worm gear and worm wheel

The arrangement of gears seen above is called a worm and worm wheel. The worm, which in this worm gear and worm wheel example is certainly brown in colour, only has one tooth nonetheless it is like a screw thread. The worm wheel, coloured yellow-colored, is like a normal gear wheel or spur gear. The worm often drives the worm wheel round, it is never the contrary way round as the system will lock and jam