This project is a html and javascript based change gear calculator for threading operations on lathes. Individual lathe setups can be "saved" by bookmarking the link to the calculation. The calculator can also be used offline by simply saving the webpage including resources (link below) to the computer and accessing it from that location. Calculations are performed in a non-blocking manner with progress update written to the page regularly. The results are sorted by how well they match the desired lead.
The calculator is made to be compatible and usable for both desktop and mobile users. An effort was made to allow the calculator to be used also on a few years old browsers, such that might be found in a garage computer.
Let me know in case you have some improvement suggestions.
The calculator can be tested and used at https://finngineering.com/changegears.html