋk; v. also ˌkaʊn tərˈsɪŋk/
verb (used with object), countersank, countersunk, countersinking.
to enlarge the upper part of (a cavity), especially by chamfering, to receive the cone-shaped head of a screw, bolt, etc.
to cause (the head of a screw, bolt, etc.) to sink into a prepared depression so as to be flush with or below the surface.
a tool for countersinking a hole.
a countersunk hole.
Origin of countersink
1810-20; counter- + sink Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for countersunk
Historical Examples
  • A grinning soldier seized a countersunk ring and raised the trap-door.

    The Martian Cabal Roman Frederick Starzl
  • Two holes are bored and countersunk for screws to hold the post and handle.

    Mission Furniture H. H. Windsor
  • The taper bolts should be of steel, but those with countersunk heads may be of iron.

  • Holes are bored and countersunk at the places shown in the drawing.

    Toy Craft Leon H. Baxter
  • Small carriage bolts are better than nails but the heads should be countersunk into the bottom with the points up.

    Farm Mechanics Herbert A. Shearer
  • On top the holder is spotted or countersunk with a drill to form a recess for the C-clamp.

    Measuring Tools Unknown
  • Their heads and nuts are let into countersunk holes so that no part will extend above the surface of the pulley.

  • It is fastened on with screws, the heads of which are countersunk.

  • As this process reverses the hinge, the screw holes must be countersunk on the opposite side.

  • It consists of a steel shaft coned at both ends running between two countersunk bearings, one of which is adjustable.

British Dictionary definitions for countersunk


verb (transitive) -sinks, -sinking, -sank, -sunk
to enlarge the upper part of (a hole) in timber, metal, etc, so that the head of a bolt or screw can be sunk below the surface
to drive (a screw) or sink (a bolt) into such an enlarged hole
Also called countersink bit. a tool for countersinking
a countersunk depression or hole
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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