A countersink is a conical hole cut into a workpiece, or the cutter used to cut it, most often made so the head of a countersunk screw, bolt or rivet can sit flush with or below the surrounding surface once driven home. Compared to a counterbore, which cuts a flat-bottomed hole for a socket-head fastener, a countersink's cone shape matches the underside of a flat or oval fastener head; it is also used simply to remove the sharp burr a drilling or tapping operation leaves behind.
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Introduced When (Circa)Not established by the cited source.
Countersink (Wikipedia) describes the tools geometry, types and machining use but gives no date or era for when the countersink was introduced; checked fresh 2026-09-17 against the raw article extract. OriginNot established by the cited source.
Countersink (Wikipedia) gives no origin story or inventor, only a technical description of the tools geometry and machining use; checked fresh 2026-09-17 against the raw article extract. Connections
Used In
Source Popular Woodworking: Woodworking Glossary
Sources
1. Countersink (Wikipedia)
Lead section
In manufacturing, a countersink (symbol: ⌵) is a conical hole cut into a manufactured object, or the cutter used to cut such a hole.
Lead
or the cutter used to cut such a hole
View the SourceWikidata: Countersink
Wikidata Q15148168, class allow-list match, case-insensitive label variant (w-bbfill-smallsix2-0926/resolve_ci.ps1)View the Source Popular Woodworking: Woodworking Glossary
Popular WoodworkingUsed In: Woodworking, Glossary entryQuote, Used In: Woodworking, Glossary entry
To cut a cone-shaped recess in a pilot or clearance hole that allows a flat-head screw to seat flush or below the surface
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