The manufacturing methods of worms are roughly divided among cutting, heat treated and ground after cutting and rolling. And for worm wheels, they might be approximately divided among 
cutting teeth, cutting tooth after casting, and pearly whites cutting after the outside rim can be 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.), plastic worm gear stainless steel and cast iron will be applied; 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 wheels influences the allowable transmission force and lubrication methods, the choice of mating components requires consideration. Also, linked to the friction of pearly whites, a harder material for worm than worm steering wheel is generally used.
Ordinarily the lead angles of the proper and kept 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 alterations constantly in the axial way to ensure that by shifting the worm axially with shims, it becomes possible to modify the backlash.
If a worm equipment is used, a large speed decrease can be obtained in a compact space in comparison to using spur gears. Generally, the worm can be used to carefully turn the worm wheel. But when the lead position is especially small, the worm steering wheel can not turn the worm and it is called its self locking feature. This can be utilized effectively in a few applications but it can not be called perfect preventative for reverse driving. (When the business lead angle is definitely large, you’ll be able to change the worm with the worm steering wheel.) In addition, there are many advantages to worm gears such as low noise and vibration, but as a result of the significant sliding at the tooth floors (sliding contact), the proficiency is normally low. (For cylindrical worm gears, the overall efficiency is approximately 30-90%.) Likewise, there are drawbacks such as they tend to suffer from tooth surface high temperature seizure.