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 definitely brown in colour, only has one tooth but it is like a screw thread. The worm wheel, coloured yellow, is like a normal gear wheel or spur equipment. The worm always drives the worm wheel circular, it is never the contrary way round as the system tends to lock and jam