Machine Head — Lutherie Encyclopedia

Machine HeadType: glossaryA geared tuning mechanism mounted on the headstock that allows precise adjustment of string tension and pitch.## Definition A machine head, also known as a tuning machine, tuning peg, or tuner, is a geared mechanical device mounted on the headstock of a stringed instrument. It consists of a capstan (post) around which the string is wound, a worm gear and pinion mechanism that provides a mechanical advantage for fine pitch adjustment, and a button or knob that the player turns. The gear ratio, typically between 12:1 and 18:1 on guitars, determines how many turns of the button are needed for one rotation of the capstan. Higher ratios provide finer tuning control. Machine heads may be open-back (with visible gears) or sealed (enclosed in a housing with lubricant). They come in various configurations: individual units, three-on-a-plate sets for steel-string guitars, or integrated plates for classical guitars with slotted headstocks. ## In Practice Selecting machine heads involves balancing tuning precision, weight, aesthetics, and cost. Heavier tuners add mass to the headstock, which can affect sustain and neck balance. Lightweight tuners are preferred by many builders but are often more expensive. Installation requires drilling precisely sized and positioned holes in the headstock. Misaligned tuner holes can cause binding or poor string winding. On slotted headstocks, such as those on classical guitars, the tuner roller sits within the headstock slot, and the mounting plate is attached to the back face. On solid headstocks, the capstan protrudes through the front face. High-quality mac…