The manufacturing ways of worms are roughly divided among cutting, heat treated and ground after cutting and rolling. And 
for worm wheels, they could be approximately divided among cutting the teeth, cutting tooth after casting, and teeth cutting after the outside rim is usually cast around the center of the blank.
As for the products for worm gears, for worms: structural carbon steel (S45C, etc.), structural alloy metal (SCM415, etc.), stainless and cast iron happen to be used; and for worm tires: cast iron (FC200, etc.), non-ferrous metals such as for example phosphor bronze and specialized bronze (nickel bronze, aluminium bronze, etc.), engineering plastics such as MC Nylon, etc. Because the combination of supplies for worms and worm plastic worm gear wheels affects the allowable transmission force and lubrication methods, the decision of mating materials requires careful consideration. Also, related to the friction of tooth, a harder material for worm than worm wheel is generally used.
Ordinarily the lead angles of the right and left tooth surface of a worm will be the same. Yet, in duplex worm gears, they are created in order that the tooth thickness of the worm improvements continually in the axial way to ensure that by shifting the worm axially with shims, it becomes possible to change the backlash.
If a worm gear is used, a sizable speed lowering can be acquired in a compact space compared to using spur gears. Generally, the worm is utilized to carefully turn the worm wheel. But when the lead angle is particularly small, the worm steering wheel cannot turn the worm and it is known as its self locking characteristic. This can be utilised effectively in a few applications but it can not be called best preventative for invert driving. (When the lead angle is certainly large, you’ll be able to switch 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 performance is certainly low. (For cylindrical worm gears, the overall efficiency is about 30-90%.) Also, there are drawbacks such as they tend to have problems with tooth surface heating seizure.