Tuning Machines (túnɪŋ mɪšín) is also known as “Machine Heads” or “Tuners”, which are the gear and shaft mechanisms used to attach the strings to the headstock of the guitar. Tuning machines have a knob (usually at a right angle to the tuner shaft) that, when turned, raises or lowers the attached string’s pitch. Tuners are usually made of chromed plated nickel-steel or brass and are sealed and self lubricating. A tuning machine’s gear ratio determines the level of tuning precision achievable without slipping. A higher ratio is usually preferable, as cheaper machine heads will often go out of tune more easily.