The manufacturing ways of worms are roughly divided among cutting, heat treated and plastic worm gear ground after cutting and rolling. And for worm wheels, they could be roughly divided among cutting tooth, cutting teeth after casting, and the teeth cutting after the exterior rim is normally cast around the guts of the blank.
As for the products for worm gears, for worms: structural carbon steel (S45C, etc.), structural alloy steel (SCM415, etc.), stainless and cast iron are used; and for worm wheels: cast iron (FC200, etc.), nonferrous metals such as phosphor bronze and specialty bronze (nickel bronze, metal bronze, etc.), engineering plastics such as MC Nylon, etc. As the combination of elements for worms and worm wheels impacts the allowable transmission drive and lubrication methods, the choice of mating elements requires consideration. Also, related to the friction of the teeth, 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 to ensure that the tooth thickness of the worm changes continuously in the axial way so that by shifting the worm axially with shims, it becomes possible to change the backlash.
If a worm equipment is used, a sizable speed reduction can be obtained in a concise space in comparison to using spur gears. Generally, the worm is utilized to carefully turn the worm steering wheel. But when the lead position is especially small, the worm steering wheel cannot turn the worm in fact it is referred to as its self locking feature. This can be used effectively in some applications but it can’t be called perfect preventative for reverse driving. (When the lead angle can be 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 for example low sound and vibration, but due to the significant sliding at the tooth areas (sliding contact), the performance is certainly low. (For cylindrical worm gears, the overall efficiency is about 30-90%.) Likewise, there are disadvantages such as they tend to have problems with tooth surface heating seizure.