They connect parallel shafts, have involute teeth that are parallel to
the shaft and can have internal or external teeth. They cause no
external thrust between gears. They are inexpensive to manufacture. They
give lower but satisfactory performance. They are used when shaft
rotates in the same plane. The main features of spur gears are dedendum, addendum, flank, and fillet. Dedendum cylinder is a root from where teeth extend, it extends to the tip called the addendum circle. Flank or the face contacts the meshing gear, the most useful feature if the spur gears. The fillet in the root region is kinetically irrelevant.
Characteristics
The speed and change of the force depends on the gear ratio, the ratio of number of teeth on the gears that are to be meshed. One gear among the two is on the input axle, the axle of the motor and the other gear of the pair is on the output axle, the axle of the wheel.
They have higher contact ratio that makes them smooth and quiet in operation. They are available for corrosion resistant operation. They are among the most cost-effective type of gearing. They are also used to create large gear reductions.
Materials
They are available in plastic, non-metallic, brass, steel and cast iron and are manufactured in a variety of styles. They are made with many different properties. Factors like design life, power transmission requirements, noise and heat generation, and presence of corrosive elements contribute to the optimization of the gear material.
Applications
Generally used in simple machines like washing machines, clothes dryer or power winches. They are not used in automobiles because they produce sound when the teeth of both the gears collide with each other. It also increases stress on the gear teeth. They are also used in construction equipment, machine tools, indexing equipment, multi spindle drives, roller feeds, and conveyors.