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Basic Gear Terminology

December 07, 2020

Basic Gear Terminology

Gear manufacturing can be a complex process requiring a variety of advanced machinery. The best gear manufacturers, like True Gear & Spline, make sure to keep an inventory of the best machinery to stay on top of the latest developments in gears. Learning the basic gear terminology will help you understand how efficient gears are designed for different end use applications. Specifically, the dimensions of gears are calculated based on these three elements: module, pressure angle, and the number of teeth.


The following are some of the basic terminology in the world of gear manufacturing:



Module refers to the size of the gear or how big or small it is. Basically, it is the ratio of the reference diameter of a gear divided by the number of teeth, and is expressed in millimeters (mm).


Diametral Pitch

Diametral pitch or the reciprocal of the module is the ratio of the number of a gear’s teeth to its pitch circle diameter and is expressed in “teeth per inch”.


Pressure Angle

The pressure angle is one key that will help you determine the tooth profile. It refers to the leaning angles of a gear tooth. Today, pressure angles are usually set at either 20° or 14.5°.


Number of Teeth

The number of teeth refers to the number of gear’s teeth. These can vary based on the required end use applications.



Addendum refers to the height by which a gear tooth projects either from outside (external) or inside (internal). It could also refer to the distance between the reference line and the tooth tip.



Dedendum is larger than the addendum and is the distance between the reference line and the tooth root.


Tooth Depth

Tooth depth, determined from the size of the module, refers to the distance between the tooth tip and the tooth root or the sum of the addendum and the dedendum.


Indeed, knowing the technical terms of gear manufacturing can help you choose the best gear size, strength, and other factors for your needs. With that said, the experts at True Gear and Spline will help you choose the best gears through a proper consultation. Check out our website to learn more about us!