What is a Counterbore Hole?
A counterbore hole is a cylindrical recess on a PCB that has a larger diameter at the top surface and a smaller diameter at the bottom. The purpose of a counterbore hole is to create space for a screw head or a boltâ??s flange, allowing it to sit flush with or slightly below the PCB surface. The larger diameter at the top accommodates the head or flange, while the smaller diameter ensures that the fastenerâ??s shaft or body fits snugly.

What is a Countersunk Hole?
On the other hand, a countersunk hole is a conical recess on a PCB that allows the head of a screw or bolt to sit flush with the PCB surface. The shape of a countersunk hole matches the profile of the fastenerâ??s head, creating a seamless and level surface when the screw or bolt is fully inserted. Countersunk holes typically have an angled side, often 82 or 90 degrees, which determines the shape and size of the fastener head that will fit into the recess.