countersink

(ko̵untər siŋk′)

transitive verb countersunk, countersinking

  1. to enlarge the top part of (a hole in metal, wood, etc.) so that the head of a bolt, screw, etc. will fit flush with or below the surface
  2. to sink the head of (a bolt, screw, etc.) into such a hole

noun

  1. a bit for countersinking holes
  2. a countersunk hole

See countersink in American Heritage Dictionary 4

noun
  1. A hole with the top part enlarged so that the head of a screw or bolt will lie flush with or below the surface.
  2. A tool for making such a hole.
transitive verb coun·ter·sunk (-sŭngkˌ), coun·ter·sink·ing, coun·ter·sinks
  1. To make a countersink on or in.
  2. To drive (a screw or bolt) into a countersink.

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countersink

single-flute countersink bit

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countersink

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