As any well-versed worm gear manufacturer will tell you, worm gears are those ones with the circular, toothed wheels that have a spiral thread sitting on top that both engages and drives the wheel. Folks that don’t work with gears don’t realize that this basic interaction between two pieces is one of the world’s “six simple machines.” Typically, they’re comprised of steel and brass.
The way that worm gears work, generally, is when either an engine or electric motor is used to apply some rotational power to the worm, which then rotates again the wheel. Worm gears get chosen over standard gears for several reasons. One of them is that it’s impossible to reverse the direction of power – applying force to the wheel will not get the worm turning the same way that the process works in reverse. On standard gears, conversely, input and output can be turned independently once pressure is applied. A backstop must be added to a standard gearbox to prevent this. Another reason for choosing a worn gear is something called a high reduction ratio – worm gears can actually have very large reduction ratios with very little effort involved, which means it can be used to greatly reduce speed or dramatically increase torque. The end result is that worm gear users are generally operating with fewer moving parts and therefore have less margin of error.
Sounds ideal for any number of tasks, right? Well, yes and no. Worm gears offer more with less insofar as actually moving parts are concerned, and this does indeed cut on the complexity of a given gear structure – but worm gears also require very special lubricants to maintain operation. the wheel and the worm’s tandem movement is based solely on sliding, which is facilitated via high viscosity lubricants that must be available on-site at all times. These lubricants are apparently challenging to filter and highly specialized.
A worm gear manufacturer can clue you in as to the gear’s best applications and when using a standard gear, bevel gear, spur gear, or some sort of custom gears would be a better bet.