What is Countersink?

What is Countersink?

• A. Has internal threads
• B. A conical-shaped recess around a hole, often used to receive a tapered screw.
• C. A line used to show the alternate positions of an object without interfering with the main drawing.
• D. The ratio between two quantities.

Answer: (B)

A countersink is a conical-shaped recess around a hole that is created to receive a tapered screw head so the screw sits flush with or below the surface. This feature lets the screw head sit neatly without protruding, giving a smooth finish and proper seating for flat-head or countersunk screws. In drawings, a cone around the hole indicates this recessed seating area. It’s different from a threaded hole, which simply contains internal threads for a screw or bolt, from a line used to show alternate positions, or from a ratio, which is a measurement relation rather than a physical feature. For contrast, remember that a counterbore is a cylindrical recess for a screw head, whereas a countersink is conical.

A countersink is a conical-shaped recess around a hole that is created to receive a tapered screw head so the screw sits flush with or below the surface. This feature lets the screw head sit neatly without protruding, giving a smooth finish and proper seating for flat-head or countersunk screws. In drawings, a cone around the hole indicates this recessed seating area. It’s different from a threaded hole, which simply contains internal threads for a screw or bolt, from a line used to show alternate positions, or from a ratio, which is a measurement relation rather than a physical feature. For contrast, remember that a counterbore is a cylindrical recess for a screw head, whereas a countersink is conical.