Involute Spur Gear Builder (C) 2014 Dr. Rainer Hessmer

An open source, browser based utility for calculating and drawing involute spur gears. As an improvement over the majority of other freely available scripts and utilities it fully accounts for undercuts. For additional information please head over to my blog posts part 1 and part 2. If you prefer a standalone utility and you use Windows 64, see Doug Roger's port to C++.

The implementation is inspired by the subtractive process that Michal Zalewski's describes in part six of his excellent Guerrilla guide to CNC machining, mold making, and resin casting.


Specify desired values in the parameters box and then click on the 'Update' button. The tooth count n1 of gear one defines various configurations:

The tool also supports profile shift to reduce the amount of undercut in gears with low tooth counts.

The rendering of the gears can take a long time particularly if the quality parameters ('number of rotation steps' and 'number of segments per 360 degree' are increased. Dependent on your browser you might get a warning message indicating an unresponsive script. Allow the script to continue and eventually the gear rendering should show up. Once the gears show up you can use the mouse scroll wheel or the slider underneath the window to zoom in and out. For panning move the mouse while pressing the left mouse button.

The result can be saved as a DXF file by clicking the 'Generate DXF' button underneath the graphics window.

License and Credits