Machine head
The machine head is the part of a guitar or similar instrument and the end of the neck where strings are attached and where there is apparatus for tuning them. (There exist electric guitars where the tuners are on the body, and thus these guitars do not have a machine head.)
The machine head has pins, one per string. These pins have a hole, and the string is made to go through that hole, then is rolled around the pin. The strings is then tightened by turning the pin using a tuning knob; the link between the know and the pin is achieved by a worm gear. The worm gear ensures that the pin cannot turn without a movement on the knob; it also allows precise tuning. The guitar player, or an aide, adjusts the tension of the various strings using the knobs so that they are rightly tuned: a higher tension yields a more treble sound, a lower tension a graver sound.
There exist two main different kinds of machine head apparatus:
- on "classical", nylon-string guitars, the worm gears are generally apparent; the strings are rolled on the pins inside grooves in the head;
- on steel-string guitars, including "folk" acoustic guitars and electric guitars, the worm gears are generally placed in sealed enclosures with permanent lubrication; there exist several possible shapes of the head:
- rectangular head, 2 rows of 3 pins (or 6 pins for 12-string guitars): found on most "folk" guitars and on Gibson Les Paul guitars;
- a single diagonal row of 6 pins: found on Fender Telecaster and Stratocaster guitars.