Counterbores & Port Tools
Counterbores (sometimes called spotfacers) create a flat-bottomed cavity at the top of an existing hole so that a bolt, nut, or other part is hidden beneath or sits flush with the top of the hole when installed into it. They may have a built-in pilot that cannot be removed, or they may have a removable pilot that can be replaced with pilots of different diameters to allow the tool to accomplish more tasks. Port tools contour an existing hole for a precise fit when installing ports in the hole. The pilot (or tip) of the counterbore or port tool should be the same diameter as the existing hole to keep the tool accurately centered during drilling. These tools are typically used in metalworking tasks.
