Coun"ter*sink` (koun"t&etilde;r*s&ibreve;&nsm;k`;
277), v. t. [imp. & p. p.
Countersunk (-sŭ&nsm;k`); p. pr. & vb.
n. Countersinking.] 1. To
chamfer or form a depression around the top of (a hole in wood,
metal, etc.) for the reception of the head of a screw or bolt
below the surface, either wholly or in part; as, to
countersink a hole for a screw.
2. To cause to sink even with or below
the surface; as, to countersink a screw or bolt into
woodwork.
Coun"ter*sink`, n.
1. An enlargement of the upper part of a
hole, forming a cavity or depression for receiving the head of a
screw or bolt.
&fist; In the United States a flaring cavity formed by
chamfering the edges of a round hole is called a
countersink, while a cylindrical flat-bottomed enlargement
of the mouth of the hole is usually called a
conterbore.
2. A drill or cutting tool for
countersinking holes.
