What is a counterbore used for?

A counterbore is specifically designed to create a cylindrical recess around a hole. This recess allows for the head of a fastener, like a bolt or screw, to sit below the surface of the material or even be flush with it. This is especially useful in applications where a smooth surface is desired for aesthetic purposes or to avoid catching on moving parts. It also helps to distribute the load of the fastener evenly, reducing stress concentrations around the hole. The counterbore's design serves practical purposes in assembly and functionality, effectively accommodating specific fasteners while ensuring a neat finish on the assembled parts.