What is Counterbore
A counterbore is a cylindrical hole with a flat bottom that is drilled into a circuit board. It is specifically designed to accommodate socket head or hex head screws for fastening purposes. Unlike countersink holes, which can be drilled at various angles, counterbore holes can only be drilled at a single angle of zero degrees. This angle is chosen to maintain the efficiency of the hole.
A counterbore hole provides space for the screw head to sit flush with or below the surface of the PCB board, ensuring a secure and flush fastening. This allows for a neat and streamlined appearance of the board. Counterbore holes are typically used when a board requires the use of socket head or hex head screws for fastening. Counterbore holes are different from countersink holes in terms of shape. While countersink holes have a conical shape, counterbore holes are cylindrical with a flat bottom.