countersunkhead

A countersunk head is a type of screw head designed to sit flush with or below the surface of the surrounding material when installed in a countersunk hole. The head is conical (or sometimes pyramidal) on the underside, so it can seat evenly against a matching conical hole, distributing load over a broader area and reducing protrusion.

The hole prepared for a countersunk screw is machined with a countersink that mirrors the head’s angle. Common standard angles are around 82 degrees in many systems, though some applications use angles nearer to 90 degrees. Countersunk screws are typically referred to by their drive type (for example, slotted, Phillips, Pozidriv, Torx) in addition to the countersunk head designation.

Materials and finishes for countersunk screws vary widely. They are commonly made from steel, stainless steel, brass, or aluminum, and may be finished with zinc plating, black oxide, nickel, or other coatings to improve wear resistance and corrosion performance. They are widely used in woodworking, cabinetry, furniture, electronics enclosures, and metal assemblies where a flat, snag-free surface is desired.

Installation requires appropriate preparation: a correct pilot hole and countersink to match the screw diameter and head angle, proper seating without over-tightening, and sufficient thread engagement for the material. Inadequate countersinking or overtightening can cause material damage or a head that is not fully flush.

Compared with other head styles, countersunk screws provide a flush profile but may require more precise hole preparation and can offer different load characteristics, particularly near the head under high shear or pull-out conditions.