SG Heritage Dictionary

Countersink [Noun] Webster's Dictionary 1913

1. An enlargement of the upper part of a hole, forming a cavity or depression for receiving the head of a screw or bolt.

2. A drill or cutting tool for countersinking holes.

Countersink [Verb transitive] Webster's Dictionary 1913

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.

Countersinking [Present participle and verbal noun] Webster's Dictionary 1913

of Countersink