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), through necks where the neck & body are made from the same piece of wood and bolt-on necks (most Fender guitars). It is almost a given amongst guitar players, that through necks sustain better than set-necks and bolt-on necks have the worst sustain.
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). The software used was: Rhino 3D to design the neck, MeshCAM to generate the tool paths for the maching process and TurboCNC to operate the machine.