BOLT ON NECK
The development of the bolt on solution for linking a neck to a guitar body dates back to the 50's and gained popularity thanks to
Leo Fender who used it due to it's ease and flexibility in mass production.
A bolt on neck is fixed to a guitar body thorough 4 or more bolts which can be directly bolted into the wood or into sunken counter threads.
The bolts may lay on a screw plate or on special ferrules leveled to the wood.
The advantage of having a removable neck is that if for some reason the neck gets damaged it can easily be replaced and there is more room for setup and adjustments.
A bolt on instrument is also much more easy to manufacture than a neck through one.
The psychologycal and practical aspect of the above, brought the bolt on solution into vast use on both cheap and very expensive instruments.
Sound wise the bolt on method allows the body to be built from one single piece of wood, which if the neck is well matched (read "tuned") to the body resonance, may bring some tone improvement.
The neck joint also plays a crucial role in a bolt on instruments tone and resonance.
To allow a perfect transmission of vibration from the neck to the body, both of them must fit perfectly together in the neck joint cut, on all sides, and finish should be removed at least from the bottom of the neck cut, if not also from under the neck itself. This will make a bolt on sound almost like a set neck and dramatically improve tone.
electric guitar construction.
The reason why we almost see H/S/S or S/S/S pickup configuration on bolt on instruments does not relate to the single coil pickup design itself.
Single coil pickup sound wonderful on every kind of instrument.
The fact Leo Fender choose this construction method for his guitars and used most of all single coil pickup
has brought the single coil design to be "linked" to the bolt on design rather
than other different and still valuable types of neck joint.
On the other hand 70 years of electric guitar has trained our ears to the tone of an alder body, a bright
maple neck and a single coil pickup, so I think this trend will last for many many years to come.
To facilitate the reaching of the higher frets on bolt on necks, luthiers and builders developed a variety of solutions called "contoured neck heel". This is obtained by carving the neck heel area on the body side in various different ways and by bolting the neck using four ferrules instead of a neck plate (photo below).