There are three ways of attaching the neck to the body of an electric guitar: set necks where the neck is glued to the body with a tenon joint (most Gibson guitars), though necks where the neck & body are made from the same piece of wood and bolt-on necks (most Fender guitars).

This project by John Williams shows how you can make a guitar neck using a home-built CNC machine. John built the CNC machine with plans and a kit from HobbyCNC.com. (Check out www.cnczone.com for free plans).