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 definitely brown in colour, only has one tooth nonetheless it is like a screw thread. The worm wheel, coloured yellowish, is like a standard equipment wheel or spur gear. The worm generally drives the worm wheel circular, it is never the worm gear and worm wheel opposite way circular as the system will lock and jam