What is a cylindrical recess around a hole, typically to receive a bolt head or nut?

What is a cylindrical recess around a hole, typically to receive a bolt head or nut?

• A. Detail View
• B. Through Hole
• C. Broken-Out Section
• D. Counter Bore

Answer: (D)

A counterbore is a cylindrical recess around a hole that is designed to receive the head of a bolt or nut. It creates a larger-diameter pocket that goes to a specific depth, leaving a flat bottom so the fastener head sits flush with the surface. This is different from a through hole, which extends completely through the part, and from a countersink, which is a conical recess for a cone-shaped bolt head. The other terms refer to different drawing features rather than this recessed seat: a detail view highlights a small area with more detail, while a broken-out section shows interior features by removing material in the view.

A counterbore is a cylindrical recess around a hole that is designed to receive the head of a bolt or nut. It creates a larger-diameter pocket that goes to a specific depth, leaving a flat bottom so the fastener head sits flush with the surface. This is different from a through hole, which extends completely through the part, and from a countersink, which is a conical recess for a cone-shaped bolt head. The other terms refer to different drawing features rather than this recessed seat: a detail view highlights a small area with more detail, while a broken-out section shows interior features by removing material in the view.