worm gear and worm wheel

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