Forms of Teeth:

For the proof of the law of gearing, two bodies of common shape were considered. To have constant transmission of motion, two curves of any shape which fulfil law of gearing may be utilized for the profiles of teeth of two gears. On the other hand, profile of one of the mating tooth may be selected and profile of other tooth may be finding out by utilizing law of gearing. Such teeth are known as conjugate teeth. One profile that can be chosen arbitrarily shall be easy to manufacture but other profile that will follow law of gearing along with decided profile will be complicated to manufacture. Such teeth shall have high cost of manufacturing and replacement will be complicated. Because of these difficulties, requirement of standards for gear tooth profile was felt and curves that satisfy law of gearing were decided. The following curves satisfy law of gearing (1) Cycloid, and (2) Involute.