How to Counter Boring and Drilling

Counter boring and drilling are techniques that can be used in a variety of applications. They can be used to create a hole that is bigger in diameter than a previous hole or make the existing hole smaller, as well as allowing screws and bolts to sit flush with the surface of the workpiece.

Typically, a counterbore tool is used for creating a hole for the fastener’s body and its head, but sometimes a counterboring bit can also be used to enlarge the hole in a piece of wood to allow a screw to fit without protruding above the surface of the wood.

A counterbore cutter, which is similar to a drill bit, has a small pilot portion that fits into a pre-drilled hole and guides the counterbore, so it must be aligned correctly with the original hole. This is necessary to prevent the counterbore from being too large for the fastener it is supposed to fit.

Another way to counter bore is to use a Forstner type of drill bit, which has a smaller center point than the hole it is drilling. This will leave a shallower hole that is easier to counter bore with a larger Forstner bit.

It is also useful in avoiding extra long screws in certain situations where you need to join two pieces of wood together, but the first board is wider than the second. This is often done with a counterbore partway through the larger board, then a smaller screw that passes entirely through the narrower board.