Topic summary
Tuning Machine
Extracted from the Wikipedia article Machine head.
A machine head (also referred to as a tuning machine, tuner, or gear head) is a geared apparatus for tuning stringed musical instruments by adjusting string tension. Machine heads are used on mandolins, guitars, double basses, and others, and are usually located on the instrument's headstock. Other names for guitar tuners include pegs, gears, machines, cranks, knobs, tensioners, and tighteners.