A countersunk hole is defined as which of the following?

• A. A hole tapered or beveled around its edge to allow a rivet or bolt head to seat flush with or below the surface of the object.
• B. A hole with a rounded bottom.
• C. A hole threaded for a bolt.
• D. A hole used to align parts.

Answer: (A)

A countersunk hole is a hole that has a tapered or beveled edge around it so that the head of a flat-headed fastener can sit flush with or below the surface of the object. This is created to create a smooth surface and prevent the fastener head from protruding, which is why flat-headed screws or rivets are used with this feature. It’s different from a hole with a rounded bottom (which isn’t designed to seat a fastener head), a threaded hole (which provides internal threads for a bolt), or an alignment hole (which is meant to position parts rather than accept a fastener head).