COUNTERSINKS

Noun

countersinks

plural of countersink

Verb

countersinks

Third-person singular simple present indicative form of countersink

Source: Wiktionary

COUNTERSINK

Coun"ter*sink` (koun"tr-sk`; 277), v. t. [imp. & p. p. Countersunk (- s; 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.

Note: 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.

Source: Webster’s Unabridged Dictionary 1913 Edition