In
machining,
boring is the process of enlarging a hole that has already been
drilled (or
cast), by means of a
single-point cutting tool (or of a boring head containing several such tools), for example as in boring a
gun barrel or an
engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to
turning, which cuts external diameters.