Noun
worm gear (plural worm gears)
The gear in a worm drive.
His device had the camera mounted on a vertical axis that could be rotated by a worm gear driven by turning a crank handle, and Paul put it on general sale the next year. Source: Internet
The banjo is usually tuned with friction tuning pegs or planetary gear tuners, rather than the worm gear machine head used on guitars. Source: Internet
The key on the tuning machine turns a metal worm, which drives a worm gear that winds a string. Source: Internet