worm gear and worm wheel

The arrangement of gears seen above is worm gear and worm wheel called a worm and worm wheel. The worm, which in this example is brown in colour, only has one tooth nonetheless it is similar to a screw thread. The worm wheel, coloured yellowish, is like a standard equipment wheel or spur equipment. The worm always drives the worm wheel round, it is never the opposite way round as the system will lock and jam