Tuners: Tuners are also termed as machine heads and tuning pegs. These bits are twisted to tune your guitar. The key part which is flat is joined where the string is wound. When you tighten or loosen these bits, it helps in changing the tension in strings and as a result, it helps to change the pitch. These bits are also known as guitar tuner buttons and one must replace the old and dirty guitar tuning pegs with new ones.