worm gear and worm wheel

The worm gear and worm wheel arrangement of gears seen above is called a worm and worm wheel. The worm, which in this example can be brown in colour, just has one tooth but it is similar to a screw thread. The worm wheel, coloured yellowish, is like a normal gear wheel or spur equipment. The worm at all times drives the worm wheel round, it is never the opposite way circular as the system tends to lock and jam