worm gear and worm wheel

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