There are a number of different kinds of gears available in the market, manufactured according to material, shafts, sizes and so on, all designed depending on its purpose. There are different criteria used to classify each type of gear, a popular method is categorizing them according to the arrangement of shaft or axle. There are for 3 kinds of shaft arrangement, namely parallel shafts, intersecting shafts and non-intersecting or non-parallel axis.
Before launching to further discussion though, let me first define a 'gear'. In layman's term, a gear is a cylindrically shaped toothed wheel that serves as a mechanism to transmit reciprocating or rotational motion from one part of a machine to another. Furthermore when there are two or more gears working with each other the connection between these gears allows power flow from one gear shaft or axle to another.
First, parallel shaft gears are the type of gears that interlock in the same surface level. Examples are spur or straight-cut (simplest type of gear), helical (simple helical gear and herringbone or double helical gear). They function as a mechanism to transfer power of rotational motion between the parallel shafts. The advantages are these gears provide maximum horsepower designed for long-term efficiency. Also, it can carry a high load and does not make much noise when it operates. On the other hand, production of these types of gear is expensive and creates axial thrust. These gears are generally used for machines with manual transmissions like clock, car steering and more.
Second, intersecting shaft gears are designed to allow smooth transfer of power and motion between axes that are angled to be perpendicular with each other. The following are types of gears that fall into this category: bevel (miter, straight bevel, spiral bevel, and zero bevel or zero), coniflex, angular and crown gear. There purpose is to power machines that require speed and strength because it can handle high load capacity. Compared to parallel shaft, intersecting gears are more inexpensive. These types of gears are typically used to power hand drills, locomotives, marine applications and much more.
Lastly, non-intersecting or non-parallel shaft gears are used on applications that require high-ratio speed reduction that can provide power transmission within a limited area while using gears with non-intersecting axes. Although it is the most inexpensive type of gear, because its production cost is also the lowest, it has a limited load capability. This setback can be easily solved by lowering the ratios to increase efficiency. Examples of nonintersecting shaft gears are crossed-helical, worm and hypoid. These are commonly seen on passenger lifts, electric mixer, sprinkler, rear axles of busses and other heavy vehicles among others.
This is only one many systems that categorizes the use of gears. Some categorizes gears according pitch diameter, materials used to manufacture the gear, manufacturing precision, number of steps and housing design among others. The purpose of these systems is to provide the consumer the information they need to help them purchase the most ideal gear according to their needs. Also, these give them a basis for criteria.
