The manufacturing methods of worms are roughly divided among cutting, heat treated and ground after cutting and rolling. And for worm wheels, they may be approximately divided among cutting tooth, cutting the teeth after casting, and the teeth cutting after the exterior rim is certainly cast around the center of the blank.
As for the elements for worm gears, for worms: structural carbon metal (S45C, etc.), structural alloy metal (SCM415, etc.), stainless and cast iron will be utilized; and for worm tires: cast iron (FC200, etc.), non-ferrous metals such as phosphor bronze and specialized bronze (nickel bronze, metal bronze, etc.), engineering plastics such as MC Nylon, etc. As the combination of elements for worms and worm tires influences the plastic worm gear allowable transmission drive and lubrication strategies, the choice of mating supplies requires consideration. Also, related to the friction of tooth, a harder material for worm than worm steering wheel is generally used.
Ordinarily the lead angles of the proper and remaining tooth surface of a worm are the same. Yet, in duplex worm gears, they are made in order that the tooth thickness of the worm changes continuously in the axial direction so that by shifting the worm axially with shims, it turns into possible to modify the backlash.
If a worm equipment is used, a big speed decrease can be acquired in a compact space in comparison to using spur gears. Generally, the worm is utilized to carefully turn the worm steering wheel. However when the lead position is especially small, the worm steering wheel cannot turn the worm and it is known as its self locking characteristic. This can be used effectively in a few applications but it can not be called ideal preventative for reverse driving. (When the business lead angle is normally large, you’ll be able to turn the worm with the worm wheel.) In addition, there are many advantages to worm gears such as for example low noises and vibration, but as a result of the significant sliding at the tooth floors (sliding contact), the effectiveness is definitely low. (For cylindrical worm gears, the overall efficiency is about 30-90%.) 
Likewise, there are down sides such as for example they tend to have problems with tooth surface heating seizure.