Without things like pinion gears, spur gears and worm gear manufacturers, many machines would not be able to operate. Gears are what allow some machines to run the way they were designed to. Some machines require custom made gears, although custom gears are typically for specialized purposes or custom machines. Ultimately, in most mechanical devices, gears are what allow the entire thing to work.
The rack and pinion gear set is the one most typically used to operate locomotives on a track. Bicycles too have gears which are instrumental to how they operate. Gears operate in a simple manner; a gear or cogwheel is a circular piece of metal with teeth, which is then meshed with another gear or piece of machinery which allows for torque to be transmitted. Gears can be either a part of a simple mechanism or complex mechanism, depending on how many different pieces of machinery are used.
Bevel gear manufacturers are incredibly important to the creation of gears; bevel gears are typically used on shafts mounted at 90 degree angles. In straight bevel gears, the teeth are straight, and parallel to the generators of the core. When you change the amount of teeth on a bevel gear, it allows for the mechanical advantage to be manipulated as well. Bevel gear manufacturers are most important in the use of hand drills, although power plants, railway track inspection machines, locomotives, printing presses and even automobiles and locomotives rely on bevel gears.