A peg with gear transmission, i.e., a mechanism for transmitting the peg's rotation to the string (mostly realized by gears). This allows a lighter and more precise tuning. The mechanism can either be open (with exposed worms, to facilitate lubrication or cleaning) or closed.

Tuning machines were invented in the 18th century and soon used for guitars. In 1927, Grover produced the first gear heads for ukuleles.

Pegs for Ukuleles are attached either to the sides of the head (with their wings sticking out laterally, as is the rule with Western or electric guitars) or to the back of the head (seen from the fretboard; as with most classical guitars).


Rear open tuning machine of a Pono MHTSH
Lateral closed tuning machine of a Oscar Schmidt OU 2


Tuning machines rarely break, but then they have to be replaced. For this, the small screws on the back of the top plate are released; thus loosen the entire assembly and replace it.