![design - Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly? - Engineering Stack Exchange design - Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly? - Engineering Stack Exchange](https://www.unf.edu/~aschonni/Research/design%20analys%20fabr%20verific/gear%20tooth/Gear_design_analysis_files/image005.jpg)
design - Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly? - Engineering Stack Exchange
Consider two "friction" wheels - a Pinion driving a Gear through contact of their outer diameters. The speed ratio is
![design - Involute gear curve when root diameter falls below base diameter - Engineering Stack Exchange design - Involute gear curve when root diameter falls below base diameter - Engineering Stack Exchange](https://i.stack.imgur.com/YafhH.png)